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@xxxxxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx> 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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