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SubjectRe: [PATCH] drm/sched: Extend the documentation.
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Date
Am 05.04.2018 um 00:32 schrieb Eric Anholt:
> These comments answer all the questions I had for myself when
> implementing a driver using the GPU scheduler.
>
> Signed-off-by: Eric Anholt <eric@anholt.net>

Reviewed-by: Christian König <christian.koenig@amd.com>

Already pushed to amd-staging-drm-next as well.

Thanks,
Christian.

> ---
> 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);
> };
>

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