[PATCH 1/2] drm/sched: add DRM_SCHED_FENCE_DONT_PIPELINE flag

[Alex Deucher]

On Tue, Oct 18, 2022 at 11:11 AM Christian König
<christian.koenig at amd.com> wrote:
>
> Gentle ping to others to get this reviewed.
>
> Alex, this is fixing the TLB flush errors and I think we need to get it
> into -fixes ASAP.
>
> Christian.
>
> Am 14.10.22 um 10:15 schrieb Christian König:
> > Setting this flag on a scheduler fence prevents pipelining of jobs
> > depending on this fence. In other words we always insert a full CPU
> > round trip before dependen jobs are pushed to the pipeline.

typo: dependen -> dependent

> >
> > Signed-off-by: Christian König <christian.koenig at amd.com>
> > CC: stable at vger.kernel.org # 5.19+

Please add a link to the bug as well for both patches.  With those
fixed, series is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> > ---
> >   drivers/gpu/drm/scheduler/sched_entity.c | 3 ++-
> >   include/drm/gpu_scheduler.h              | 9 +++++++++
> >   2 files changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> > index 191c56064f19..43d337d8b153 100644
> > --- a/drivers/gpu/drm/scheduler/sched_entity.c
> > +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> > @@ -385,7 +385,8 @@ static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity)
> >       }
> >
> >       s_fence = to_drm_sched_fence(fence);
> > -     if (s_fence && s_fence->sched == sched) {
> > +     if (s_fence && s_fence->sched == sched &&
> > +         !test_bit(DRM_SCHED_FENCE_DONT_PIPELINE, &fence->flags)) {
> >
> >               /*
> >                * Fence is from the same scheduler, only need to wait for
> > diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> > index 0fca8f38bee4..f01d14b231ed 100644
> > --- a/include/drm/gpu_scheduler.h
> > +++ b/include/drm/gpu_scheduler.h
> > @@ -32,6 +32,15 @@
> >
> >   #define MAX_WAIT_SCHED_ENTITY_Q_EMPTY msecs_to_jiffies(1000)
> >
> > +/**
> > + * DRM_SCHED_FENCE_DONT_PIPELINE - Prefent dependency pipelining
> > + *
> > + * Setting this flag on a scheduler fence prevents pipelining of jobs depending
> > + * on this fence. In other words we always insert a full CPU round trip before
> > + * dependen jobs are pushed to the hw queue.
> > + */
> > +#define DRM_SCHED_FENCE_DONT_PIPELINE        DMA_FENCE_FLAG_USER_BITS
> > +
> >   struct drm_gem_object;
> >
> >   struct drm_gpu_scheduler;
>