drm/sched: Replacement for drm_sched_resubmit_jobs() is deprecated

[Boris Brezillon]

Hello Christian, Alex,

As part of our transition to drm_sched for the powervr GPU driver, we
realized drm_sched_resubmit_jobs(), which is used by all drivers
relying on drm_sched right except amdgpu, has been deprecated.
Unfortunately, commit 5efbe6aa7a0e ("drm/scheduler: deprecate
drm_sched_resubmit_jobs") doesn't describe what drivers should do or use
as an alternative.

At the very least, for our implementation, we need to restore the
drm_sched_job::parent pointers that were set to NULL in
drm_sched_stop(), such that jobs submitted before the GPU recovery are
considered active when drm_sched_start() is called. That could be done
with a custom pending_list iteration restoring drm_sched_job::parent's
pointer, but that seems odd to let the scheduler backend manipulate
this list directly, and I suspect we need to do other checks, like the
karma vs hang-limit thing, so we can flag the entity dirty and cancel
all jobs being queued there if the entity has caused too many hangs.

Now that drm_sched_resubmit_jobs() has been deprecated, that would be
great if you could help us write a piece of documentation describing
what should be done between drm_sched_stop() and drm_sched_start(), so
new drivers don't come up with their own slightly different/broken
version of the same thing.

Thanks in advance for your help.

Regards,

Boris