drm/msm: Fix fence rollover issue

And while we are at it, let's start the fence counter close to the
rollover point so that if issues slip in, they are more obvious.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Fixes: fde5de6cb461 ("drm/msm: move fence code to it's own file")
Fixes: 5f3aee4ceb5b ("drm/msm: Handle fence rollover")
Patchwork: https://patchwork.freedesktop.org/patch/489619/
Link: https://lore.kernel.org/r/20220615162435.3011793-1-robdclark@gmail.com
[DB: fixed the conflict while applying the patch]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c
index 38e3323bc2324ee2bae81d9a359405610cdc59f1..a47e5837c528f2d0fdf28a5eaf762b72ba126e34 100644 (file)
--- a/drivers/gpu/drm/msm/msm_fence.c
+++ b/drivers/gpu/drm/msm/msm_fence.c
@@ -28,6 +28,14 @@ msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr,
        fctx->fenceptr = fenceptr;
        spin_lock_init(&fctx->spinlock);
 
+       /*
+        * Start out close to the 32b fence rollover point, so we can
+        * catch bugs with fence comparisons.
+        */
+       fctx->last_fence = 0xffffff00;
+       fctx->completed_fence = fctx->last_fence;
+       *fctx->fenceptr = fctx->last_fence;
+
        return fctx;
 }
 
@@ -52,7 +60,8 @@ void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence)
        unsigned long flags;
 
        spin_lock_irqsave(&fctx->spinlock, flags);
-       fctx->completed_fence = max(fence, fctx->completed_fence);
+       if (fence_after(fence, fctx->completed_fence))
+               fctx->completed_fence = fence;
        spin_unlock_irqrestore(&fctx->spinlock, flags);
 }