[PATCH] drm/sched: Extend the documentation.

[Alex Deucher]

On Thu, Apr 5, 2018 at 2:16 AM, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Thu, Apr 5, 2018 at 12:32 AM, Eric Anholt <eric at anholt.net> wrote:
>> These comments answer all the questions I had for myself when
>> implementing a driver using the GPU scheduler.
>>
>> Signed-off-by: Eric Anholt <eric at anholt.net>
>
> Pulling all these comments into the generated kerneldoc would be
> awesome, maybe as a new "GPU Scheduler" chapter at the end of
> drm-mm.rst? Would mean a bit of busywork to convert the existing raw
> comments into proper kerneldoc. Also has the benefit that 0day will
> complain when you forget to update the comment when editing the
> function prototype - kerneldoc which isn't included anywhere in .rst
> won't be checked automatically.

I was actually planning to do this myself, but Nayan wanted to do this
a prep work for his proposed GSoC project so I was going to see how
far he got first.

Alex

> -Daniel
>
>> ---
>>  include/drm/gpu_scheduler.h | 46 +++++++++++++++++++++++++++++++++----
>>  1 file changed, 42 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>> index dfd54fb94e10..c053a32341bf 100644
>> --- a/include/drm/gpu_scheduler.h
>> +++ b/include/drm/gpu_scheduler.h
>> @@ -43,10 +43,12 @@ enum drm_sched_priority {
>>  };
>>
>>  /**
>> - * A scheduler entity is a wrapper around a job queue or a group
>> - * of other entities. Entities take turns emitting jobs from their
>> - * job queues to corresponding hardware ring based on scheduling
>> - * policy.
>> + * drm_sched_entity - A wrapper around a job queue (typically attached
>> + * to the DRM file_priv).
>> + *
>> + * Entities will emit jobs in order to their corresponding hardware
>> + * ring, and the scheduler will alternate between entities based on
>> + * scheduling policy.
>>  */
>>  struct drm_sched_entity {
>>         struct list_head                list;
>> @@ -78,7 +80,18 @@ struct drm_sched_rq {
>>
>>  struct drm_sched_fence {
>>         struct dma_fence                scheduled;
>> +
>> +       /* This fence is what will be signaled by the scheduler when
>> +        * the job is completed.
>> +        *
>> +        * When setting up an out fence for the job, you should use
>> +        * this, since it's available immediately upon
>> +        * drm_sched_job_init(), and the fence returned by the driver
>> +        * from run_job() won't be created until the dependencies have
>> +        * resolved.
>> +        */
>>         struct dma_fence                finished;
>> +
>>         struct dma_fence_cb             cb;
>>         struct dma_fence                *parent;
>>         struct drm_gpu_scheduler        *sched;
>> @@ -88,6 +101,13 @@ struct drm_sched_fence {
>>
>>  struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>>
>> +/**
>> + * drm_sched_job - A job to be run by an entity.
>> + *
>> + * A job is created by the driver using drm_sched_job_init(), and
>> + * should call drm_sched_entity_push_job() once it wants the scheduler
>> + * to schedule the job.
>> + */
>>  struct drm_sched_job {
>>         struct spsc_node                queue_node;
>>         struct drm_gpu_scheduler        *sched;
>> @@ -112,10 +132,28 @@ static inline bool drm_sched_invalidate_job(struct drm_sched_job *s_job,
>>   * these functions should be implemented in driver side
>>  */
>>  struct drm_sched_backend_ops {
>> +       /* Called when the scheduler is considering scheduling this
>> +        * job next, to get another struct dma_fence for this job to
>> +        * block on.  Once it returns NULL, run_job() may be called.
>> +        */
>>         struct dma_fence *(*dependency)(struct drm_sched_job *sched_job,
>>                                         struct drm_sched_entity *s_entity);
>> +
>> +       /* Called to execute the job once all of the dependencies have
>> +        * been resolved.  This may be called multiple times, if
>> +        * timedout_job() has happened and drm_sched_job_recovery()
>> +        * decides to try it again.
>> +        */
>>         struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
>> +
>> +       /* Called when a job has taken too long to execute, to trigger
>> +        * GPU recovery.
>> +        */
>>         void (*timedout_job)(struct drm_sched_job *sched_job);
>> +
>> +       /* Called once the job's finished fence has been signaled and
>> +        * it's time to clean it up.
>> +        */
>>         void (*free_job)(struct drm_sched_job *sched_job);
>>  };
>>
>> --
>> 2.17.0
>>
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>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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