drm/i915: Refactor common ringbuffer allocation code

[android-x86/kernel.git] / drivers / gpu / drm / i915 / intel_lrc.c

/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Ben Widawsky <ben@bwidawsk.net>
 *    Michel Thierry <michel.thierry@intel.com>
 *    Thomas Daniel <thomas.daniel@intel.com>
 *    Oscar Mateo <oscar.mateo@intel.com>
 *
 */

/**
 * DOC: Logical Rings, Logical Ring Contexts and Execlists
 *
 * Motivation:
 * GEN8 brings an expansion of the HW contexts: "Logical Ring Contexts".
 * These expanded contexts enable a number of new abilities, especially
 * "Execlists" (also implemented in this file).
 *
 * One of the main differences with the legacy HW contexts is that logical
 * ring contexts incorporate many more things to the context's state, like
 * PDPs or ringbuffer control registers:
 *
 * The reason why PDPs are included in the context is straightforward: as
 * PPGTTs (per-process GTTs) are actually per-context, having the PDPs
 * contained there mean you don't need to do a ppgtt->switch_mm yourself,
 * instead, the GPU will do it for you on the context switch.
 *
 * But, what about the ringbuffer control registers (head, tail, etc..)?
 * shouldn't we just need a set of those per engine command streamer? This is
 * where the name "Logical Rings" starts to make sense: by virtualizing the
 * rings, the engine cs shifts to a new "ring buffer" with every context
 * switch. When you want to submit a workload to the GPU you: A) choose your
 * context, B) find its appropriate virtualized ring, C) write commands to it
 * and then, finally, D) tell the GPU to switch to that context.
 *
 * Instead of the legacy MI_SET_CONTEXT, the way you tell the GPU to switch
 * to a contexts is via a context execution list, ergo "Execlists".
 *
 * LRC implementation:
 * Regarding the creation of contexts, we have:
 *
 * - One global default context.
 * - One local default context for each opened fd.
 * - One local extra context for each context create ioctl call.
 *
 * Now that ringbuffers belong per-context (and not per-engine, like before)
 * and that contexts are uniquely tied to a given engine (and not reusable,
 * like before) we need:
 *
 * - One ringbuffer per-engine inside each context.
 * - One backing object per-engine inside each context.
 *
 * The global default context starts its life with these new objects fully
 * allocated and populated. The local default context for each opened fd is
 * more complex, because we don't know at creation time which engine is going
 * to use them. To handle this, we have implemented a deferred creation of LR
 * contexts:
 *
 * The local context starts its life as a hollow or blank holder, that only
 * gets populated for a given engine once we receive an execbuffer. If later
 * on we receive another execbuffer ioctl for the same context but a different
 * engine, we allocate/populate a new ringbuffer and context backing object and
 * so on.
 *
 * Finally, regarding local contexts created using the ioctl call: as they are
 * only allowed with the render ring, we can allocate & populate them right
 * away (no need to defer anything, at least for now).
 *
 * Execlists implementation:
 * Execlists are the new method by which, on gen8+ hardware, workloads are
 * submitted for execution (as opposed to the legacy, ringbuffer-based, method).
 * This method works as follows:
 *
 * When a request is committed, its commands (the BB start and any leading or
 * trailing commands, like the seqno breadcrumbs) are placed in the ringbuffer
 * for the appropriate context. The tail pointer in the hardware context is not
 * updated at this time, but instead, kept by the driver in the ringbuffer
 * structure. A structure representing this request is added to a request queue
 * for the appropriate engine: this structure contains a copy of the context's
 * tail after the request was written to the ring buffer and a pointer to the
 * context itself.
 *
 * If the engine's request queue was empty before the request was added, the
 * queue is processed immediately. Otherwise the queue will be processed during
 * a context switch interrupt. In any case, elements on the queue will get sent
 * (in pairs) to the GPU's ExecLists Submit Port (ELSP, for short) with a
 * globally unique 20-bits submission ID.
 *
 * When execution of a request completes, the GPU updates the context status
 * buffer with a context complete event and generates a context switch interrupt.
 * During the interrupt handling, the driver examines the events in the buffer:
 * for each context complete event, if the announced ID matches that on the head
 * of the request queue, then that request is retired and removed from the queue.
 *
 * After processing, if any requests were retired and the queue is not empty
 * then a new execution list can be submitted. The two requests at the front of
 * the queue are next to be submitted but since a context may not occur twice in
 * an execution list, if subsequent requests have the same ID as the first then
 * the two requests must be combined. This is done simply by discarding requests
 * at the head of the queue until either only one requests is left (in which case
 * we use a NULL second context) or the first two requests have unique IDs.
 *
 * By always executing the first two requests in the queue the driver ensures
 * that the GPU is kept as busy as possible. In the case where a single context
 * completes but a second context is still executing, the request for this second
 * context will be at the head of the queue when we remove the first one. This
 * request will then be resubmitted along with a new request for a different context,
 * which will cause the hardware to continue executing the second request and queue
 * the new request (the GPU detects the condition of a context getting preempted
 * with the same context and optimizes the context switch flow by not doing
 * preemption, but just sampling the new tail pointer).
 *
 */

#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include "intel_mocs.h"

#define GEN9_LR_CONTEXT_RENDER_SIZE (22 * PAGE_SIZE)
#define GEN8_LR_CONTEXT_RENDER_SIZE (20 * PAGE_SIZE)
#define GEN8_LR_CONTEXT_OTHER_SIZE (2 * PAGE_SIZE)

#define RING_EXECLIST_QFULL             (1 << 0x2)
#define RING_EXECLIST1_VALID            (1 << 0x3)
#define RING_EXECLIST0_VALID            (1 << 0x4)
#define RING_EXECLIST_ACTIVE_STATUS     (3 << 0xE)
#define RING_EXECLIST1_ACTIVE           (1 << 0x11)
#define RING_EXECLIST0_ACTIVE           (1 << 0x12)

#define GEN8_CTX_STATUS_IDLE_ACTIVE     (1 << 0)
#define GEN8_CTX_STATUS_PREEMPTED       (1 << 1)
#define GEN8_CTX_STATUS_ELEMENT_SWITCH  (1 << 2)
#define GEN8_CTX_STATUS_ACTIVE_IDLE     (1 << 3)
#define GEN8_CTX_STATUS_COMPLETE        (1 << 4)
#define GEN8_CTX_STATUS_LITE_RESTORE    (1 << 15)

#define CTX_LRI_HEADER_0                0x01
#define CTX_CONTEXT_CONTROL             0x02
#define CTX_RING_HEAD                   0x04
#define CTX_RING_TAIL                   0x06
#define CTX_RING_BUFFER_START           0x08
#define CTX_RING_BUFFER_CONTROL         0x0a
#define CTX_BB_HEAD_U                   0x0c
#define CTX_BB_HEAD_L                   0x0e
#define CTX_BB_STATE                    0x10
#define CTX_SECOND_BB_HEAD_U            0x12
#define CTX_SECOND_BB_HEAD_L            0x14
#define CTX_SECOND_BB_STATE             0x16
#define CTX_BB_PER_CTX_PTR              0x18
#define CTX_RCS_INDIRECT_CTX            0x1a
#define CTX_RCS_INDIRECT_CTX_OFFSET     0x1c
#define CTX_LRI_HEADER_1                0x21
#define CTX_CTX_TIMESTAMP               0x22
#define CTX_PDP3_UDW                    0x24
#define CTX_PDP3_LDW                    0x26
#define CTX_PDP2_UDW                    0x28
#define CTX_PDP2_LDW                    0x2a
#define CTX_PDP1_UDW                    0x2c
#define CTX_PDP1_LDW                    0x2e
#define CTX_PDP0_UDW                    0x30
#define CTX_PDP0_LDW                    0x32
#define CTX_LRI_HEADER_2                0x41
#define CTX_R_PWR_CLK_STATE             0x42
#define CTX_GPGPU_CSR_BASE_ADDRESS      0x44

#define GEN8_CTX_VALID (1<<0)
#define GEN8_CTX_FORCE_PD_RESTORE (1<<1)
#define GEN8_CTX_FORCE_RESTORE (1<<2)
#define GEN8_CTX_L3LLC_COHERENT (1<<5)
#define GEN8_CTX_PRIVILEGE (1<<8)

#define ASSIGN_CTX_PDP(ppgtt, reg_state, n) { \
        const u64 _addr = i915_page_dir_dma_addr((ppgtt), (n)); \
        reg_state[CTX_PDP ## n ## _UDW+1] = upper_32_bits(_addr); \
        reg_state[CTX_PDP ## n ## _LDW+1] = lower_32_bits(_addr); \
}

#define ASSIGN_CTX_PML4(ppgtt, reg_state) { \
        reg_state[CTX_PDP0_UDW + 1] = upper_32_bits(px_dma(&ppgtt->pml4)); \
        reg_state[CTX_PDP0_LDW + 1] = lower_32_bits(px_dma(&ppgtt->pml4)); \
}

enum {
        ADVANCED_CONTEXT = 0,
        LEGACY_32B_CONTEXT,
        ADVANCED_AD_CONTEXT,
        LEGACY_64B_CONTEXT
};
#define GEN8_CTX_ADDRESSING_MODE_SHIFT 3
#define GEN8_CTX_ADDRESSING_MODE(dev)  (USES_FULL_48BIT_PPGTT(dev) ?\
                LEGACY_64B_CONTEXT :\
                LEGACY_32B_CONTEXT)
enum {
        FAULT_AND_HANG = 0,
        FAULT_AND_HALT, /* Debug only */
        FAULT_AND_STREAM,
        FAULT_AND_CONTINUE /* Unsupported */
};
#define GEN8_CTX_ID_SHIFT 32
#define CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT  0x17

static int intel_lr_context_pin(struct drm_i915_gem_request *rq);

/**
 * intel_sanitize_enable_execlists() - sanitize i915.enable_execlists
 * @dev: DRM device.
 * @enable_execlists: value of i915.enable_execlists module parameter.
 *
 * Only certain platforms support Execlists (the prerequisites being
 * support for Logical Ring Contexts and Aliasing PPGTT or better).
 *
 * Return: 1 if Execlists is supported and has to be enabled.
 */
int intel_sanitize_enable_execlists(struct drm_device *dev, int enable_execlists)
{
        WARN_ON(i915.enable_ppgtt == -1);

        /* On platforms with execlist available, vGPU will only
         * support execlist mode, no ring buffer mode.
         */
        if (HAS_LOGICAL_RING_CONTEXTS(dev) && intel_vgpu_active(dev))
                return 1;

        if (INTEL_INFO(dev)->gen >= 9)
                return 1;

        if (enable_execlists == 0)
                return 0;

        if (HAS_LOGICAL_RING_CONTEXTS(dev) && USES_PPGTT(dev) &&
            i915.use_mmio_flip >= 0)
                return 1;

        return 0;
}

/**
 * intel_execlists_ctx_id() - get the Execlists Context ID
 * @ctx_obj: Logical Ring Context backing object.
 *
 * Do not confuse with ctx->id! Unfortunately we have a name overload
 * here: the old context ID we pass to userspace as a handler so that
 * they can refer to a context, and the new context ID we pass to the
 * ELSP so that the GPU can inform us of the context status via
 * interrupts.
 *
 * Return: 20-bits globally unique context ID.
 */
u32 intel_execlists_ctx_id(struct drm_i915_gem_object *ctx_obj)
{
        u32 lrca = i915_gem_obj_ggtt_offset(ctx_obj) +
                        LRC_PPHWSP_PN * PAGE_SIZE;

        /* LRCA is required to be 4K aligned so the more significant 20 bits
         * are globally unique */
        return lrca >> 12;
}

uint64_t intel_lr_context_descriptor(struct intel_context *ctx,
                                     struct intel_engine_cs *ring)
{
        struct drm_device *dev = ring->dev;
        struct drm_i915_gem_object *ctx_obj = ctx->engine[ring->id].state;
        uint64_t desc;
        uint64_t lrca = i915_gem_obj_ggtt_offset(ctx_obj) +
                        LRC_PPHWSP_PN * PAGE_SIZE;

        WARN_ON(lrca & 0xFFFFFFFF00000FFFULL);

        desc = GEN8_CTX_VALID;
        desc |= GEN8_CTX_ADDRESSING_MODE(dev) << GEN8_CTX_ADDRESSING_MODE_SHIFT;
        if (IS_GEN8(ctx_obj->base.dev))
                desc |= GEN8_CTX_L3LLC_COHERENT;
        desc |= GEN8_CTX_PRIVILEGE;
        desc |= lrca;
        desc |= (u64)intel_execlists_ctx_id(ctx_obj) << GEN8_CTX_ID_SHIFT;

        /* TODO: WaDisableLiteRestore when we start using semaphore
         * signalling between Command Streamers */
        /* desc |= GEN8_CTX_FORCE_RESTORE; */

        /* WaEnableForceRestoreInCtxtDescForVCS:skl */
        if (IS_GEN9(dev) &&
            INTEL_REVID(dev) <= SKL_REVID_B0 &&
            (ring->id == BCS || ring->id == VCS ||
            ring->id == VECS || ring->id == VCS2))
                desc |= GEN8_CTX_FORCE_RESTORE;

        return desc;
}

static void execlists_elsp_write(struct drm_i915_gem_request *rq0,
                                 struct drm_i915_gem_request *rq1)
{

        struct intel_engine_cs *ring = rq0->ring;
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        uint64_t desc[2];

        if (rq1) {
                desc[1] = intel_lr_context_descriptor(rq1->ctx, rq1->ring);
                rq1->elsp_submitted++;
        } else {
                desc[1] = 0;
        }

        desc[0] = intel_lr_context_descriptor(rq0->ctx, rq0->ring);
        rq0->elsp_submitted++;

        /* You must always write both descriptors in the order below. */
        spin_lock(&dev_priv->uncore.lock);
        intel_uncore_forcewake_get__locked(dev_priv, FORCEWAKE_ALL);
        I915_WRITE_FW(RING_ELSP(ring), upper_32_bits(desc[1]));
        I915_WRITE_FW(RING_ELSP(ring), lower_32_bits(desc[1]));

        I915_WRITE_FW(RING_ELSP(ring), upper_32_bits(desc[0]));
        /* The context is automatically loaded after the following */
        I915_WRITE_FW(RING_ELSP(ring), lower_32_bits(desc[0]));

        /* ELSP is a wo register, use another nearby reg for posting */
        POSTING_READ_FW(RING_EXECLIST_STATUS(ring));
        intel_uncore_forcewake_put__locked(dev_priv, FORCEWAKE_ALL);
        spin_unlock(&dev_priv->uncore.lock);
}

static int execlists_update_context(struct drm_i915_gem_request *rq)
{
        struct intel_engine_cs *ring = rq->ring;
        struct i915_hw_ppgtt *ppgtt = rq->ctx->ppgtt;
        struct drm_i915_gem_object *ctx_obj = rq->ctx->engine[ring->id].state;
        struct drm_i915_gem_object *rb_obj = rq->ringbuf->obj;
        struct page *page;
        uint32_t *reg_state;

        BUG_ON(!ctx_obj);
        WARN_ON(!i915_gem_obj_is_pinned(ctx_obj));
        WARN_ON(!i915_gem_obj_is_pinned(rb_obj));

        page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
        reg_state = kmap_atomic(page);

        reg_state[CTX_RING_TAIL+1] = rq->tail;
        reg_state[CTX_RING_BUFFER_START+1] = i915_gem_obj_ggtt_offset(rb_obj);

        if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
                /* True 32b PPGTT with dynamic page allocation: update PDP
                 * registers and point the unallocated PDPs to scratch page.
                 * PML4 is allocated during ppgtt init, so this is not needed
                 * in 48-bit mode.
                 */
                ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
                ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
                ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
                ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
        }

        kunmap_atomic(reg_state);

        return 0;
}

static void execlists_submit_requests(struct drm_i915_gem_request *rq0,
                                      struct drm_i915_gem_request *rq1)
{
        execlists_update_context(rq0);

        if (rq1)
                execlists_update_context(rq1);

        execlists_elsp_write(rq0, rq1);
}

static void execlists_context_unqueue(struct intel_engine_cs *ring)
{
        struct drm_i915_gem_request *req0 = NULL, *req1 = NULL;
        struct drm_i915_gem_request *cursor = NULL, *tmp = NULL;

        assert_spin_locked(&ring->execlist_lock);

        /*
         * If irqs are not active generate a warning as batches that finish
         * without the irqs may get lost and a GPU Hang may occur.
         */
        WARN_ON(!intel_irqs_enabled(ring->dev->dev_private));

        if (list_empty(&ring->execlist_queue))
                return;

        /* Try to read in pairs */
        list_for_each_entry_safe(cursor, tmp, &ring->execlist_queue,
                                 execlist_link) {
                if (!req0) {
                        req0 = cursor;
                } else if (req0->ctx == cursor->ctx) {
                        /* Same ctx: ignore first request, as second request
                         * will update tail past first request's workload */
                        cursor->elsp_submitted = req0->elsp_submitted;
                        list_del(&req0->execlist_link);
                        list_add_tail(&req0->execlist_link,
                                &ring->execlist_retired_req_list);
                        req0 = cursor;
                } else {
                        req1 = cursor;
                        break;
                }
        }

        if (IS_GEN8(ring->dev) || IS_GEN9(ring->dev)) {
                /*
                 * WaIdleLiteRestore: make sure we never cause a lite
                 * restore with HEAD==TAIL
                 */
                if (req0->elsp_submitted) {
                        /*
                         * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL
                         * as we resubmit the request. See gen8_emit_request()
                         * for where we prepare the padding after the end of the
                         * request.
                         */
                        struct intel_ringbuffer *ringbuf;

                        ringbuf = req0->ctx->engine[ring->id].ringbuf;
                        req0->tail += 8;
                        req0->tail &= ringbuf->size - 1;
                }
        }

        WARN_ON(req1 && req1->elsp_submitted);

        execlists_submit_requests(req0, req1);
}

static bool execlists_check_remove_request(struct intel_engine_cs *ring,
                                           u32 request_id)
{
        struct drm_i915_gem_request *head_req;

        assert_spin_locked(&ring->execlist_lock);

        head_req = list_first_entry_or_null(&ring->execlist_queue,
                                            struct drm_i915_gem_request,
                                            execlist_link);

        if (head_req != NULL) {
                struct drm_i915_gem_object *ctx_obj =
                                head_req->ctx->engine[ring->id].state;
                if (intel_execlists_ctx_id(ctx_obj) == request_id) {
                        WARN(head_req->elsp_submitted == 0,
                             "Never submitted head request\n");

                        if (--head_req->elsp_submitted <= 0) {
                                list_del(&head_req->execlist_link);
                                list_add_tail(&head_req->execlist_link,
                                        &ring->execlist_retired_req_list);
                                return true;
                        }
                }
        }

        return false;
}

/**
 * intel_lrc_irq_handler() - handle Context Switch interrupts
 * @ring: Engine Command Streamer to handle.
 *
 * Check the unread Context Status Buffers and manage the submission of new
 * contexts to the ELSP accordingly.
 */
void intel_lrc_irq_handler(struct intel_engine_cs *ring)
{
        struct drm_i915_private *dev_priv = ring->dev->dev_private;
        u32 status_pointer;
        u8 read_pointer;
        u8 write_pointer;
        u32 status;
        u32 status_id;
        u32 submit_contexts = 0;

        status_pointer = I915_READ(RING_CONTEXT_STATUS_PTR(ring));

        read_pointer = ring->next_context_status_buffer;
        write_pointer = status_pointer & 0x07;
        if (read_pointer > write_pointer)
                write_pointer += 6;

        spin_lock(&ring->execlist_lock);

        while (read_pointer < write_pointer) {
                read_pointer++;
                status = I915_READ(RING_CONTEXT_STATUS_BUF(ring) +
                                (read_pointer % 6) * 8);
                status_id = I915_READ(RING_CONTEXT_STATUS_BUF(ring) +
                                (read_pointer % 6) * 8 + 4);

                if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
                        continue;

                if (status & GEN8_CTX_STATUS_PREEMPTED) {
                        if (status & GEN8_CTX_STATUS_LITE_RESTORE) {
                                if (execlists_check_remove_request(ring, status_id))
                                        WARN(1, "Lite Restored request removed from queue\n");
                        } else
                                WARN(1, "Preemption without Lite Restore\n");
                }

                 if ((status & GEN8_CTX_STATUS_ACTIVE_IDLE) ||
                     (status & GEN8_CTX_STATUS_ELEMENT_SWITCH)) {
                        if (execlists_check_remove_request(ring, status_id))
                                submit_contexts++;
                }
        }

        if (submit_contexts != 0)
                execlists_context_unqueue(ring);

        spin_unlock(&ring->execlist_lock);

        WARN(submit_contexts > 2, "More than two context complete events?\n");
        ring->next_context_status_buffer = write_pointer % 6;

        I915_WRITE(RING_CONTEXT_STATUS_PTR(ring),
                   _MASKED_FIELD(0x07 << 8, ((u32)ring->next_context_status_buffer & 0x07) << 8));
}

static int execlists_context_queue(struct drm_i915_gem_request *request)
{
        struct intel_engine_cs *ring = request->ring;
        struct drm_i915_gem_request *cursor;
        int num_elements = 0;

        if (request->ctx != ring->default_context)
                intel_lr_context_pin(request);

        i915_gem_request_reference(request);

        spin_lock_irq(&ring->execlist_lock);

        list_for_each_entry(cursor, &ring->execlist_queue, execlist_link)
                if (++num_elements > 2)
                        break;

        if (num_elements > 2) {
                struct drm_i915_gem_request *tail_req;

                tail_req = list_last_entry(&ring->execlist_queue,
                                           struct drm_i915_gem_request,
                                           execlist_link);

                if (request->ctx == tail_req->ctx) {
                        WARN(tail_req->elsp_submitted != 0,
                                "More than 2 already-submitted reqs queued\n");
                        list_del(&tail_req->execlist_link);
                        list_add_tail(&tail_req->execlist_link,
                                &ring->execlist_retired_req_list);
                }
        }

        list_add_tail(&request->execlist_link, &ring->execlist_queue);
        if (num_elements == 0)
                execlists_context_unqueue(ring);

        spin_unlock_irq(&ring->execlist_lock);

        return 0;
}

static int logical_ring_invalidate_all_caches(struct drm_i915_gem_request *req)
{
        struct intel_engine_cs *ring = req->ring;
        uint32_t flush_domains;
        int ret;

        flush_domains = 0;
        if (ring->gpu_caches_dirty)
                flush_domains = I915_GEM_GPU_DOMAINS;

        ret = ring->emit_flush(req, I915_GEM_GPU_DOMAINS, flush_domains);
        if (ret)
                return ret;

        ring->gpu_caches_dirty = false;
        return 0;
}

static int execlists_move_to_gpu(struct drm_i915_gem_request *req,
                                 struct list_head *vmas)
{
        const unsigned other_rings = ~intel_ring_flag(req->ring);
        struct i915_vma *vma;
        uint32_t flush_domains = 0;
        bool flush_chipset = false;
        int ret;

        list_for_each_entry(vma, vmas, exec_list) {
                struct drm_i915_gem_object *obj = vma->obj;

                if (obj->active & other_rings) {
                        ret = i915_gem_object_sync(obj, req->ring, &req);
                        if (ret)
                                return ret;
                }

                if (obj->base.write_domain & I915_GEM_DOMAIN_CPU)
                        flush_chipset |= i915_gem_clflush_object(obj, false);

                flush_domains |= obj->base.write_domain;
        }

        if (flush_domains & I915_GEM_DOMAIN_GTT)
                wmb();

        /* Unconditionally invalidate gpu caches and ensure that we do flush
         * any residual writes from the previous batch.
         */
        return logical_ring_invalidate_all_caches(req);
}

int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request)
{
        int ret;

        request->ringbuf = request->ctx->engine[request->ring->id].ringbuf;

        if (request->ctx != request->ring->default_context) {
                ret = intel_lr_context_pin(request);
                if (ret)
                        return ret;
        }

        return 0;
}

static int logical_ring_wait_for_space(struct drm_i915_gem_request *req,
                                       int bytes)
{
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        struct intel_engine_cs *ring = req->ring;
        struct drm_i915_gem_request *target;
        unsigned space;
        int ret;

        if (intel_ring_space(ringbuf) >= bytes)
                return 0;

        /* The whole point of reserving space is to not wait! */
        WARN_ON(ringbuf->reserved_in_use);

        list_for_each_entry(target, &ring->request_list, list) {
                /*
                 * The request queue is per-engine, so can contain requests
                 * from multiple ringbuffers. Here, we must ignore any that
                 * aren't from the ringbuffer we're considering.
                 */
                if (target->ringbuf != ringbuf)
                        continue;

                /* Would completion of this request free enough space? */
                space = __intel_ring_space(target->postfix, ringbuf->tail,
                                           ringbuf->size);
                if (space >= bytes)
                        break;
        }

        if (WARN_ON(&target->list == &ring->request_list))
                return -ENOSPC;

        ret = i915_wait_request(target);
        if (ret)
                return ret;

        ringbuf->space = space;
        return 0;
}

/*
 * intel_logical_ring_advance_and_submit() - advance the tail and submit the workload
 * @request: Request to advance the logical ringbuffer of.
 *
 * The tail is updated in our logical ringbuffer struct, not in the actual context. What
 * really happens during submission is that the context and current tail will be placed
 * on a queue waiting for the ELSP to be ready to accept a new context submission. At that
 * point, the tail *inside* the context is updated and the ELSP written to.
 */
static void
intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request)
{
        struct intel_engine_cs *ring = request->ring;
        struct drm_i915_private *dev_priv = request->i915;

        intel_logical_ring_advance(request->ringbuf);

        request->tail = request->ringbuf->tail;

        if (intel_ring_stopped(ring))
                return;

        if (dev_priv->guc.execbuf_client)
                i915_guc_submit(dev_priv->guc.execbuf_client, request);
        else
                execlists_context_queue(request);
}

static void __wrap_ring_buffer(struct intel_ringbuffer *ringbuf)
{
        uint32_t __iomem *virt;
        int rem = ringbuf->size - ringbuf->tail;

        virt = ringbuf->virtual_start + ringbuf->tail;
        rem /= 4;
        while (rem--)
                iowrite32(MI_NOOP, virt++);

        ringbuf->tail = 0;
        intel_ring_update_space(ringbuf);
}

static int logical_ring_prepare(struct drm_i915_gem_request *req, int bytes)
{
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        int remain_usable = ringbuf->effective_size - ringbuf->tail;
        int remain_actual = ringbuf->size - ringbuf->tail;
        int ret, total_bytes, wait_bytes = 0;
        bool need_wrap = false;

        if (ringbuf->reserved_in_use)
                total_bytes = bytes;
        else
                total_bytes = bytes + ringbuf->reserved_size;

        if (unlikely(bytes > remain_usable)) {
                /*
                 * Not enough space for the basic request. So need to flush
                 * out the remainder and then wait for base + reserved.
                 */
                wait_bytes = remain_actual + total_bytes;
                need_wrap = true;
        } else {
                if (unlikely(total_bytes > remain_usable)) {
                        /*
                         * The base request will fit but the reserved space
                         * falls off the end. So only need to to wait for the
                         * reserved size after flushing out the remainder.
                         */
                        wait_bytes = remain_actual + ringbuf->reserved_size;
                        need_wrap = true;
                } else if (total_bytes > ringbuf->space) {
                        /* No wrapping required, just waiting. */
                        wait_bytes = total_bytes;
                }
        }

        if (wait_bytes) {
                ret = logical_ring_wait_for_space(req, wait_bytes);
                if (unlikely(ret))
                        return ret;

                if (need_wrap)
                        __wrap_ring_buffer(ringbuf);
        }

        return 0;
}

/**
 * intel_logical_ring_begin() - prepare the logical ringbuffer to accept some commands
 *
 * @request: The request to start some new work for
 * @ctx: Logical ring context whose ringbuffer is being prepared.
 * @num_dwords: number of DWORDs that we plan to write to the ringbuffer.
 *
 * The ringbuffer might not be ready to accept the commands right away (maybe it needs to
 * be wrapped, or wait a bit for the tail to be updated). This function takes care of that
 * and also preallocates a request (every workload submission is still mediated through
 * requests, same as it did with legacy ringbuffer submission).
 *
 * Return: non-zero if the ringbuffer is not ready to be written to.
 */
int intel_logical_ring_begin(struct drm_i915_gem_request *req, int num_dwords)
{
        struct drm_i915_private *dev_priv;
        int ret;

        WARN_ON(req == NULL);
        dev_priv = req->ring->dev->dev_private;

        ret = i915_gem_check_wedge(&dev_priv->gpu_error,
                                   dev_priv->mm.interruptible);
        if (ret)
                return ret;

        ret = logical_ring_prepare(req, num_dwords * sizeof(uint32_t));
        if (ret)
                return ret;

        req->ringbuf->space -= num_dwords * sizeof(uint32_t);
        return 0;
}

int intel_logical_ring_reserve_space(struct drm_i915_gem_request *request)
{
        /*
         * The first call merely notes the reserve request and is common for
         * all back ends. The subsequent localised _begin() call actually
         * ensures that the reservation is available. Without the begin, if
         * the request creator immediately submitted the request without
         * adding any commands to it then there might not actually be
         * sufficient room for the submission commands.
         */
        intel_ring_reserved_space_reserve(request->ringbuf, MIN_SPACE_FOR_ADD_REQUEST);

        return intel_logical_ring_begin(request, 0);
}

/**
 * execlists_submission() - submit a batchbuffer for execution, Execlists style
 * @dev: DRM device.
 * @file: DRM file.
 * @ring: Engine Command Streamer to submit to.
 * @ctx: Context to employ for this submission.
 * @args: execbuffer call arguments.
 * @vmas: list of vmas.
 * @batch_obj: the batchbuffer to submit.
 * @exec_start: batchbuffer start virtual address pointer.
 * @dispatch_flags: translated execbuffer call flags.
 *
 * This is the evil twin version of i915_gem_ringbuffer_submission. It abstracts
 * away the submission details of the execbuffer ioctl call.
 *
 * Return: non-zero if the submission fails.
 */
int intel_execlists_submission(struct i915_execbuffer_params *params,
                               struct drm_i915_gem_execbuffer2 *args,
                               struct list_head *vmas)
{
        struct drm_device       *dev = params->dev;
        struct intel_engine_cs  *ring = params->ring;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_ringbuffer *ringbuf = params->ctx->engine[ring->id].ringbuf;
        u64 exec_start;
        int instp_mode;
        u32 instp_mask;
        int ret;

        instp_mode = args->flags & I915_EXEC_CONSTANTS_MASK;
        instp_mask = I915_EXEC_CONSTANTS_MASK;
        switch (instp_mode) {
        case I915_EXEC_CONSTANTS_REL_GENERAL:
        case I915_EXEC_CONSTANTS_ABSOLUTE:
        case I915_EXEC_CONSTANTS_REL_SURFACE:
                if (instp_mode != 0 && ring != &dev_priv->ring[RCS]) {
                        DRM_DEBUG("non-0 rel constants mode on non-RCS\n");
                        return -EINVAL;
                }

                if (instp_mode != dev_priv->relative_constants_mode) {
                        if (instp_mode == I915_EXEC_CONSTANTS_REL_SURFACE) {
                                DRM_DEBUG("rel surface constants mode invalid on gen5+\n");
                                return -EINVAL;
                        }

                        /* The HW changed the meaning on this bit on gen6 */
                        instp_mask &= ~I915_EXEC_CONSTANTS_REL_SURFACE;
                }
                break;
        default:
                DRM_DEBUG("execbuf with unknown constants: %d\n", instp_mode);
                return -EINVAL;
        }

        if (args->num_cliprects != 0) {
                DRM_DEBUG("clip rectangles are only valid on pre-gen5\n");
                return -EINVAL;
        } else {
                if (args->DR4 == 0xffffffff) {
                        DRM_DEBUG("UXA submitting garbage DR4, fixing up\n");
                        args->DR4 = 0;
                }

                if (args->DR1 || args->DR4 || args->cliprects_ptr) {
                        DRM_DEBUG("0 cliprects but dirt in cliprects fields\n");
                        return -EINVAL;
                }
        }

        if (args->flags & I915_EXEC_GEN7_SOL_RESET) {
                DRM_DEBUG("sol reset is gen7 only\n");
                return -EINVAL;
        }

        ret = execlists_move_to_gpu(params->request, vmas);
        if (ret)
                return ret;

        if (ring == &dev_priv->ring[RCS] &&
            instp_mode != dev_priv->relative_constants_mode) {
                ret = intel_logical_ring_begin(params->request, 4);
                if (ret)
                        return ret;

                intel_logical_ring_emit(ringbuf, MI_NOOP);
                intel_logical_ring_emit(ringbuf, MI_LOAD_REGISTER_IMM(1));
                intel_logical_ring_emit(ringbuf, INSTPM);
                intel_logical_ring_emit(ringbuf, instp_mask << 16 | instp_mode);
                intel_logical_ring_advance(ringbuf);

                dev_priv->relative_constants_mode = instp_mode;
        }

        exec_start = params->batch_obj_vm_offset +
                     args->batch_start_offset;

        ret = ring->emit_bb_start(params->request, exec_start, params->dispatch_flags);
        if (ret)
                return ret;

        trace_i915_gem_ring_dispatch(params->request, params->dispatch_flags);

        i915_gem_execbuffer_move_to_active(vmas, params->request);
        i915_gem_execbuffer_retire_commands(params);

        return 0;
}

void intel_execlists_retire_requests(struct intel_engine_cs *ring)
{
        struct drm_i915_gem_request *req, *tmp;
        struct list_head retired_list;

        WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
        if (list_empty(&ring->execlist_retired_req_list))
                return;

        INIT_LIST_HEAD(&retired_list);
        spin_lock_irq(&ring->execlist_lock);
        list_replace_init(&ring->execlist_retired_req_list, &retired_list);
        spin_unlock_irq(&ring->execlist_lock);

        list_for_each_entry_safe(req, tmp, &retired_list, execlist_link) {
                struct intel_context *ctx = req->ctx;
                struct drm_i915_gem_object *ctx_obj =
                                ctx->engine[ring->id].state;

                if (ctx_obj && (ctx != ring->default_context))
                        intel_lr_context_unpin(req);
                list_del(&req->execlist_link);
                i915_gem_request_unreference(req);
        }
}

void intel_logical_ring_stop(struct intel_engine_cs *ring)
{
        struct drm_i915_private *dev_priv = ring->dev->dev_private;
        int ret;

        if (!intel_ring_initialized(ring))
                return;

        ret = intel_ring_idle(ring);
        if (ret && !i915_reset_in_progress(&to_i915(ring->dev)->gpu_error))
                DRM_ERROR("failed to quiesce %s whilst cleaning up: %d\n",
                          ring->name, ret);

        /* TODO: Is this correct with Execlists enabled? */
        I915_WRITE_MODE(ring, _MASKED_BIT_ENABLE(STOP_RING));
        if (wait_for_atomic((I915_READ_MODE(ring) & MODE_IDLE) != 0, 1000)) {
                DRM_ERROR("%s :timed out trying to stop ring\n", ring->name);
                return;
        }
        I915_WRITE_MODE(ring, _MASKED_BIT_DISABLE(STOP_RING));
}

int logical_ring_flush_all_caches(struct drm_i915_gem_request *req)
{
        struct intel_engine_cs *ring = req->ring;
        int ret;

        if (!ring->gpu_caches_dirty)
                return 0;

        ret = ring->emit_flush(req, 0, I915_GEM_GPU_DOMAINS);
        if (ret)
                return ret;

        ring->gpu_caches_dirty = false;
        return 0;
}

static int intel_lr_context_pin(struct drm_i915_gem_request *rq)
{
        struct drm_i915_private *dev_priv = rq->i915;
        struct intel_engine_cs *ring = rq->ring;
        struct drm_i915_gem_object *ctx_obj = rq->ctx->engine[ring->id].state;
        struct intel_ringbuffer *ringbuf = rq->ringbuf;
        int ret = 0;

        WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
        if (rq->ctx->engine[ring->id].pin_count++ == 0) {
                ret = i915_gem_obj_ggtt_pin(ctx_obj, GEN8_LR_CONTEXT_ALIGN,
                                PIN_OFFSET_BIAS | GUC_WOPCM_TOP);
                if (ret)
                        goto reset_pin_count;

                ret = intel_pin_and_map_ringbuffer_obj(ring->dev, ringbuf);
                if (ret)
                        goto unpin_ctx_obj;

                ctx_obj->dirty = true;

                /* Invalidate GuC TLB. */
                if (i915.enable_guc_submission)
                        I915_WRITE(GEN8_GTCR, GEN8_GTCR_INVALIDATE);
        }

        return ret;

unpin_ctx_obj:
        i915_gem_object_ggtt_unpin(ctx_obj);
reset_pin_count:
        rq->ctx->engine[ring->id].pin_count = 0;

        return ret;
}

void intel_lr_context_unpin(struct drm_i915_gem_request *rq)
{
        struct intel_engine_cs *ring = rq->ring;
        struct drm_i915_gem_object *ctx_obj = rq->ctx->engine[ring->id].state;
        struct intel_ringbuffer *ringbuf = rq->ringbuf;

        if (ctx_obj) {
                WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
                if (--rq->ctx->engine[ring->id].pin_count == 0) {
                        intel_unpin_ringbuffer_obj(ringbuf);
                        i915_gem_object_ggtt_unpin(ctx_obj);
                }
        }
}

static int intel_logical_ring_workarounds_emit(struct drm_i915_gem_request *req)
{
        int ret, i;
        struct intel_engine_cs *ring = req->ring;
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct i915_workarounds *w = &dev_priv->workarounds;

        if (WARN_ON_ONCE(w->count == 0))
                return 0;

        ring->gpu_caches_dirty = true;
        ret = logical_ring_flush_all_caches(req);
        if (ret)
                return ret;

        ret = intel_logical_ring_begin(req, w->count * 2 + 2);
        if (ret)
                return ret;

        intel_logical_ring_emit(ringbuf, MI_LOAD_REGISTER_IMM(w->count));
        for (i = 0; i < w->count; i++) {
                intel_logical_ring_emit(ringbuf, w->reg[i].addr);
                intel_logical_ring_emit(ringbuf, w->reg[i].value);
        }
        intel_logical_ring_emit(ringbuf, MI_NOOP);

        intel_logical_ring_advance(ringbuf);

        ring->gpu_caches_dirty = true;
        ret = logical_ring_flush_all_caches(req);
        if (ret)
                return ret;

        return 0;
}

#define wa_ctx_emit(batch, index, cmd)                                  \
        do {                                                            \
                int __index = (index)++;                                \
                if (WARN_ON(__index >= (PAGE_SIZE / sizeof(uint32_t)))) { \
                        return -ENOSPC;                                 \
                }                                                       \
                batch[__index] = (cmd);                                 \
        } while (0)


/*
 * In this WA we need to set GEN8_L3SQCREG4[21:21] and reset it after
 * PIPE_CONTROL instruction. This is required for the flush to happen correctly
 * but there is a slight complication as this is applied in WA batch where the
 * values are only initialized once so we cannot take register value at the
 * beginning and reuse it further; hence we save its value to memory, upload a
 * constant value with bit21 set and then we restore it back with the saved value.
 * To simplify the WA, a constant value is formed by using the default value
 * of this register. This shouldn't be a problem because we are only modifying
 * it for a short period and this batch in non-premptible. We can ofcourse
 * use additional instructions that read the actual value of the register
 * at that time and set our bit of interest but it makes the WA complicated.
 *
 * This WA is also required for Gen9 so extracting as a function avoids
 * code duplication.
 */
static inline int gen8_emit_flush_coherentl3_wa(struct intel_engine_cs *ring,
                                                uint32_t *const batch,
                                                uint32_t index)
{
        uint32_t l3sqc4_flush = (0x40400000 | GEN8_LQSC_FLUSH_COHERENT_LINES);

        /*
         * WaDisableLSQCROPERFforOCL:skl
         * This WA is implemented in skl_init_clock_gating() but since
         * this batch updates GEN8_L3SQCREG4 with default value we need to
         * set this bit here to retain the WA during flush.
         */
        if (IS_SKYLAKE(ring->dev) && INTEL_REVID(ring->dev) <= SKL_REVID_E0)
                l3sqc4_flush |= GEN8_LQSC_RO_PERF_DIS;

        wa_ctx_emit(batch, index, (MI_STORE_REGISTER_MEM_GEN8 |
                                   MI_SRM_LRM_GLOBAL_GTT));
        wa_ctx_emit(batch, index, GEN8_L3SQCREG4);
        wa_ctx_emit(batch, index, ring->scratch.gtt_offset + 256);
        wa_ctx_emit(batch, index, 0);

        wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(1));
        wa_ctx_emit(batch, index, GEN8_L3SQCREG4);
        wa_ctx_emit(batch, index, l3sqc4_flush);

        wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
        wa_ctx_emit(batch, index, (PIPE_CONTROL_CS_STALL |
                                   PIPE_CONTROL_DC_FLUSH_ENABLE));
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);

        wa_ctx_emit(batch, index, (MI_LOAD_REGISTER_MEM_GEN8 |
                                   MI_SRM_LRM_GLOBAL_GTT));
        wa_ctx_emit(batch, index, GEN8_L3SQCREG4);
        wa_ctx_emit(batch, index, ring->scratch.gtt_offset + 256);
        wa_ctx_emit(batch, index, 0);

        return index;
}

static inline uint32_t wa_ctx_start(struct i915_wa_ctx_bb *wa_ctx,
                                    uint32_t offset,
                                    uint32_t start_alignment)
{
        return wa_ctx->offset = ALIGN(offset, start_alignment);
}

static inline int wa_ctx_end(struct i915_wa_ctx_bb *wa_ctx,
                             uint32_t offset,
                             uint32_t size_alignment)
{
        wa_ctx->size = offset - wa_ctx->offset;

        WARN(wa_ctx->size % size_alignment,
             "wa_ctx_bb failed sanity checks: size %d is not aligned to %d\n",
             wa_ctx->size, size_alignment);
        return 0;
}

/**
 * gen8_init_indirectctx_bb() - initialize indirect ctx batch with WA
 *
 * @ring: only applicable for RCS
 * @wa_ctx: structure representing wa_ctx
 *  offset: specifies start of the batch, should be cache-aligned. This is updated
 *    with the offset value received as input.
 *  size: size of the batch in DWORDS but HW expects in terms of cachelines
 * @batch: page in which WA are loaded
 * @offset: This field specifies the start of the batch, it should be
 *  cache-aligned otherwise it is adjusted accordingly.
 *  Typically we only have one indirect_ctx and per_ctx batch buffer which are
 *  initialized at the beginning and shared across all contexts but this field
 *  helps us to have multiple batches at different offsets and select them based
 *  on a criteria. At the moment this batch always start at the beginning of the page
 *  and at this point we don't have multiple wa_ctx batch buffers.
 *
 *  The number of WA applied are not known at the beginning; we use this field
 *  to return the no of DWORDS written.
 *
 *  It is to be noted that this batch does not contain MI_BATCH_BUFFER_END
 *  so it adds NOOPs as padding to make it cacheline aligned.
 *  MI_BATCH_BUFFER_END will be added to perctx batch and both of them together
 *  makes a complete batch buffer.
 *
 * Return: non-zero if we exceed the PAGE_SIZE limit.
 */

static int gen8_init_indirectctx_bb(struct intel_engine_cs *ring,
                                    struct i915_wa_ctx_bb *wa_ctx,
                                    uint32_t *const batch,
                                    uint32_t *offset)
{
        uint32_t scratch_addr;
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaDisableCtxRestoreArbitration:bdw,chv */
        wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_DISABLE);

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:bdw */
        if (IS_BROADWELL(ring->dev)) {
                index = gen8_emit_flush_coherentl3_wa(ring, batch, index);
                if (index < 0)
                        return index;
        }

        /* WaClearSlmSpaceAtContextSwitch:bdw,chv */
        /* Actual scratch location is at 128 bytes offset */
        scratch_addr = ring->scratch.gtt_offset + 2*CACHELINE_BYTES;

        wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
        wa_ctx_emit(batch, index, (PIPE_CONTROL_FLUSH_L3 |
                                   PIPE_CONTROL_GLOBAL_GTT_IVB |
                                   PIPE_CONTROL_CS_STALL |
                                   PIPE_CONTROL_QW_WRITE));
        wa_ctx_emit(batch, index, scratch_addr);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);

        /* Pad to end of cacheline */
        while (index % CACHELINE_DWORDS)
                wa_ctx_emit(batch, index, MI_NOOP);

        /*
         * MI_BATCH_BUFFER_END is not required in Indirect ctx BB because
         * execution depends on the length specified in terms of cache lines
         * in the register CTX_RCS_INDIRECT_CTX
         */

        return wa_ctx_end(wa_ctx, *offset = index, CACHELINE_DWORDS);
}

/**
 * gen8_init_perctx_bb() - initialize per ctx batch with WA
 *
 * @ring: only applicable for RCS
 * @wa_ctx: structure representing wa_ctx
 *  offset: specifies start of the batch, should be cache-aligned.
 *  size: size of the batch in DWORDS but HW expects in terms of cachelines
 * @batch: page in which WA are loaded
 * @offset: This field specifies the start of this batch.
 *   This batch is started immediately after indirect_ctx batch. Since we ensure
 *   that indirect_ctx ends on a cacheline this batch is aligned automatically.
 *
 *   The number of DWORDS written are returned using this field.
 *
 *  This batch is terminated with MI_BATCH_BUFFER_END and so we need not add padding
 *  to align it with cacheline as padding after MI_BATCH_BUFFER_END is redundant.
 */
static int gen8_init_perctx_bb(struct intel_engine_cs *ring,
                               struct i915_wa_ctx_bb *wa_ctx,
                               uint32_t *const batch,
                               uint32_t *offset)
{
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaDisableCtxRestoreArbitration:bdw,chv */
        wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_ENABLE);

        wa_ctx_emit(batch, index, MI_BATCH_BUFFER_END);

        return wa_ctx_end(wa_ctx, *offset = index, 1);
}

static int gen9_init_indirectctx_bb(struct intel_engine_cs *ring,
                                    struct i915_wa_ctx_bb *wa_ctx,
                                    uint32_t *const batch,
                                    uint32_t *offset)
{
        int ret;
        struct drm_device *dev = ring->dev;
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaDisableCtxRestoreArbitration:skl,bxt */
        if ((IS_SKYLAKE(dev) && (INTEL_REVID(dev) <= SKL_REVID_D0)) ||
            (IS_BROXTON(dev) && (INTEL_REVID(dev) == BXT_REVID_A0)))
                wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_DISABLE);

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:skl,bxt */
        ret = gen8_emit_flush_coherentl3_wa(ring, batch, index);
        if (ret < 0)
                return ret;
        index = ret;

        /* Pad to end of cacheline */
        while (index % CACHELINE_DWORDS)
                wa_ctx_emit(batch, index, MI_NOOP);

        return wa_ctx_end(wa_ctx, *offset = index, CACHELINE_DWORDS);
}

static int gen9_init_perctx_bb(struct intel_engine_cs *ring,
                               struct i915_wa_ctx_bb *wa_ctx,
                               uint32_t *const batch,
                               uint32_t *offset)
{
        struct drm_device *dev = ring->dev;
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken:skl,bxt */
        if ((IS_SKYLAKE(dev) && (INTEL_REVID(dev) <= SKL_REVID_B0)) ||
            (IS_BROXTON(dev) && (INTEL_REVID(dev) == BXT_REVID_A0))) {
                wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(1));
                wa_ctx_emit(batch, index, GEN9_SLICE_COMMON_ECO_CHICKEN0);
                wa_ctx_emit(batch, index,
                            _MASKED_BIT_ENABLE(DISABLE_PIXEL_MASK_CAMMING));
                wa_ctx_emit(batch, index, MI_NOOP);
        }

        /* WaDisableCtxRestoreArbitration:skl,bxt */
        if ((IS_SKYLAKE(dev) && (INTEL_REVID(dev) <= SKL_REVID_D0)) ||
            (IS_BROXTON(dev) && (INTEL_REVID(dev) == BXT_REVID_A0)))
                wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_ENABLE);

        wa_ctx_emit(batch, index, MI_BATCH_BUFFER_END);

        return wa_ctx_end(wa_ctx, *offset = index, 1);
}

static int lrc_setup_wa_ctx_obj(struct intel_engine_cs *ring, u32 size)
{
        int ret;

        ring->wa_ctx.obj = i915_gem_alloc_object(ring->dev, PAGE_ALIGN(size));
        if (!ring->wa_ctx.obj) {
                DRM_DEBUG_DRIVER("alloc LRC WA ctx backing obj failed.\n");
                return -ENOMEM;
        }

        ret = i915_gem_obj_ggtt_pin(ring->wa_ctx.obj, PAGE_SIZE, 0);
        if (ret) {
                DRM_DEBUG_DRIVER("pin LRC WA ctx backing obj failed: %d\n",
                                 ret);
                drm_gem_object_unreference(&ring->wa_ctx.obj->base);
                return ret;
        }

        return 0;
}

static void lrc_destroy_wa_ctx_obj(struct intel_engine_cs *ring)
{
        if (ring->wa_ctx.obj) {
                i915_gem_object_ggtt_unpin(ring->wa_ctx.obj);
                drm_gem_object_unreference(&ring->wa_ctx.obj->base);
                ring->wa_ctx.obj = NULL;
        }
}

static int intel_init_workaround_bb(struct intel_engine_cs *ring)
{
        int ret;
        uint32_t *batch;
        uint32_t offset;
        struct page *page;
        struct i915_ctx_workarounds *wa_ctx = &ring->wa_ctx;

        WARN_ON(ring->id != RCS);

        /* update this when WA for higher Gen are added */
        if (INTEL_INFO(ring->dev)->gen > 9) {
                DRM_ERROR("WA batch buffer is not initialized for Gen%d\n",
                          INTEL_INFO(ring->dev)->gen);
                return 0;
        }

        /* some WA perform writes to scratch page, ensure it is valid */
        if (ring->scratch.obj == NULL) {
                DRM_ERROR("scratch page not allocated for %s\n", ring->name);
                return -EINVAL;
        }

        ret = lrc_setup_wa_ctx_obj(ring, PAGE_SIZE);
        if (ret) {
                DRM_DEBUG_DRIVER("Failed to setup context WA page: %d\n", ret);
                return ret;
        }

        page = i915_gem_object_get_page(wa_ctx->obj, 0);
        batch = kmap_atomic(page);
        offset = 0;

        if (INTEL_INFO(ring->dev)->gen == 8) {
                ret = gen8_init_indirectctx_bb(ring,
                                               &wa_ctx->indirect_ctx,
                                               batch,
                                               &offset);
                if (ret)
                        goto out;

                ret = gen8_init_perctx_bb(ring,
                                          &wa_ctx->per_ctx,
                                          batch,
                                          &offset);
                if (ret)
                        goto out;
        } else if (INTEL_INFO(ring->dev)->gen == 9) {
                ret = gen9_init_indirectctx_bb(ring,
                                               &wa_ctx->indirect_ctx,
                                               batch,
                                               &offset);
                if (ret)
                        goto out;

                ret = gen9_init_perctx_bb(ring,
                                          &wa_ctx->per_ctx,
                                          batch,
                                          &offset);
                if (ret)
                        goto out;
        }

out:
        kunmap_atomic(batch);
        if (ret)
                lrc_destroy_wa_ctx_obj(ring);

        return ret;
}

static int gen8_init_common_ring(struct intel_engine_cs *ring)
{
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;

        I915_WRITE_IMR(ring, ~(ring->irq_enable_mask | ring->irq_keep_mask));
        I915_WRITE(RING_HWSTAM(ring->mmio_base), 0xffffffff);

        if (ring->status_page.obj) {
                I915_WRITE(RING_HWS_PGA(ring->mmio_base),
                           (u32)ring->status_page.gfx_addr);
                POSTING_READ(RING_HWS_PGA(ring->mmio_base));
        }

        I915_WRITE(RING_MODE_GEN7(ring),
                   _MASKED_BIT_DISABLE(GFX_REPLAY_MODE) |
                   _MASKED_BIT_ENABLE(GFX_RUN_LIST_ENABLE));
        POSTING_READ(RING_MODE_GEN7(ring));
        ring->next_context_status_buffer = 0;
        DRM_DEBUG_DRIVER("Execlists enabled for %s\n", ring->name);

        memset(&ring->hangcheck, 0, sizeof(ring->hangcheck));

        return 0;
}

static int gen8_init_render_ring(struct intel_engine_cs *ring)
{
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;

        ret = gen8_init_common_ring(ring);
        if (ret)
                return ret;

        /* We need to disable the AsyncFlip performance optimisations in order
         * to use MI_WAIT_FOR_EVENT within the CS. It should already be
         * programmed to '1' on all products.
         *
         * WaDisableAsyncFlipPerfMode:snb,ivb,hsw,vlv,bdw,chv
         */
        I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(ASYNC_FLIP_PERF_DISABLE));

        I915_WRITE(INSTPM, _MASKED_BIT_ENABLE(INSTPM_FORCE_ORDERING));

        return init_workarounds_ring(ring);
}

static int gen9_init_render_ring(struct intel_engine_cs *ring)
{
        int ret;

        ret = gen8_init_common_ring(ring);
        if (ret)
                return ret;

        return init_workarounds_ring(ring);
}

static int intel_logical_ring_emit_pdps(struct drm_i915_gem_request *req)
{
        struct i915_hw_ppgtt *ppgtt = req->ctx->ppgtt;
        struct intel_engine_cs *ring = req->ring;
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        const int num_lri_cmds = GEN8_LEGACY_PDPES * 2;
        int i, ret;

        ret = intel_logical_ring_begin(req, num_lri_cmds * 2 + 2);
        if (ret)
                return ret;

        intel_logical_ring_emit(ringbuf, MI_LOAD_REGISTER_IMM(num_lri_cmds));
        for (i = GEN8_LEGACY_PDPES - 1; i >= 0; i--) {
                const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);

                intel_logical_ring_emit(ringbuf, GEN8_RING_PDP_UDW(ring, i));
                intel_logical_ring_emit(ringbuf, upper_32_bits(pd_daddr));
                intel_logical_ring_emit(ringbuf, GEN8_RING_PDP_LDW(ring, i));
                intel_logical_ring_emit(ringbuf, lower_32_bits(pd_daddr));
        }

        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static int gen8_emit_bb_start(struct drm_i915_gem_request *req,
                              u64 offset, unsigned dispatch_flags)
{
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        bool ppgtt = !(dispatch_flags & I915_DISPATCH_SECURE);
        int ret;

        /* Don't rely in hw updating PDPs, specially in lite-restore.
         * Ideally, we should set Force PD Restore in ctx descriptor,
         * but we can't. Force Restore would be a second option, but
         * it is unsafe in case of lite-restore (because the ctx is
         * not idle). PML4 is allocated during ppgtt init so this is
         * not needed in 48-bit.*/
        if (req->ctx->ppgtt &&
            (intel_ring_flag(req->ring) & req->ctx->ppgtt->pd_dirty_rings)) {
                if (!USES_FULL_48BIT_PPGTT(req->i915) &&
                    !intel_vgpu_active(req->i915->dev)) {
                        ret = intel_logical_ring_emit_pdps(req);
                        if (ret)
                                return ret;
                }

                req->ctx->ppgtt->pd_dirty_rings &= ~intel_ring_flag(req->ring);
        }

        ret = intel_logical_ring_begin(req, 4);
        if (ret)
                return ret;

        /* FIXME(BDW): Address space and security selectors. */
        intel_logical_ring_emit(ringbuf, MI_BATCH_BUFFER_START_GEN8 |
                                (ppgtt<<8) |
                                (dispatch_flags & I915_DISPATCH_RS ?
                                 MI_BATCH_RESOURCE_STREAMER : 0));
        intel_logical_ring_emit(ringbuf, lower_32_bits(offset));
        intel_logical_ring_emit(ringbuf, upper_32_bits(offset));
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static bool gen8_logical_ring_get_irq(struct intel_engine_cs *ring)
{
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        unsigned long flags;

        if (WARN_ON(!intel_irqs_enabled(dev_priv)))
                return false;

        spin_lock_irqsave(&dev_priv->irq_lock, flags);
        if (ring->irq_refcount++ == 0) {
                I915_WRITE_IMR(ring, ~(ring->irq_enable_mask | ring->irq_keep_mask));
                POSTING_READ(RING_IMR(ring->mmio_base));
        }
        spin_unlock_irqrestore(&dev_priv->irq_lock, flags);

        return true;
}

static void gen8_logical_ring_put_irq(struct intel_engine_cs *ring)
{
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        unsigned long flags;

        spin_lock_irqsave(&dev_priv->irq_lock, flags);
        if (--ring->irq_refcount == 0) {
                I915_WRITE_IMR(ring, ~ring->irq_keep_mask);
                POSTING_READ(RING_IMR(ring->mmio_base));
        }
        spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
}

static int gen8_emit_flush(struct drm_i915_gem_request *request,
                           u32 invalidate_domains,
                           u32 unused)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        struct intel_engine_cs *ring = ringbuf->ring;
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        uint32_t cmd;
        int ret;

        ret = intel_logical_ring_begin(request, 4);
        if (ret)
                return ret;

        cmd = MI_FLUSH_DW + 1;

        /* We always require a command barrier so that subsequent
         * commands, such as breadcrumb interrupts, are strictly ordered
         * wrt the contents of the write cache being flushed to memory
         * (and thus being coherent from the CPU).
         */
        cmd |= MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW;

        if (invalidate_domains & I915_GEM_GPU_DOMAINS) {
                cmd |= MI_INVALIDATE_TLB;
                if (ring == &dev_priv->ring[VCS])
                        cmd |= MI_INVALIDATE_BSD;
        }

        intel_logical_ring_emit(ringbuf, cmd);
        intel_logical_ring_emit(ringbuf,
                                I915_GEM_HWS_SCRATCH_ADDR |
                                MI_FLUSH_DW_USE_GTT);
        intel_logical_ring_emit(ringbuf, 0); /* upper addr */
        intel_logical_ring_emit(ringbuf, 0); /* value */
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static int gen8_emit_flush_render(struct drm_i915_gem_request *request,
                                  u32 invalidate_domains,
                                  u32 flush_domains)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        struct intel_engine_cs *ring = ringbuf->ring;
        u32 scratch_addr = ring->scratch.gtt_offset + 2 * CACHELINE_BYTES;
        bool vf_flush_wa;
        u32 flags = 0;
        int ret;

        flags |= PIPE_CONTROL_CS_STALL;

        if (flush_domains) {
                flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
        }

        if (invalidate_domains) {
                flags |= PIPE_CONTROL_TLB_INVALIDATE;
                flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_VF_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_CONST_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_STATE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_QW_WRITE;
                flags |= PIPE_CONTROL_GLOBAL_GTT_IVB;
        }

        /*
         * On GEN9+ Before VF_CACHE_INVALIDATE we need to emit a NULL pipe
         * control.
         */
        vf_flush_wa = INTEL_INFO(ring->dev)->gen >= 9 &&
                      flags & PIPE_CONTROL_VF_CACHE_INVALIDATE;

        ret = intel_logical_ring_begin(request, vf_flush_wa ? 12 : 6);
        if (ret)
                return ret;

        if (vf_flush_wa) {
                intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(6));
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
        }

        intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(6));
        intel_logical_ring_emit(ringbuf, flags);
        intel_logical_ring_emit(ringbuf, scratch_addr);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static u32 gen8_get_seqno(struct intel_engine_cs *ring, bool lazy_coherency)
{
        return intel_read_status_page(ring, I915_GEM_HWS_INDEX);
}

static void gen8_set_seqno(struct intel_engine_cs *ring, u32 seqno)
{
        intel_write_status_page(ring, I915_GEM_HWS_INDEX, seqno);
}

static u32 bxt_a_get_seqno(struct intel_engine_cs *ring, bool lazy_coherency)
{

        /*
         * On BXT A steppings there is a HW coherency issue whereby the
         * MI_STORE_DATA_IMM storing the completed request's seqno
         * occasionally doesn't invalidate the CPU cache. Work around this by
         * clflushing the corresponding cacheline whenever the caller wants
         * the coherency to be guaranteed. Note that this cacheline is known
         * to be clean at this point, since we only write it in
         * bxt_a_set_seqno(), where we also do a clflush after the write. So
         * this clflush in practice becomes an invalidate operation.
         */

        if (!lazy_coherency)
                intel_flush_status_page(ring, I915_GEM_HWS_INDEX);

        return intel_read_status_page(ring, I915_GEM_HWS_INDEX);
}

static void bxt_a_set_seqno(struct intel_engine_cs *ring, u32 seqno)
{
        intel_write_status_page(ring, I915_GEM_HWS_INDEX, seqno);

        /* See bxt_a_get_seqno() explaining the reason for the clflush. */
        intel_flush_status_page(ring, I915_GEM_HWS_INDEX);
}

static int gen8_emit_request(struct drm_i915_gem_request *request)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        struct intel_engine_cs *ring = ringbuf->ring;
        u32 cmd;
        int ret;

        /*
         * Reserve space for 2 NOOPs at the end of each request to be
         * used as a workaround for not being allowed to do lite
         * restore with HEAD==TAIL (WaIdleLiteRestore).
         */
        ret = intel_logical_ring_begin(request, 8);
        if (ret)
                return ret;

        cmd = MI_STORE_DWORD_IMM_GEN4;
        cmd |= MI_GLOBAL_GTT;

        intel_logical_ring_emit(ringbuf, cmd);
        intel_logical_ring_emit(ringbuf,
                                (ring->status_page.gfx_addr +
                                (I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT)));
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request));
        intel_logical_ring_emit(ringbuf, MI_USER_INTERRUPT);
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance_and_submit(request);

        /*
         * Here we add two extra NOOPs as padding to avoid
         * lite restore of a context with HEAD==TAIL.
         */
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static int intel_lr_context_render_state_init(struct drm_i915_gem_request *req)
{
        struct render_state so;
        int ret;

        ret = i915_gem_render_state_prepare(req->ring, &so);
        if (ret)
                return ret;

        if (so.rodata == NULL)
                return 0;

        ret = req->ring->emit_bb_start(req, so.ggtt_offset,
                                       I915_DISPATCH_SECURE);
        if (ret)
                goto out;

        ret = req->ring->emit_bb_start(req,
                                       (so.ggtt_offset + so.aux_batch_offset),
                                       I915_DISPATCH_SECURE);
        if (ret)
                goto out;

        i915_vma_move_to_active(i915_gem_obj_to_ggtt(so.obj), req);

out:
        i915_gem_render_state_fini(&so);
        return ret;
}

static int gen8_init_rcs_context(struct drm_i915_gem_request *req)
{
        int ret;

        ret = intel_logical_ring_workarounds_emit(req);
        if (ret)
                return ret;

        ret = intel_rcs_context_init_mocs(req);
        /*
         * Failing to program the MOCS is non-fatal.The system will not
         * run at peak performance. So generate an error and carry on.
         */
        if (ret)
                DRM_ERROR("MOCS failed to program: expect performance issues.\n");

        return intel_lr_context_render_state_init(req);
}

/**
 * intel_logical_ring_cleanup() - deallocate the Engine Command Streamer
 *
 * @ring: Engine Command Streamer.
 *
 */
void intel_logical_ring_cleanup(struct intel_engine_cs *ring)
{
        struct drm_i915_private *dev_priv;

        if (!intel_ring_initialized(ring))
                return;

        dev_priv = ring->dev->dev_private;

        intel_logical_ring_stop(ring);
        WARN_ON((I915_READ_MODE(ring) & MODE_IDLE) == 0);

        if (ring->cleanup)
                ring->cleanup(ring);

        i915_cmd_parser_fini_ring(ring);
        i915_gem_batch_pool_fini(&ring->batch_pool);

        if (ring->status_page.obj) {
                kunmap(sg_page(ring->status_page.obj->pages->sgl));
                ring->status_page.obj = NULL;
        }

        lrc_destroy_wa_ctx_obj(ring);
}

static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *ring)
{
        int ret;

        /* Intentionally left blank. */
        ring->buffer = NULL;

        ring->dev = dev;
        INIT_LIST_HEAD(&ring->active_list);
        INIT_LIST_HEAD(&ring->request_list);
        i915_gem_batch_pool_init(dev, &ring->batch_pool);
        init_waitqueue_head(&ring->irq_queue);

        INIT_LIST_HEAD(&ring->execlist_queue);
        INIT_LIST_HEAD(&ring->execlist_retired_req_list);
        spin_lock_init(&ring->execlist_lock);

        ret = i915_cmd_parser_init_ring(ring);
        if (ret)
                return ret;

        ret = intel_lr_context_deferred_create(ring->default_context, ring);

        return ret;
}

static int logical_render_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *ring = &dev_priv->ring[RCS];
        int ret;

        ring->name = "render ring";
        ring->id = RCS;
        ring->mmio_base = RENDER_RING_BASE;
        ring->irq_enable_mask =
                GT_RENDER_USER_INTERRUPT << GEN8_RCS_IRQ_SHIFT;
        ring->irq_keep_mask =
                GT_CONTEXT_SWITCH_INTERRUPT << GEN8_RCS_IRQ_SHIFT;
        if (HAS_L3_DPF(dev))
                ring->irq_keep_mask |= GT_RENDER_L3_PARITY_ERROR_INTERRUPT;

        if (INTEL_INFO(dev)->gen >= 9)
                ring->init_hw = gen9_init_render_ring;
        else
                ring->init_hw = gen8_init_render_ring;
        ring->init_context = gen8_init_rcs_context;
        ring->cleanup = intel_fini_pipe_control;
        if (IS_BROXTON(dev) && INTEL_REVID(dev) < BXT_REVID_B0) {
                ring->get_seqno = bxt_a_get_seqno;
                ring->set_seqno = bxt_a_set_seqno;
        } else {
                ring->get_seqno = gen8_get_seqno;
                ring->set_seqno = gen8_set_seqno;
        }
        ring->emit_request = gen8_emit_request;
        ring->emit_flush = gen8_emit_flush_render;
        ring->irq_get = gen8_logical_ring_get_irq;
        ring->irq_put = gen8_logical_ring_put_irq;
        ring->emit_bb_start = gen8_emit_bb_start;

        ring->dev = dev;

        ret = intel_init_pipe_control(ring);
        if (ret)
                return ret;

        ret = intel_init_workaround_bb(ring);
        if (ret) {
                /*
                 * We continue even if we fail to initialize WA batch
                 * because we only expect rare glitches but nothing
                 * critical to prevent us from using GPU
                 */
                DRM_ERROR("WA batch buffer initialization failed: %d\n",
                          ret);
        }

        ret = logical_ring_init(dev, ring);
        if (ret) {
                lrc_destroy_wa_ctx_obj(ring);
        }

        return ret;
}

static int logical_bsd_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *ring = &dev_priv->ring[VCS];

        ring->name = "bsd ring";
        ring->id = VCS;
        ring->mmio_base = GEN6_BSD_RING_BASE;
        ring->irq_enable_mask =
                GT_RENDER_USER_INTERRUPT << GEN8_VCS1_IRQ_SHIFT;
        ring->irq_keep_mask =
                GT_CONTEXT_SWITCH_INTERRUPT << GEN8_VCS1_IRQ_SHIFT;

        ring->init_hw = gen8_init_common_ring;
        if (IS_BROXTON(dev) && INTEL_REVID(dev) < BXT_REVID_B0) {
                ring->get_seqno = bxt_a_get_seqno;
                ring->set_seqno = bxt_a_set_seqno;
        } else {
                ring->get_seqno = gen8_get_seqno;
                ring->set_seqno = gen8_set_seqno;
        }
        ring->emit_request = gen8_emit_request;
        ring->emit_flush = gen8_emit_flush;
        ring->irq_get = gen8_logical_ring_get_irq;
        ring->irq_put = gen8_logical_ring_put_irq;
        ring->emit_bb_start = gen8_emit_bb_start;

        return logical_ring_init(dev, ring);
}

static int logical_bsd2_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *ring = &dev_priv->ring[VCS2];

        ring->name = "bds2 ring";
        ring->id = VCS2;
        ring->mmio_base = GEN8_BSD2_RING_BASE;
        ring->irq_enable_mask =
                GT_RENDER_USER_INTERRUPT << GEN8_VCS2_IRQ_SHIFT;
        ring->irq_keep_mask =
                GT_CONTEXT_SWITCH_INTERRUPT << GEN8_VCS2_IRQ_SHIFT;

        ring->init_hw = gen8_init_common_ring;
        ring->get_seqno = gen8_get_seqno;
        ring->set_seqno = gen8_set_seqno;
        ring->emit_request = gen8_emit_request;
        ring->emit_flush = gen8_emit_flush;
        ring->irq_get = gen8_logical_ring_get_irq;
        ring->irq_put = gen8_logical_ring_put_irq;
        ring->emit_bb_start = gen8_emit_bb_start;

        return logical_ring_init(dev, ring);
}

static int logical_blt_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *ring = &dev_priv->ring[BCS];

        ring->name = "blitter ring";
        ring->id = BCS;
        ring->mmio_base = BLT_RING_BASE;
        ring->irq_enable_mask =
                GT_RENDER_USER_INTERRUPT << GEN8_BCS_IRQ_SHIFT;
        ring->irq_keep_mask =
                GT_CONTEXT_SWITCH_INTERRUPT << GEN8_BCS_IRQ_SHIFT;

        ring->init_hw = gen8_init_common_ring;
        if (IS_BROXTON(dev) && INTEL_REVID(dev) < BXT_REVID_B0) {
                ring->get_seqno = bxt_a_get_seqno;
                ring->set_seqno = bxt_a_set_seqno;
        } else {
                ring->get_seqno = gen8_get_seqno;
                ring->set_seqno = gen8_set_seqno;
        }
        ring->emit_request = gen8_emit_request;
        ring->emit_flush = gen8_emit_flush;
        ring->irq_get = gen8_logical_ring_get_irq;
        ring->irq_put = gen8_logical_ring_put_irq;
        ring->emit_bb_start = gen8_emit_bb_start;

        return logical_ring_init(dev, ring);
}

static int logical_vebox_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *ring = &dev_priv->ring[VECS];

        ring->name = "video enhancement ring";
        ring->id = VECS;
        ring->mmio_base = VEBOX_RING_BASE;
        ring->irq_enable_mask =
                GT_RENDER_USER_INTERRUPT << GEN8_VECS_IRQ_SHIFT;
        ring->irq_keep_mask =
                GT_CONTEXT_SWITCH_INTERRUPT << GEN8_VECS_IRQ_SHIFT;

        ring->init_hw = gen8_init_common_ring;
        if (IS_BROXTON(dev) && INTEL_REVID(dev) < BXT_REVID_B0) {
                ring->get_seqno = bxt_a_get_seqno;
                ring->set_seqno = bxt_a_set_seqno;
        } else {
                ring->get_seqno = gen8_get_seqno;
                ring->set_seqno = gen8_set_seqno;
        }
        ring->emit_request = gen8_emit_request;
        ring->emit_flush = gen8_emit_flush;
        ring->irq_get = gen8_logical_ring_get_irq;
        ring->irq_put = gen8_logical_ring_put_irq;
        ring->emit_bb_start = gen8_emit_bb_start;

        return logical_ring_init(dev, ring);
}

/**
 * intel_logical_rings_init() - allocate, populate and init the Engine Command Streamers
 * @dev: DRM device.
 *
 * This function inits the engines for an Execlists submission style (the equivalent in the
 * legacy ringbuffer submission world would be i915_gem_init_rings). It does it only for
 * those engines that are present in the hardware.
 *
 * Return: non-zero if the initialization failed.
 */
int intel_logical_rings_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;

        ret = logical_render_ring_init(dev);
        if (ret)
                return ret;

        if (HAS_BSD(dev)) {
                ret = logical_bsd_ring_init(dev);
                if (ret)
                        goto cleanup_render_ring;
        }

        if (HAS_BLT(dev)) {
                ret = logical_blt_ring_init(dev);
                if (ret)
                        goto cleanup_bsd_ring;
        }

        if (HAS_VEBOX(dev)) {
                ret = logical_vebox_ring_init(dev);
                if (ret)
                        goto cleanup_blt_ring;
        }

        if (HAS_BSD2(dev)) {
                ret = logical_bsd2_ring_init(dev);
                if (ret)
                        goto cleanup_vebox_ring;
        }

        ret = i915_gem_set_seqno(dev, ((u32)~0 - 0x1000));
        if (ret)
                goto cleanup_bsd2_ring;

        return 0;

cleanup_bsd2_ring:
        intel_logical_ring_cleanup(&dev_priv->ring[VCS2]);
cleanup_vebox_ring:
        intel_logical_ring_cleanup(&dev_priv->ring[VECS]);
cleanup_blt_ring:
        intel_logical_ring_cleanup(&dev_priv->ring[BCS]);
cleanup_bsd_ring:
        intel_logical_ring_cleanup(&dev_priv->ring[VCS]);
cleanup_render_ring:
        intel_logical_ring_cleanup(&dev_priv->ring[RCS]);

        return ret;
}

static u32
make_rpcs(struct drm_device *dev)
{
        u32 rpcs = 0;

        /*
         * No explicit RPCS request is needed to ensure full
         * slice/subslice/EU enablement prior to Gen9.
        */
        if (INTEL_INFO(dev)->gen < 9)
                return 0;

        /*
         * Starting in Gen9, render power gating can leave
         * slice/subslice/EU in a partially enabled state. We
         * must make an explicit request through RPCS for full
         * enablement.
        */
        if (INTEL_INFO(dev)->has_slice_pg) {
                rpcs |= GEN8_RPCS_S_CNT_ENABLE;
                rpcs |= INTEL_INFO(dev)->slice_total <<
                        GEN8_RPCS_S_CNT_SHIFT;
                rpcs |= GEN8_RPCS_ENABLE;
        }

        if (INTEL_INFO(dev)->has_subslice_pg) {
                rpcs |= GEN8_RPCS_SS_CNT_ENABLE;
                rpcs |= INTEL_INFO(dev)->subslice_per_slice <<
                        GEN8_RPCS_SS_CNT_SHIFT;
                rpcs |= GEN8_RPCS_ENABLE;
        }

        if (INTEL_INFO(dev)->has_eu_pg) {
                rpcs |= INTEL_INFO(dev)->eu_per_subslice <<
                        GEN8_RPCS_EU_MIN_SHIFT;
                rpcs |= INTEL_INFO(dev)->eu_per_subslice <<
                        GEN8_RPCS_EU_MAX_SHIFT;
                rpcs |= GEN8_RPCS_ENABLE;
        }

        return rpcs;
}

static int
populate_lr_context(struct intel_context *ctx, struct drm_i915_gem_object *ctx_obj,
                    struct intel_engine_cs *ring, struct intel_ringbuffer *ringbuf)
{
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct i915_hw_ppgtt *ppgtt = ctx->ppgtt;
        struct page *page;
        uint32_t *reg_state;
        int ret;

        if (!ppgtt)
                ppgtt = dev_priv->mm.aliasing_ppgtt;

        ret = i915_gem_object_set_to_cpu_domain(ctx_obj, true);
        if (ret) {
                DRM_DEBUG_DRIVER("Could not set to CPU domain\n");
                return ret;
        }

        ret = i915_gem_object_get_pages(ctx_obj);
        if (ret) {
                DRM_DEBUG_DRIVER("Could not get object pages\n");
                return ret;
        }

        i915_gem_object_pin_pages(ctx_obj);

        /* The second page of the context object contains some fields which must
         * be set up prior to the first execution. */
        page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
        reg_state = kmap_atomic(page);

        /* A context is actually a big batch buffer with several MI_LOAD_REGISTER_IMM
         * commands followed by (reg, value) pairs. The values we are setting here are
         * only for the first context restore: on a subsequent save, the GPU will
         * recreate this batchbuffer with new values (including all the missing
         * MI_LOAD_REGISTER_IMM commands that we are not initializing here). */
        if (ring->id == RCS)
                reg_state[CTX_LRI_HEADER_0] = MI_LOAD_REGISTER_IMM(14);
        else
                reg_state[CTX_LRI_HEADER_0] = MI_LOAD_REGISTER_IMM(11);
        reg_state[CTX_LRI_HEADER_0] |= MI_LRI_FORCE_POSTED;
        reg_state[CTX_CONTEXT_CONTROL] = RING_CONTEXT_CONTROL(ring);
        reg_state[CTX_CONTEXT_CONTROL+1] =
                _MASKED_BIT_ENABLE(CTX_CTRL_INHIBIT_SYN_CTX_SWITCH |
                                   CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT |
                                   CTX_CTRL_RS_CTX_ENABLE);
        reg_state[CTX_RING_HEAD] = RING_HEAD(ring->mmio_base);
        reg_state[CTX_RING_HEAD+1] = 0;
        reg_state[CTX_RING_TAIL] = RING_TAIL(ring->mmio_base);
        reg_state[CTX_RING_TAIL+1] = 0;
        reg_state[CTX_RING_BUFFER_START] = RING_START(ring->mmio_base);
        /* Ring buffer start address is not known until the buffer is pinned.
         * It is written to the context image in execlists_update_context()
         */
        reg_state[CTX_RING_BUFFER_CONTROL] = RING_CTL(ring->mmio_base);
        reg_state[CTX_RING_BUFFER_CONTROL+1] =
                        ((ringbuf->size - PAGE_SIZE) & RING_NR_PAGES) | RING_VALID;
        reg_state[CTX_BB_HEAD_U] = ring->mmio_base + 0x168;
        reg_state[CTX_BB_HEAD_U+1] = 0;
        reg_state[CTX_BB_HEAD_L] = ring->mmio_base + 0x140;
        reg_state[CTX_BB_HEAD_L+1] = 0;
        reg_state[CTX_BB_STATE] = ring->mmio_base + 0x110;
        reg_state[CTX_BB_STATE+1] = (1<<5);
        reg_state[CTX_SECOND_BB_HEAD_U] = ring->mmio_base + 0x11c;
        reg_state[CTX_SECOND_BB_HEAD_U+1] = 0;
        reg_state[CTX_SECOND_BB_HEAD_L] = ring->mmio_base + 0x114;
        reg_state[CTX_SECOND_BB_HEAD_L+1] = 0;
        reg_state[CTX_SECOND_BB_STATE] = ring->mmio_base + 0x118;
        reg_state[CTX_SECOND_BB_STATE+1] = 0;
        if (ring->id == RCS) {
                reg_state[CTX_BB_PER_CTX_PTR] = ring->mmio_base + 0x1c0;
                reg_state[CTX_BB_PER_CTX_PTR+1] = 0;
                reg_state[CTX_RCS_INDIRECT_CTX] = ring->mmio_base + 0x1c4;
                reg_state[CTX_RCS_INDIRECT_CTX+1] = 0;
                reg_state[CTX_RCS_INDIRECT_CTX_OFFSET] = ring->mmio_base + 0x1c8;
                reg_state[CTX_RCS_INDIRECT_CTX_OFFSET+1] = 0;
                if (ring->wa_ctx.obj) {
                        struct i915_ctx_workarounds *wa_ctx = &ring->wa_ctx;
                        uint32_t ggtt_offset = i915_gem_obj_ggtt_offset(wa_ctx->obj);

                        reg_state[CTX_RCS_INDIRECT_CTX+1] =
                                (ggtt_offset + wa_ctx->indirect_ctx.offset * sizeof(uint32_t)) |
                                (wa_ctx->indirect_ctx.size / CACHELINE_DWORDS);

                        reg_state[CTX_RCS_INDIRECT_CTX_OFFSET+1] =
                                CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT << 6;

                        reg_state[CTX_BB_PER_CTX_PTR+1] =
                                (ggtt_offset + wa_ctx->per_ctx.offset * sizeof(uint32_t)) |
                                0x01;
                }
        }
        reg_state[CTX_LRI_HEADER_1] = MI_LOAD_REGISTER_IMM(9);
        reg_state[CTX_LRI_HEADER_1] |= MI_LRI_FORCE_POSTED;
        reg_state[CTX_CTX_TIMESTAMP] = ring->mmio_base + 0x3a8;
        reg_state[CTX_CTX_TIMESTAMP+1] = 0;
        reg_state[CTX_PDP3_UDW] = GEN8_RING_PDP_UDW(ring, 3);
        reg_state[CTX_PDP3_LDW] = GEN8_RING_PDP_LDW(ring, 3);
        reg_state[CTX_PDP2_UDW] = GEN8_RING_PDP_UDW(ring, 2);
        reg_state[CTX_PDP2_LDW] = GEN8_RING_PDP_LDW(ring, 2);
        reg_state[CTX_PDP1_UDW] = GEN8_RING_PDP_UDW(ring, 1);
        reg_state[CTX_PDP1_LDW] = GEN8_RING_PDP_LDW(ring, 1);
        reg_state[CTX_PDP0_UDW] = GEN8_RING_PDP_UDW(ring, 0);
        reg_state[CTX_PDP0_LDW] = GEN8_RING_PDP_LDW(ring, 0);

        if (USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
                /* 64b PPGTT (48bit canonical)
                 * PDP0_DESCRIPTOR contains the base address to PML4 and
                 * other PDP Descriptors are ignored.
                 */
                ASSIGN_CTX_PML4(ppgtt, reg_state);
        } else {
                /* 32b PPGTT
                 * PDP*_DESCRIPTOR contains the base address of space supported.
                 * With dynamic page allocation, PDPs may not be allocated at
                 * this point. Point the unallocated PDPs to the scratch page
                 */
                ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
                ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
                ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
                ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
        }

        if (ring->id == RCS) {
                reg_state[CTX_LRI_HEADER_2] = MI_LOAD_REGISTER_IMM(1);
                reg_state[CTX_R_PWR_CLK_STATE] = GEN8_R_PWR_CLK_STATE;
                reg_state[CTX_R_PWR_CLK_STATE+1] = make_rpcs(dev);
        }

        kunmap_atomic(reg_state);

        ctx_obj->dirty = 1;
        set_page_dirty(page);
        i915_gem_object_unpin_pages(ctx_obj);

        return 0;
}

/**
 * intel_lr_context_free() - free the LRC specific bits of a context
 * @ctx: the LR context to free.
 *
 * The real context freeing is done in i915_gem_context_free: this only
 * takes care of the bits that are LRC related: the per-engine backing
 * objects and the logical ringbuffer.
 */
void intel_lr_context_free(struct intel_context *ctx)
{
        int i;

        for (i = 0; i < I915_NUM_RINGS; i++) {
                struct drm_i915_gem_object *ctx_obj = ctx->engine[i].state;

                if (ctx_obj) {
                        struct intel_ringbuffer *ringbuf =
                                        ctx->engine[i].ringbuf;
                        struct intel_engine_cs *ring = ringbuf->ring;

                        if (ctx == ring->default_context) {
                                intel_unpin_ringbuffer_obj(ringbuf);
                                i915_gem_object_ggtt_unpin(ctx_obj);
                        }
                        WARN_ON(ctx->engine[ring->id].pin_count);
                        intel_ringbuffer_free(ringbuf);
                        drm_gem_object_unreference(&ctx_obj->base);
                }
        }
}

static uint32_t get_lr_context_size(struct intel_engine_cs *ring)
{
        int ret = 0;

        WARN_ON(INTEL_INFO(ring->dev)->gen < 8);

        switch (ring->id) {
        case RCS:
                if (INTEL_INFO(ring->dev)->gen >= 9)
                        ret = GEN9_LR_CONTEXT_RENDER_SIZE;
                else
                        ret = GEN8_LR_CONTEXT_RENDER_SIZE;
                break;
        case VCS:
        case BCS:
        case VECS:
        case VCS2:
                ret = GEN8_LR_CONTEXT_OTHER_SIZE;
                break;
        }

        return ret;
}

static void lrc_setup_hardware_status_page(struct intel_engine_cs *ring,
                struct drm_i915_gem_object *default_ctx_obj)
{
        struct drm_i915_private *dev_priv = ring->dev->dev_private;
        struct page *page;

        /* The HWSP is part of the default context object in LRC mode. */
        ring->status_page.gfx_addr = i915_gem_obj_ggtt_offset(default_ctx_obj)
                        + LRC_PPHWSP_PN * PAGE_SIZE;
        page = i915_gem_object_get_page(default_ctx_obj, LRC_PPHWSP_PN);
        ring->status_page.page_addr = kmap(page);
        ring->status_page.obj = default_ctx_obj;

        I915_WRITE(RING_HWS_PGA(ring->mmio_base),
                        (u32)ring->status_page.gfx_addr);
        POSTING_READ(RING_HWS_PGA(ring->mmio_base));
}

/**
 * intel_lr_context_deferred_create() - create the LRC specific bits of a context
 * @ctx: LR context to create.
 * @ring: engine to be used with the context.
 *
 * This function can be called more than once, with different engines, if we plan
 * to use the context with them. The context backing objects and the ringbuffers
 * (specially the ringbuffer backing objects) suck a lot of memory up, and that's why
 * the creation is a deferred call: it's better to make sure first that we need to use
 * a given ring with the context.
 *
 * Return: non-zero on error.
 */
int intel_lr_context_deferred_create(struct intel_context *ctx,
                                     struct intel_engine_cs *ring)
{
        const bool is_global_default_ctx = (ctx == ring->default_context);
        struct drm_device *dev = ring->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct drm_i915_gem_object *ctx_obj;
        uint32_t context_size;
        struct intel_ringbuffer *ringbuf;
        int ret;

        WARN_ON(ctx->legacy_hw_ctx.rcs_state != NULL);
        WARN_ON(ctx->engine[ring->id].state);

        context_size = round_up(get_lr_context_size(ring), 4096);

        /* One extra page as the sharing data between driver and GuC */
        context_size += PAGE_SIZE * LRC_PPHWSP_PN;

        ctx_obj = i915_gem_alloc_object(dev, context_size);
        if (!ctx_obj) {
                DRM_DEBUG_DRIVER("Alloc LRC backing obj failed.\n");
                return -ENOMEM;
        }

        if (is_global_default_ctx) {
                ret = i915_gem_obj_ggtt_pin(ctx_obj, GEN8_LR_CONTEXT_ALIGN,
                                PIN_OFFSET_BIAS | GUC_WOPCM_TOP);
                if (ret) {
                        DRM_DEBUG_DRIVER("Pin LRC backing obj failed: %d\n",
                                        ret);
                        drm_gem_object_unreference(&ctx_obj->base);
                        return ret;
                }

                /* Invalidate GuC TLB. */
                if (i915.enable_guc_submission)
                        I915_WRITE(GEN8_GTCR, GEN8_GTCR_INVALIDATE);
        }

        ringbuf = intel_engine_create_ringbuffer(ring, 4 * PAGE_SIZE);
        if (IS_ERR(ringbuf)) {
                ret = PTR_ERR(ringbuf);
                goto error_unpin_ctx;
        }

        if (is_global_default_ctx) {
                ret = intel_pin_and_map_ringbuffer_obj(dev, ringbuf);
                if (ret) {
                        DRM_ERROR(
                                  "Failed to pin and map ringbuffer %s: %d\n",
                                  ring->name, ret);
                        goto error_ringbuf;
                }
        }

        ret = populate_lr_context(ctx, ctx_obj, ring, ringbuf);
        if (ret) {
                DRM_DEBUG_DRIVER("Failed to populate LRC: %d\n", ret);
                goto error;
        }

        ctx->engine[ring->id].ringbuf = ringbuf;
        ctx->engine[ring->id].state = ctx_obj;

        if (ctx == ring->default_context)
                lrc_setup_hardware_status_page(ring, ctx_obj);
        else if (ring->id == RCS && !ctx->rcs_initialized) {
                if (ring->init_context) {
                        struct drm_i915_gem_request *req;

                        ret = i915_gem_request_alloc(ring, ctx, &req);
                        if (ret)
                                return ret;

                        ret = ring->init_context(req);
                        if (ret) {
                                DRM_ERROR("ring init context: %d\n", ret);
                                i915_gem_request_cancel(req);
                                ctx->engine[ring->id].ringbuf = NULL;
                                ctx->engine[ring->id].state = NULL;
                                goto error;
                        }

                        i915_add_request_no_flush(req);
                }

                ctx->rcs_initialized = true;
        }

        return 0;

error:
        if (is_global_default_ctx)
                intel_unpin_ringbuffer_obj(ringbuf);
error_ringbuf:
        intel_ringbuffer_free(ringbuf);
error_unpin_ctx:
        if (is_global_default_ctx)
                i915_gem_object_ggtt_unpin(ctx_obj);
        drm_gem_object_unreference(&ctx_obj->base);
        return ret;
}

void intel_lr_context_reset(struct drm_device *dev,
                        struct intel_context *ctx)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *ring;
        int i;

        for_each_ring(ring, dev_priv, i) {
                struct drm_i915_gem_object *ctx_obj =
                                ctx->engine[ring->id].state;
                struct intel_ringbuffer *ringbuf =
                                ctx->engine[ring->id].ringbuf;
                uint32_t *reg_state;
                struct page *page;

                if (!ctx_obj)
                        continue;

                if (i915_gem_object_get_pages(ctx_obj)) {
                        WARN(1, "Failed get_pages for context obj\n");
                        continue;
                }
                page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
                reg_state = kmap_atomic(page);

                reg_state[CTX_RING_HEAD+1] = 0;
                reg_state[CTX_RING_TAIL+1] = 0;

                kunmap_atomic(reg_state);

                ringbuf->head = 0;
                ringbuf->tail = 0;
        }
}