[PATCH v3 12/13] drm/sched/doc: Add Entity teardown documentaion

[Christian König]

Am 12.09.23 um 04:16 schrieb Matthew Brost:
> Provide documentation to guide in ways to teardown an entity.
>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>   Documentation/gpu/drm-mm.rst             |  6 ++++++
>   drivers/gpu/drm/scheduler/sched_entity.c | 19 +++++++++++++++++++
>   2 files changed, 25 insertions(+)
>
> diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst
> index c19b34b1c0ed..cb4d6097897e 100644
> --- a/Documentation/gpu/drm-mm.rst
> +++ b/Documentation/gpu/drm-mm.rst
> @@ -552,6 +552,12 @@ Overview
>   .. kernel-doc:: drivers/gpu/drm/scheduler/sched_main.c
>      :doc: Overview
>   
> +Entity teardown
> +---------------
> +
> +.. kernel-doc:: drivers/gpu/drm/scheduler/sched_entity.c
> +   :doc: Entity teardown
> +
>   Scheduler Function References
>   -----------------------------
>   
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index 37557fbb96d0..76f3e10218bb 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -21,6 +21,25 @@
>    *
>    */
>   
> +/**
> + * DOC: Entity teardown
> + *
> + * Drivers can teardown down an entity for several reasons. Reasons typically
> + * are a user closes the entity via an IOCTL, the FD associated with the entity
> + * is closed, or the entity encounters an error. The GPU scheduler provides the
> + * basic infrastructure to do this in a few different ways.
> + *
> + * 1. Let the entity run dry (both the pending list and job queue) and then call
> + * drm_sched_entity_fini. The backend can accelerate the process of running dry.
> + * For example set a flag so run_job is a NOP and set the TDR to a low value to
> + * signal all jobs in a timely manner (this example works for
> + * DRM_SCHED_POLICY_SINGLE_ENTITY).

Please note that it is a requirement from the X server that all 
externally visible effects of command submission must still be visible 
even after the fd is closed.

This has given us tons amount of headache and is one of the reasons we 
have the drm_sched_entity_flush() handling in the first place.

As long as you don't care about X server compatibility that shouldn't 
matter to you.

Regards,
Christian.

> + *
> + * 2. Kill the entity directly via drm_sched_entity_flush /
> + * drm_sched_entity_fini ensuring all pending and queued jobs are off the
> + * hardware and signaled.



> + */
> +
>   #include <linux/kthread.h>
>   #include <linux/slab.h>
>   #include <linux/completion.h>