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Date: Wed, 22 Sep 2021 08:01:56 -0700
From: Rob Clark <robdclark@...il.com>
To: Andrey Grodzovsky <andrey.grodzovsky@....com>
Cc: dri-devel <dri-devel@...ts.freedesktop.org>,
"moderated list:DMA BUFFER SHARING FRAMEWORK"
<linaro-mm-sig@...ts.linaro.org>, Daniel Vetter <daniel@...ll.ch>,
Christian König <ckoenig.leichtzumerken@...il.com>,
Michel Dänzer <michel@...nzer.net>,
Pekka Paalanen <ppaalanen@...il.com>,
Rob Clark <robdclark@...omium.org>,
David Airlie <airlied@...ux.ie>,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
Tian Tao <tiantao6@...ilicon.com>,
Steven Price <steven.price@....com>,
Melissa Wen <mwen@...lia.com>,
Luben Tuikov <luben.tuikov@....com>,
Boris Brezillon <boris.brezillon@...labora.com>,
Jack Zhang <Jack.Zhang1@....com>,
open list <linux-kernel@...r.kernel.org>,
"open list:DMA BUFFER SHARING FRAMEWORK"
<linux-media@...r.kernel.org>
Subject: Re: [PATCH v3 4/9] drm/scheduler: Add fence deadline support
On Wed, Sep 22, 2021 at 7:31 AM Andrey Grodzovsky
<andrey.grodzovsky@....com> wrote:
>
>
> On 2021-09-21 11:32 p.m., Rob Clark wrote:
> > On Tue, Sep 21, 2021 at 7:18 PM Andrey Grodzovsky
> > <andrey.grodzovsky@....com> wrote:
> >>
> >> On 2021-09-21 4:47 p.m., Rob Clark wrote:
> >>> On Tue, Sep 21, 2021 at 1:09 PM Andrey Grodzovsky
> >>> <andrey.grodzovsky@....com> wrote:
> >>>> On 2021-09-03 2:47 p.m., Rob Clark wrote:
> >>>>
> >>>>> From: Rob Clark <robdclark@...omium.org>
> >>>>>
> >>>>> As the finished fence is the one that is exposed to userspace, and
> >>>>> therefore the one that other operations, like atomic update, would
> >>>>> block on, we need to propagate the deadline from from the finished
> >>>>> fence to the actual hw fence.
> >>>>>
> >>>>> v2: Split into drm_sched_fence_set_parent() (ckoenig)
> >>>>>
> >>>>> Signed-off-by: Rob Clark <robdclark@...omium.org>
> >>>>> ---
> >>>>> drivers/gpu/drm/scheduler/sched_fence.c | 34 +++++++++++++++++++++++++
> >>>>> drivers/gpu/drm/scheduler/sched_main.c | 2 +-
> >>>>> include/drm/gpu_scheduler.h | 8 ++++++
> >>>>> 3 files changed, 43 insertions(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>> index bcea035cf4c6..4fc41a71d1c7 100644
> >>>>> --- a/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>> +++ b/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>> @@ -128,6 +128,30 @@ static void drm_sched_fence_release_finished(struct dma_fence *f)
> >>>>> dma_fence_put(&fence->scheduled);
> >>>>> }
> >>>>>
> >>>>> +static void drm_sched_fence_set_deadline_finished(struct dma_fence *f,
> >>>>> + ktime_t deadline)
> >>>>> +{
> >>>>> + struct drm_sched_fence *fence = to_drm_sched_fence(f);
> >>>>> + unsigned long flags;
> >>>>> +
> >>>>> + spin_lock_irqsave(&fence->lock, flags);
> >>>>> +
> >>>>> + /* If we already have an earlier deadline, keep it: */
> >>>>> + if (test_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT, &f->flags) &&
> >>>>> + ktime_before(fence->deadline, deadline)) {
> >>>>> + spin_unlock_irqrestore(&fence->lock, flags);
> >>>>> + return;
> >>>>> + }
> >>>>> +
> >>>>> + fence->deadline = deadline;
> >>>>> + set_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT, &f->flags);
> >>>>> +
> >>>>> + spin_unlock_irqrestore(&fence->lock, flags);
> >>>>> +
> >>>>> + if (fence->parent)
> >>>>> + dma_fence_set_deadline(fence->parent, deadline);
> >>>>> +}
> >>>>> +
> >>>>> static const struct dma_fence_ops drm_sched_fence_ops_scheduled = {
> >>>>> .get_driver_name = drm_sched_fence_get_driver_name,
> >>>>> .get_timeline_name = drm_sched_fence_get_timeline_name,
> >>>>> @@ -138,6 +162,7 @@ static const struct dma_fence_ops drm_sched_fence_ops_finished = {
> >>>>> .get_driver_name = drm_sched_fence_get_driver_name,
> >>>>> .get_timeline_name = drm_sched_fence_get_timeline_name,
> >>>>> .release = drm_sched_fence_release_finished,
> >>>>> + .set_deadline = drm_sched_fence_set_deadline_finished,
> >>>>> };
> >>>>>
> >>>>> struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f)
> >>>>> @@ -152,6 +177,15 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f)
> >>>>> }
> >>>>> EXPORT_SYMBOL(to_drm_sched_fence);
> >>>>>
> >>>>> +void drm_sched_fence_set_parent(struct drm_sched_fence *s_fence,
> >>>>> + struct dma_fence *fence)
> >>>>> +{
> >>>>> + s_fence->parent = dma_fence_get(fence);
> >>>>> + if (test_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT,
> >>>>> + &s_fence->finished.flags))
> >>>>> + dma_fence_set_deadline(fence, s_fence->deadline);
> >>>> I believe above you should pass be s_fence->finished to
> >>>> dma_fence_set_deadline
> >>>> instead it fence which is the HW fence itself.
> >>> Hmm, unless this has changed recently with some patches I don't have,
> >>> s_fence->parent is the one signalled by hw, so it is the one we want
> >>> to set the deadline on
> >>>
> >>> BR,
> >>> -R
> >>
> >> No it didn't change. But then when exactly will
> >> drm_sched_fence_set_deadline_finished
> >> execute such that fence->parent != NULL ? In other words, I am not clear
> >> how propagation
> >> happens otherwise - if dma_fence_set_deadline is called with the HW
> >> fence then the assumption
> >> here is that driver provided driver specific
> >> dma_fence_ops.dma_fence_set_deadline callback executes
> >> but I was under impression that drm_sched_fence_set_deadline_finished is
> >> the one that propagates
> >> the deadline to the HW fence's callback and for it to execute
> >> dma_fence_set_deadline needs to be called
> >> with s_fence->finished.
> > Assuming I didn't screw up drm/msm conversion to scheduler,
> > &s_fence->finished is the one that will be returned to userspace.. and
> > later passed back to kernel for atomic commit (or to the compositor).
> > So it is the one that fence->set_deadline() will be called on. But
> > s_fence->parent is the actual hw fence that needs to know about the
> > deadline. Depending on whether or not the job has been written into
> > hw ringbuffer or not, there are two cases:
> >
> > 1) not scheduled yet, s_fence will store the deadline and propagate it
> > later once s_fence->parent is known
>
>
> And by later you mean the call to drm_sched_fence_set_parent
> after HW fence is returned ? If yes I think i get it now.
Yup :-)
BR,
-R
> Andrey
>
>
> > 2) already scheduled, in which case s_fence->finished.set_deadline
> > will propagate it directly to the real fence
> >
> > BR,
> > -R
> >
> >> Andrey
> >>
> >>
> >>
> >>>> Andrey
> >>>>
> >>>>
> >>>>> +}
> >>>>> +
> >>>>> struct drm_sched_fence *drm_sched_fence_alloc(struct drm_sched_entity *entity,
> >>>>> void *owner)
> >>>>> {
> >>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> >>>>> index 595e47ff7d06..27bf0ac0625f 100644
> >>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
> >>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> >>>>> @@ -978,7 +978,7 @@ static int drm_sched_main(void *param)
> >>>>> drm_sched_fence_scheduled(s_fence);
> >>>>>
> >>>>> if (!IS_ERR_OR_NULL(fence)) {
> >>>>> - s_fence->parent = dma_fence_get(fence);
> >>>>> + drm_sched_fence_set_parent(s_fence, fence);
> >>>>> r = dma_fence_add_callback(fence, &sched_job->cb,
> >>>>> drm_sched_job_done_cb);
> >>>>> if (r == -ENOENT)
> >>>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> >>>>> index 7f77a455722c..158ddd662469 100644
> >>>>> --- a/include/drm/gpu_scheduler.h
> >>>>> +++ b/include/drm/gpu_scheduler.h
> >>>>> @@ -238,6 +238,12 @@ struct drm_sched_fence {
> >>>>> */
> >>>>> struct dma_fence finished;
> >>>>>
> >>>>> + /**
> >>>>> + * @deadline: deadline set on &drm_sched_fence.finished which
> >>>>> + * potentially needs to be propagated to &drm_sched_fence.parent
> >>>>> + */
> >>>>> + ktime_t deadline;
> >>>>> +
> >>>>> /**
> >>>>> * @parent: the fence returned by &drm_sched_backend_ops.run_job
> >>>>> * when scheduling the job on hardware. We signal the
> >>>>> @@ -505,6 +511,8 @@ void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
> >>>>> enum drm_sched_priority priority);
> >>>>> bool drm_sched_entity_is_ready(struct drm_sched_entity *entity);
> >>>>>
> >>>>> +void drm_sched_fence_set_parent(struct drm_sched_fence *s_fence,
> >>>>> + struct dma_fence *fence);
> >>>>> struct drm_sched_fence *drm_sched_fence_alloc(
> >>>>> struct drm_sched_entity *s_entity, void *owner);
> >>>>> void drm_sched_fence_init(struct drm_sched_fence *fence,
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