From 5f98b33b04c02c0d9088c7486c59d058696782f9 Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Thu, 28 Jan 2021 13:03:31 -0800
Subject: drm/msm: Fix races managing the OOB state for timestamp vs
 timestamps.
Git-commit: 5f98b33b04c02c0d9088c7486c59d058696782f9
Patch-mainline: v5.12-rc1
References: bsc#1152489

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: Eric Anholt <eric@anholt.net>
Fixes: 4b565ca5a2cb ("drm/msm: Add A6XX device support")
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -762,6 +762,9 @@ static int a6xx_get_timestamp(struct msm
 {
 	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_GPU_SET);
@@ -770,6 +773,7 @@ static int a6xx_get_timestamp(struct msm
 		REG_A6XX_RBBM_PERFCTR_CP_0_HI);
 
 	a6xx_gmu_clear_oob(&a6xx_gpu->gmu, GMU_OOB_GPU_SET);
+	mutex_unlock(&perfcounter_oob);
 	return 0;
 }