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

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Message-Id: <20220815180457.256915051@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 19:56:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Rob Clark <robdclark@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.19 0441/1157] drm/msm: Fix fence rollover issue

From: Rob Clark <robdclark@...omium.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@...omium.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@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.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