drm/i915: Drop ORIGIN_GTT for untracked GTT writes

If FBC is set on a framebuffer that is unmapped, all GTT faults will be
from a partial mapping. Writes by the user through the partial VMA are
then untracked by the FBC and so we must use the ORIGIN_CPU when flushing
the I915_GEM_DOMAIN_GTT.

v2: Keep ORIGIN_CPU for set-to-domain(.write=CPU)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-25-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 56d4393..9386523 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2198,6 +2198,7 @@ struct drm_i915_gem_object {
        unsigned int cache_dirty:1;
 
        atomic_t frontbuffer_bits;
+       unsigned int frontbuffer_ggtt_origin; /* write once */
 
        /** Current tiling stride for the object, if it's tiled. */
        unsigned int tiling_and_stride;
@@ -2205,7 +2206,6 @@ struct drm_i915_gem_object {
 #define TILING_MASK (FENCE_MINIMUM_STRIDE-1)
 #define STRIDE_MASK (~TILING_MASK)
 
-       unsigned int has_wc_mmap;
        /** Count of VMA actually bound by this object */
        unsigned int bind_count;
        unsigned int pin_display;

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e4c18c7..9811980 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1497,8 +1497,8 @@ err:
 static inline enum fb_op_origin
 write_origin(struct drm_i915_gem_object *obj, unsigned domain)
 {
-       return domain == I915_GEM_DOMAIN_GTT && !obj->has_wc_mmap ?
-              ORIGIN_GTT : ORIGIN_CPU;
+       return (domain == I915_GEM_DOMAIN_GTT ?
+               obj->frontbuffer_ggtt_origin : ORIGIN_CPU);
 }
 
 /**
@@ -1658,7 +1658,7 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
                up_write(&mm->mmap_sem);
 
                /* This may race, but that's ok, it only gets set */
-               WRITE_ONCE(obj->has_wc_mmap, true);
+               WRITE_ONCE(obj->frontbuffer_ggtt_origin, ORIGIN_CPU);
        }
        i915_gem_object_put_unlocked(obj);
        if (IS_ERR((void *)addr))
@@ -1761,6 +1761,11 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf)
                if (chunk_size >= obj->base.size >> PAGE_SHIFT)
                        view.type = I915_GGTT_VIEW_NORMAL;
 
+               /* Userspace is now writing through an untracked VMA, abandon
+                * all hope that the hardware is able to track future writes.
+                */
+               obj->frontbuffer_ggtt_origin = ORIGIN_CPU;
+
                vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, PIN_MAPPABLE);
        }
        if (IS_ERR(vma)) {
@@ -4093,6 +4098,7 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 
        obj->ops = ops;
 
+       obj->frontbuffer_ggtt_origin = ORIGIN_GTT;
        obj->madv = I915_MADV_WILLNEED;
 
        i915_gem_info_add_obj(to_i915(obj->base.dev), obj->base.size);