linux-kernel - Re: [PATCH] drm/msm: Remove exclusive-fence hack

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Date:   Wed, 2 Nov 2022 09:00:06 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Christian König <christian.koenig@....com>
Cc:     dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Rob Clark <robdclark@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH] drm/msm: Remove exclusive-fence hack

On Wed, Nov 2, 2022 at 3:46 AM Christian König <christian.koenig@....com> wrote:
>
> Am 01.11.22 um 22:40 schrieb Rob Clark:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > The workaround was initially necessary due to dma_resv having only a
> > single exclusive fence slot, yet whe don't necessarily know what order
> > the gpu scheduler will schedule jobs.  Unfortunately this workaround
> > also has the result of forcing implicit sync, even when userspace does
> > not want it.
> >
> > However, since commit 047a1b877ed4 ("dma-buf & drm/amdgpu: remove
> > dma_resv workaround") the workaround is no longer needed.  So remove
> > it.  This effectively reverts commit f1b3f696a084 ("drm/msm: Don't
> > break exclusive fence ordering")
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
>
> Oh, yes please. I had that on my todo list for after the initial patch
> had landed, but couldn't find the time to look into it once more.
>
> There was another case with one of the other ARM drivers which could be
> cleaned up now, but I can't find it any more of hand.
>
> Anyway this patch here is Acked-by: Christian König
> <christian.koenig@....com>.

Thanks.. I had a quick look for the other driver but couldn't spot
anything, so perhaps it has already been fixed?

BR,
-R

>
> Regards,
> Christian.
>
> > ---
> >   drivers/gpu/drm/msm/msm_gem_submit.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> > index 5599d93ec0d2..cc48f73adadf 100644
> > --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> > +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> > @@ -334,8 +334,7 @@ static int submit_fence_sync(struct msm_gem_submit *submit, bool no_implicit)
> >               if (ret)
> >                       return ret;
> >
> > -             /* exclusive fences must be ordered */
> > -             if (no_implicit && !write)
> > +             if (no_implicit)
> >                       continue;
> >
> >               ret = drm_sched_job_add_implicit_dependencies(&submit->base,
>