drm/msm: Fix races managing the OOB state for timestamp vs timestamps.

stable inclusion
from stable-5.10.20
commit 2d130a893ef3b8532bbbb01a90656ba5e6518511
bugzilla: 50608

--------------------------------

[ Upstream commit 5f98b33b ]

Now that we're not racing with GPU setup, also fix races of timestamps
against other timestamps.  In freedreno CI, we were seeing this path trigger
timeouts on setting the GMU bit, producing:

[drm:_a6xx_gmu_set_oob] *ERROR* Timeout waiting for GMU OOB set GPU_SET: 0x0

and this triggered especially on the first set of tests right after
boot (it's probably easier to lose the race than one might think,
given that we start many tests in parallel, and waiting for NFS to
page in code probably means that lots of tests hit the same point of
screen init at the same time).  As of this patch, the message seems to
have completely gone away.
Signed-off-by: NEric Anholt <eric@anholt.net>
Fixes: 4b565ca5 ("drm/msm: Add A6XX device support")
Reviewed-by: NJordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: NRob Clark <robdclark@chromium.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

@@ -1066,6 +1066,9 @@ static int a6xx_get_timestamp(struct msm_gpu *gpu, uint64_t *value)
 {
 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 	struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
+	static DEFINE_MUTEX(perfcounter_oob);
+
+	mutex_lock(&perfcounter_oob);
 
 	/* Force the GPU power on so we can read this register */
 	a6xx_gmu_set_oob(&a6xx_gpu->gmu, GMU_OOB_PERFCOUNTER_SET);
@@ -1074,6 +1077,7 @@ static int a6xx_get_timestamp(struct msm_gpu *gpu, uint64_t *value)
 		REG_A6XX_RBBM_PERFCTR_CP_0_HI);
 
 	a6xx_gmu_clear_oob(&a6xx_gpu->gmu, GMU_OOB_PERFCOUNTER_SET);
+	mutex_unlock(&perfcounter_oob);
 	return 0;
 }