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From:   Rob Clark <robdclark@gmail.com>
Date:   Tue, 20 Jul 2021 11:30:53 -0700
Message-ID: <CAF6AEGtOW3EjZWo36ij8U1om=gAqvg8CSkJJq2GkyHFGWUH4kQ@mail.gmail.com>
Subject: Re: [Linaro-mm-sig] [PATCH] drm/msm: Add fence->wait() op
To:     =?UTF-8?Q?Christian_K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>
Cc:     dri-devel <dri-devel@lists.freedesktop.org>,
        Rob Clark <robdclark@chromium.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@lists.freedesktop.org>, David Airlie <airlied@linux.ie>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@lists.linaro.org>, Daniel Vetter <daniel@ffwll.ch>,
        Sean Paul <sean@poorly.run>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@vger.kernel.org>
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On Tue, Jul 20, 2021 at 11:03 AM Christian K=C3=B6nig
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> Hi Rob,
>
> Am 20.07.21 um 17:07 schrieb Rob Clark:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > Somehow we had neither ->wait() nor dma_fence_signal() calls, and no
> > one noticed.  Oops.
>
>
> I'm not sure if that is a good idea.
>
> The dma_fence->wait() callback is pretty much deprecated and should not
> be used any more.
>
> What exactly do you need that for?

Well, the alternative is to track the set of fences which have
signalling enabled, and then figure out which ones to signal, which
seems like a lot more work, vs just re-purposing the wait
implementation we already have for non-dma_fence cases ;-)

Why is the ->wait() callback (pretty much) deprecated?

BR,
-R

> Regards,
> Christian.
>
> >
> > Note that this removes the !timeout case, which has not been used in
> > a long time.
>
>
> >
> > Signed-off-by: Rob Clark <robdclark@chromium.org>
> > ---
> >   drivers/gpu/drm/msm/msm_fence.c | 59 +++++++++++++++++++-------------=
-
> >   1 file changed, 34 insertions(+), 25 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_=
fence.c
> > index cd59a5918038..8ee96b90ded6 100644
> > --- a/drivers/gpu/drm/msm/msm_fence.c
> > +++ b/drivers/gpu/drm/msm/msm_fence.c
> > @@ -38,11 +38,10 @@ static inline bool fence_completed(struct msm_fence=
_context *fctx, uint32_t fenc
> >       return (int32_t)(fctx->completed_fence - fence) >=3D 0;
> >   }
> >
> > -/* legacy path for WAIT_FENCE ioctl: */
> > -int msm_wait_fence(struct msm_fence_context *fctx, uint32_t fence,
> > -             ktime_t *timeout, bool interruptible)
> > +static signed long wait_fence(struct msm_fence_context *fctx, uint32_t=
 fence,
> > +             signed long remaining_jiffies, bool interruptible)
> >   {
> > -     int ret;
> > +     signed long ret;
> >
> >       if (fence > fctx->last_fence) {
> >               DRM_ERROR_RATELIMITED("%s: waiting on invalid fence: %u (=
of %u)\n",
> > @@ -50,33 +49,34 @@ int msm_wait_fence(struct msm_fence_context *fctx, =
uint32_t fence,
> >               return -EINVAL;
> >       }
> >
> > -     if (!timeout) {
> > -             /* no-wait: */
> > -             ret =3D fence_completed(fctx, fence) ? 0 : -EBUSY;
> > +     if (interruptible) {
> > +             ret =3D wait_event_interruptible_timeout(fctx->event,
> > +                     fence_completed(fctx, fence),
> > +                     remaining_jiffies);
> >       } else {
> > -             unsigned long remaining_jiffies =3D timeout_to_jiffies(ti=
meout);
> > -
> > -             if (interruptible)
> > -                     ret =3D wait_event_interruptible_timeout(fctx->ev=
ent,
> > -                             fence_completed(fctx, fence),
> > -                             remaining_jiffies);
> > -             else
> > -                     ret =3D wait_event_timeout(fctx->event,
> > -                             fence_completed(fctx, fence),
> > -                             remaining_jiffies);
> > -
> > -             if (ret =3D=3D 0) {
> > -                     DBG("timeout waiting for fence: %u (completed: %u=
)",
> > -                                     fence, fctx->completed_fence);
> > -                     ret =3D -ETIMEDOUT;
> > -             } else if (ret !=3D -ERESTARTSYS) {
> > -                     ret =3D 0;
> > -             }
> > +             ret =3D wait_event_timeout(fctx->event,
> > +                     fence_completed(fctx, fence),
> > +                     remaining_jiffies);
> > +     }
> > +
> > +     if (ret =3D=3D 0) {
> > +             DBG("timeout waiting for fence: %u (completed: %u)",
> > +                             fence, fctx->completed_fence);
> > +             ret =3D -ETIMEDOUT;
> > +     } else if (ret !=3D -ERESTARTSYS) {
> > +             ret =3D 0;
> >       }
> >
> >       return ret;
> >   }
> >
> > +/* legacy path for WAIT_FENCE ioctl: */
> > +int msm_wait_fence(struct msm_fence_context *fctx, uint32_t fence,
> > +             ktime_t *timeout, bool interruptible)
> > +{
> > +     return wait_fence(fctx, fence, timeout_to_jiffies(timeout), inter=
ruptible);
> > +}
> > +
> >   /* called from workqueue */
> >   void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence)
> >   {
> > @@ -114,10 +114,19 @@ static bool msm_fence_signaled(struct dma_fence *=
fence)
> >       return fence_completed(f->fctx, f->base.seqno);
> >   }
> >
> > +static signed long msm_fence_wait(struct dma_fence *fence, bool intr,
> > +             signed long timeout)
> > +{
> > +     struct msm_fence *f =3D to_msm_fence(fence);
> > +
> > +     return wait_fence(f->fctx, fence->seqno, timeout, intr);
> > +}
> > +
> >   static const struct dma_fence_ops msm_fence_ops =3D {
> >       .get_driver_name =3D msm_fence_get_driver_name,
> >       .get_timeline_name =3D msm_fence_get_timeline_name,
> >       .signaled =3D msm_fence_signaled,
> > +     .wait =3D msm_fence_wait,
> >   };
> >
> >   struct dma_fence *
>