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SubjectRe: [PATCH 2/2] drm/msm: Don't overwrite hw fence in hw_init
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On 6/15/22 10:01 AM, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
>
> 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>
> ---
> drivers/gpu/drm/msm/adreno/adreno_gpu.c | 11 ++++++++---
> drivers/gpu/drm/msm/msm_gpu.c | 2 +-
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index e1aef4875e2f..dd044d557c7c 100644
> --- 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 b61078f0cd0f..8c00f9187c03 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -430,7 +430,7 @@ 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);
> }

Tested on the Lenovo Yoga C630

Tested-by: Steev Klimaszewski <steev@kali.org>

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