From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date: Tue, 14 Feb 2023 05:09:55 +0300
Subject: [PATCH] drm/msm/a5xx: fix the emptyness check in the preempt code
References: bsc#1012628
Patch-mainline: 6.2.7
Git-commit: b4fb748f0b734ce1d2e7834998cc599fcbd25d67

[ Upstream commit b4fb748f0b734ce1d2e7834998cc599fcbd25d67 ]

Quoting Yassine: ring->memptrs->rptr is never updated and stays 0, so
the comparison always evaluates to false and get_next_ring always
returns ring 0 thinking it isn't empty.

Fix this by calling get_rptr() instead of reading rptr directly.

Reported-by: Yassine Oudjana <y.oudjana@protonmail.com>
Fixes: b1fc2839d2f9 ("drm/msm: Implement preemption for A5XX targets")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/522642/
Link: https://lore.kernel.org/r/20230214020956.164473-4-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/gpu/drm/msm/adreno/a5xx_preempt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/adreno/a5xx_preempt.c b/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
index 7658e898..7e0affd6 100644
--- a/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
+++ b/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
@@ -63,7 +63,7 @@ static struct msm_ringbuffer *get_next_ring(struct msm_gpu *gpu)
 		struct msm_ringbuffer *ring = gpu->rb[i];
 
 		spin_lock_irqsave(&ring->preempt_lock, flags);
-		empty = (get_wptr(ring) == ring->memptrs->rptr);
+		empty = (get_wptr(ring) == gpu->funcs->get_rptr(gpu, ring));
 		spin_unlock_irqrestore(&ring->preempt_lock, flags);
 
 		if (!empty)
-- 
2.35.3