[PATCH] drm/msm: add trace_dma_fence_emit to msm_gpu_submit

[Chia-I Wu]

On Sat, Apr 9, 2022 at 7:33 AM Christian König <christian.koenig at amd.com> wrote:
>
> Am 08.04.22 um 23:12 schrieb Chia-I Wu:
> > In practice, trace_dma_fence_init is good enough and almost no driver
> > calls trace_dma_fence_emit.  But this is still more correct in theory.
>
> Well, the reason why basically no driver is calling this is because it
> is pretty much deprecated.
Why is it considered deprecated?  trace_dma_fence_{emit,signaled} are
useful to visualize fence timelines.  I am actually less sure about
how trace_dma_fence_{init,destroy} are used.

Is it because trace_dma_fence_init is called automatically, and is
good enough most of the time?

>
> We do have a case in the GPU scheduler where it makes sense to distinct
> between init and emit, but it doesn't really matter for drivers.
virtio also has a case where init and emit can be far apart, when the
host cannot process commands fast enough and there is no space in
virtqueue.

>
> So I'm not sure if it's a good idea to add that here.
>
> Regards,
> Christian.
>
> >
> > Signed-off-by: Chia-I Wu <olvaffe at gmail.com>
> > Cc: Rob Clark <robdclark at chromium.org>
> > ---
> >   drivers/gpu/drm/msm/msm_gpu.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> > index faf0c242874e..a82193f41ea2 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu.c
> > +++ b/drivers/gpu/drm/msm/msm_gpu.c
> > @@ -15,6 +15,7 @@
> >   #include <linux/string_helpers.h>
> >   #include <linux/devcoredump.h>
> >   #include <linux/sched/task.h>
> > +#include <trace/events/dma_fence.h>
> >
> >   /*
> >    * Power Management:
> > @@ -769,6 +770,7 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> >       gpu->active_submits++;
> >       mutex_unlock(&gpu->active_lock);
> >
> > +     trace_dma_fence_emit(submit->hw_fence);
> >       gpu->funcs->submit(gpu, submit);
> >       gpu->cur_ctx_seqno = submit->queue->ctx->seqno;
> >
>