Re: [PATCH] drm/sched: Call drm_sched_fence_set_parent() from drm_sched_fence_scheduled()

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue, 13 Jun 2023 11:44:24 +0200
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> Drivers that can delegate waits to the firmware/GPU pass the scheduled
> fence to drm_sched_job_add_dependency(), and issue wait commands to
> the firmware/GPU at job submission time. For this to be possible, they
> need all their 'native' dependencies to have a valid parent since this
> is where the actual HW fence information are encoded.
> 
> In drm_sched_main(), we currently call drm_sched_fence_set_parent()
> after drm_sched_fence_set_parent(), leaving a short period of time

after drm_sched_fence_scheduled(), ...

> during which the job depending on this fence can be submitted.
> 
> Since setting parent and signaling the fence are two things that are
> kinda related (you can't have a parent if the job hasn't been scheduled),
> it probably makes sense to pass the parent fence to
> drm_sched_fence_scheduled() and let it call drm_sched_fence_set_parent()
> before it signals the scheduled fence.