linux-kernel - [PATCH] drm/msm/adreno: fix updating ring fence

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Date:   Wed, 12 Aug 2020 17:03:09 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Rob Clark <robdclark@...omium.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Brian Masney <masneyb@...tation.org>,
        Takashi Iwai <tiwai@...e.de>,
        linux-arm-msm@...r.kernel.org (open list:DRM DRIVER FOR MSM ADRENO GPU),
        freedreno@...ts.freedesktop.org (open list:DRM DRIVER FOR MSM ADRENO
        GPU), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/msm/adreno: fix updating ring fence

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

We need to set it to the most recent completed fence, not the most
recent submitted.  Otherwise we have races where we think we can retire
submits that the GPU is not finished with, if the GPU doesn't manage to
overwrite the seqno before we look at it.

This can show up with hang recovery if one of the submits after the
crashing submit also hangs after it is replayed.

Fixes: f97decac5f4c ("drm/msm: Support multiple ringbuffers")
Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/msm/adreno/adreno_gpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index f9e3badf2fca..34e6242c1767 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -405,7 +405,7 @@ int adreno_hw_init(struct msm_gpu *gpu)
 		ring->next = ring->start;
 
 		/* reset completed fence seqno: */
-		ring->memptrs->fence = ring->seqno;
+		ring->memptrs->fence = ring->fctx->completed_fence;
 		ring->memptrs->rptr = 0;
 	}
 
-- 
2.26.2