Re: [PATCH v2] drm/amdgpu: set start timestamp of fence in the right place

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 10.07.24 um 09:54 schrieb Zhu, Jiadong:
> [AMD Official Use Only - AMD Internal Distribution Only]
>
> > -----Original Message-----
> > From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
> > Sent: Wednesday, July 10, 2024 3:17 PM
> > To: Zhu, Jiadong <Jiadong.Zhu@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v2] drm/amdgpu: set start timestamp of fence in the
> > right place
> >
> > Am 10.07.24 um 02:31 schrieb jiadong.zhu@xxxxxxx:
> > > From: Jiadong Zhu <Jiadong.Zhu@xxxxxxx>
> > >
> > > The job's embedded fence is dma_fence which shall not be conversed to
> > > amdgpu_fence.
> > Good catch.
> >
> > > The start timestamp shall be saved on job for hw_fence.
> > But NAK to that approach. Why do we need the start time here in the first
> > place?
> >
> > Regards,
> > Christian.
> The start timestamp is used for ring mux to check if the fences are  unsignaled for a period of time under mcbp scenarios (by calling amdgpu_fence_last_unsignaled_time_us).

I can't find a reason for doing that in the first place. What is the 
background of this?

Regards,
Christian.


> Thanks,
> Jiadong
> > > v2: optimize get_fence_start_time.
> > > Signed-off-by: Jiadong Zhu <Jiadong.Zhu@xxxxxxx>
> > > ---
> > >    drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 31
> > ++++++++++++++++++++---
> > >    drivers/gpu/drm/amd/amdgpu/amdgpu_job.h   |  3 +++
> > >    2 files changed, 31 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > index 2f24a6aa13bf..72bb007e48c8 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > @@ -88,6 +88,31 @@ static inline struct amdgpu_fence
> > *to_amdgpu_fence(struct dma_fence *f)
> > >      return NULL;
> > >    }
> > >
> > > +static inline void set_fence_start_time(struct dma_fence *f, ktime_t
> > > +start_timestamp) {
> > > +   if (f->ops == &amdgpu_fence_ops) {
> > > +           struct amdgpu_fence *__f = container_of(f, struct
> > amdgpu_fence,
> > > +base);
> > > +
> > > +           __f->start_timestamp = start_timestamp;
> > > +   } else if (f->ops == &amdgpu_job_fence_ops) {
> > > +           struct amdgpu_job *job = container_of(f, struct amdgpu_job,
> > > +hw_fence);
> > > +
> > > +           job->start_timestamp = start_timestamp;
> > > +   }
> > > +}
> > > +
> > > +static inline ktime_t get_fence_start_time(struct dma_fence *f) {
> > > +   if (unlikely(f->ops == &amdgpu_fence_ops)) {
> > > +           struct amdgpu_fence *__f = container_of(f, struct
> > amdgpu_fence,
> > > +base);
> > > +
> > > +           return __f->start_timestamp;
> > > +   }
> > > +   struct amdgpu_job *job = container_of(f, struct amdgpu_job,
> > > +hw_fence);
> > > +
> > > +   return job->start_timestamp;
> > > +}
> > > +
> > >    /**
> > >     * amdgpu_fence_write - write a fence value
> > >     *
> > > @@ -197,7 +222,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring,
> > struct dma_fence **f, struct amd
> > >              }
> > >      }
> > >
> > > -   to_amdgpu_fence(fence)->start_timestamp = ktime_get();
> > > +   set_fence_start_time(fence, ktime_get());
> > >
> > >      /* This function can't be called concurrently anyway, otherwise
> > >       * emitting the fence would mess up the hardware ring buffer.
> > > @@ -428,7 +453,7 @@ u64
> > amdgpu_fence_last_unsignaled_time_us(struct amdgpu_ring *ring)
> > >              return 0;
> > >
> > >      return ktime_us_delta(ktime_get(),
> > > -           to_amdgpu_fence(fence)->start_timestamp);
> > > +           get_fence_start_time(fence));
> > >    }
> > >
> > >    /**
> > > @@ -451,7 +476,7 @@ void
> > amdgpu_fence_update_start_timestamp(struct amdgpu_ring *ring,
> > uint32_t seq,
> > >      if (!fence)
> > >              return;
> > >
> > > -   to_amdgpu_fence(fence)->start_timestamp = timestamp;
> > > +   set_fence_start_time(fence, timestamp);
> > >    }
> > >
> > >    /**
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
> > > b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
> > > index a963a25ddd62..3a73fe11a1ce 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
> > > @@ -73,6 +73,9 @@ struct amdgpu_job {
> > >      uint64_t                gds_va;
> > >      bool                    init_shadow;
> > >
> > > +   /* start timestamp for hw_fence*/
> > > +   ktime_t                 start_timestamp;
> > > +
> > >      /* job_run_counter >= 1 means a resubmit job */
> > >      uint32_t                job_run_counter;