drm/nouveau/fifo/gk104-: trigger mmu fault before attempting engine recovery

Greatly improves the chances of recovering the GPU from a CTXSW_TIMEOUT.

Tested with piglit's arb_shader_image_load_store-atomicity, which causes
GR to hang in such a way that recovery failed (CTXSW_TIMEOUT continually
re-triggers).

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
index e4e68f6..3a24788 100644 (file)
--- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
@@ -280,10 +280,13 @@ gk104_fifo_recover_chan(struct nvkm_fifo *base, int chid)
 static void
 gk104_fifo_recover_engn(struct gk104_fifo *fifo, int engn)
 {
+       struct nvkm_engine *engine = fifo->engine[engn].engine;
        struct nvkm_subdev *subdev = &fifo->base.engine.subdev;
+       struct nvkm_device *device = subdev->device;
        const u32 runl = fifo->engine[engn].runl;
        const u32 engm = BIT(engn);
        struct gk104_fifo_engine_status status;
+       int mmui = -1;
 
        assert_spin_locked(&fifo->base.lock);
        if (fifo->recover.engm & engm)
@@ -300,6 +303,44 @@ gk104_fifo_recover_engn(struct gk104_fifo *fifo, int engn)
                gk104_fifo_recover_chan(&fifo->base, status.chan->id);
        }
 
+       /* Determine MMU fault ID for the engine, if we're not being
+        * called from the fault handler already.
+        */
+       if (!status.faulted && engine) {
+               mmui = nvkm_top_fault_id(device, engine->subdev.index);
+               if (mmui < 0) {
+                       const struct nvkm_enum *en = fifo->func->fault.engine;
+                       for (; en && en->name; en++) {
+                               if (en->data2 == engine->subdev.index) {
+                                       mmui = en->value;
+                                       break;
+                               }
+                       }
+               }
+               WARN_ON(mmui < 0);
+       }
+
+       /* Trigger a MMU fault for the engine.
+        *
+        * No good idea why this is needed, but nvgpu does something similar,
+        * and it makes recovery from CTXSW_TIMEOUT a lot more reliable.
+        */
+       if (mmui >= 0) {
+               nvkm_wr32(device, 0x002a30 + (engn * 0x04), 0x00000100 | mmui);
+
+               /* Wait for fault to trigger. */
+               nvkm_msec(device, 2000,
+                       gk104_fifo_engine_status(fifo, engn, &status);
+                       if (status.faulted)
+                               break;
+               );
+
+               /* Release MMU fault trigger, and ACK the fault. */
+               nvkm_wr32(device, 0x002a30 + (engn * 0x04), 0x00000000);
+               nvkm_wr32(device, 0x00259c, BIT(mmui));
+               nvkm_wr32(device, 0x002100, 0x10000000);
+       }
+
        /* Schedule recovery. */
        nvkm_warn(subdev, "engine %d: scheduled for recovery\n", engn);
        schedule_work(&fifo->recover.work);