[PATCH 5.19 0441/1157] drm/msm: Fix fence rollover issue

Greg Kroah-Hartman
2022-08-15T23:54:53Z

From: Rob Clark <robdclark@chromium.org>

[ Upstream commit 2311720a0182756f175fbf4afc1fb76ac487b587 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/msm/msm_fence.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c
index 38e3323bc232..a47e5837c528 100644
--- 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);
}

--
2.35.1