linux-kernel - [PATCH] drm/msm/a6xx: Fix recovery vs runpm race

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Message-ID: <20231218155927.368881-1-robdclark@gmail.com>
Date: Mon, 18 Dec 2023 07:59:24 -0800
From: Rob Clark <robdclark@...il.com>
To: dri-devel@...ts.freedesktop.org
Cc: freedreno@...ts.freedesktop.org,
	linux-arm-msm@...r.kernel.org,
	Rob Clark <robdclark@...omium.org>,
	David Heidelberg <david.heidelberg@...labora.com>,
	Rob Clark <robdclark@...il.com>,
	Abhinav Kumar <quic_abhinavk@...cinc.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Sean Paul <sean@...rly.run>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Akhil P Oommen <quic_akhilpo@...cinc.com>,
	Danylo Piliaiev <dpiliaiev@...lia.com>,
	Bjorn Andersson <andersson@...nel.org>,
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/msm/a6xx: Fix recovery vs runpm race

From: Rob Clark <robdclark@...omium.org>

a6xx_recover() is relying on the gpu lock to serialize against incoming
submits doing a runpm get, as it tries to temporarily balance out the
runpm gets with puts in order to power off the GPU.  Unfortunately this
gets worse when we (in a later patch) will move the runpm get out of the
scheduler thread/work to move it out of the fence signaling path.

Instead we can just simplify the whole thing by using force_suspend() /
force_resume() instead of trying to be clever.

Reported-by: David Heidelberg <david.heidelberg@...labora.com>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/10272
Fixes: abe2023b4cea ("drm/msm/gpu: Push gpu lock down past runpm")
Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index 268737e59131..a5660d63535b 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -1244,12 +1244,7 @@ static void a6xx_recover(struct msm_gpu *gpu)
 	dev_pm_genpd_add_notifier(gmu->cxpd, &gmu->pd_nb);
 	dev_pm_genpd_synced_poweroff(gmu->cxpd);
 
-	/* Drop the rpm refcount from active submits */
-	if (active_submits)
-		pm_runtime_put(&gpu->pdev->dev);
-
-	/* And the final one from recover worker */
-	pm_runtime_put_sync(&gpu->pdev->dev);
+	pm_runtime_force_suspend(&gpu->pdev->dev);
 
 	if (!wait_for_completion_timeout(&gmu->pd_gate, msecs_to_jiffies(1000)))
 		DRM_DEV_ERROR(&gpu->pdev->dev, "cx gdsc didn't collapse\n");
@@ -1258,10 +1253,7 @@ static void a6xx_recover(struct msm_gpu *gpu)
 
 	pm_runtime_use_autosuspend(&gpu->pdev->dev);
 
-	if (active_submits)
-		pm_runtime_get(&gpu->pdev->dev);
-
-	pm_runtime_get_sync(&gpu->pdev->dev);
+	pm_runtime_force_resume(&gpu->pdev->dev);
 
 	gpu->active_submits = active_submits;
 	mutex_unlock(&gpu->active_lock);
-- 
2.43.0