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

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Date:   Mon, 17 Aug 2020 10:25:57 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel@...ts.freedesktop.org,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Brian Masney <masneyb@...tation.org>,
        Takashi Iwai <tiwai@...e.de>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/adreno: fix updating ring fence

On Wed, Aug 12, 2020 at 05:03:09PM -0700, Rob Clark wrote:
> 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.

Reviewed-by: Jordan Crouse <jcrouse@...eaurora.org>

> 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
> 

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