drm/msm: Don't overwrite hw fence in hw_init

Prior to the last commit, this could result in setting the GPU
written fence value back to an older value, if we had missed
updating completed_fence prior to suspend.  This was mostly
harmless as the GPU would eventually overwrite it again with
the correct value.  But we should just not do this.  Instead
just leave a sanity check that the fence looks plausible (in
case the GPU scribbled on memory).

Reported-by: Steev Klimaszewski <steev@kali.org>
Fixes: 95d1deb02a9c ("drm/msm/gem: Add fenced vma unpin")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Patchwork: https://patchwork.freedesktop.org/patch/490138/
Link: https://lore.kernel.org/r/20220618161120.3451993-2-robdclark@gmail.com

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index f944b69..efe9840 100644 (file)
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -498,10 +498,15 @@ int adreno_hw_init(struct msm_gpu *gpu)
 
                ring->cur = ring->start;
                ring->next = ring->start;
-
-               /* reset completed fence seqno: */
-               ring->memptrs->fence = ring->fctx->completed_fence;
                ring->memptrs->rptr = 0;
+
+               /* Detect and clean up an impossible fence, ie. if GPU managed
+                * to scribble something invalid, we don't want that to confuse
+                * us into mistakingly believing that submits have completed.
+                */
+               if (fence_before(ring->fctx->last_fence, ring->memptrs->fence)) {
+                       ring->memptrs->fence = ring->fctx->last_fence;
+               }
        }
 
        return 0;

diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index cedc88c..c8cd9bf 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -418,7 +418,7 @@ static void recover_worker(struct kthread_work *work)
                 * one more to clear the faulting submit
                 */
                if (ring == cur_ring)
-                       fence++;
+                       ring->memptrs->fence = ++fence;
 
                msm_update_fence(ring->fctx, fence);
        }