path: root/drivers/gpu/drm/scheduler/sched_main.c

/*
 * Copyright 2015 Advanced Micro Devices, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 */

/**
 * DOC: Overview
 *
 * The GPU scheduler provides entities which allow userspace to push jobs
 * into software queues which are then scheduled on a hardware run queue.
 * The software queues have a priority among them. The scheduler selects the entities
 * from the run queue using a FIFO. The scheduler provides dependency handling
 * features among jobs. The driver is supposed to provide callback functions for
 * backend operations to the scheduler like submitting a job to hardware run queue,
 * returning the dependencies of a job etc.
 *
 * The organisation of the scheduler is the following:
 *
 * 1. Each hw run queue has one scheduler
 * 2. Each scheduler has multiple run queues with different priorities
 *    (e.g., HIGH_HW,HIGH_SW, KERNEL, NORMAL)
 * 3. Each scheduler run queue has a queue of entities to schedule
 * 4. Entities themselves maintain a queue of jobs that will be scheduled on
 *    the hardware.
 *
 * The jobs in a entity are always scheduled in the order that they were pushed.
 */

#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/dma-resv.h>
#include <uapi/linux/sched/types.h>

#include <drm/drm_print.h>
#include <drm/drm_gem.h>
#include <drm/gpu_scheduler.h>
#include <drm/spsc_queue.h>

#define CREATE_TRACE_POINTS
#include "gpu_scheduler_trace.h"

#define to_drm_sched_job(sched_job)		\
		container_of((sched_job), struct drm_sched_job, queue_node)

/**
 * drm_sched_rq_init - initialize a given run queue struct
 *
 * @sched: scheduler instance to associate with this run queue
 * @rq: scheduler run queue
 *
 * Initializes a scheduler runqueue.
 */
static void drm_sched_rq_init(struct drm_gpu_scheduler *sched,
			      struct drm_sched_rq *rq)
{
	spin_lock_init(&rq->lock);
	INIT_LIST_HEAD(&rq->entities);
	rq->current_entity = NULL;
	rq->sched = sched;
}

/**
 * drm_sched_rq_add_entity - add an entity
 *
 * @rq: scheduler run queue
 * @entity: scheduler entity
 *
 * Adds a scheduler entity to the run queue.
 */
void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
			     struct drm_sched_entity *entity)
{
	if (!list_empty(&entity->list))
		return;
	spin_lock(&rq->lock);
	atomic_inc(rq->sched->score);
	list_add_tail(&entity->list, &rq->entities);
	spin_unlock(&rq->lock);
}

/**
 * drm_sched_rq_remove_entity - remove an entity
 *
 * @rq: scheduler run queue
 * @entity: scheduler entity
 *
 * Removes a scheduler entity from the run queue.
 */
void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
				struct drm_sched_entity *entity)
{
	if (list_empty(&entity->list))
		return;
	spin_lock(&rq->lock);
	atomic_dec(rq->sched->score);
	list_del_init(&entity->list);
	if (rq->current_entity == entity)
		rq->current_entity = NULL;
	spin_unlock(&rq->lock);
}

/**
 * drm_sched_rq_select_entity - Select an entity which could provide a job to run
 *
 * @rq: scheduler run queue to check.
 *
 * Try to find a ready entity, returns NULL if none found.
 */
static struct drm_sched_entity *
drm_sched_rq_select_entity(struct drm_sched_rq *rq)
{
	struct drm_sched_entity *entity;

	spin_lock(&rq->lock);

	entity = rq->current_entity;
	if (entity) {
		list_for_each_entry_continue(entity, &rq->entities, list) {
			if (drm_sched_entity_is_ready(entity)) {
				rq->current_entity = entity;
				reinit_completion(&entity->entity_idle);
				spin_unlock(&rq->lock);
				return entity;
			}
		}
	}

	list_for_each_entry(entity, &rq->entities, list) {

		if (drm_sched_entity_is_ready(entity)) {
			rq->current_entity = entity;
			reinit_completion(&entity->entity_idle);
			spin_unlock(&rq->lock);
			return entity;
		}

		if (entity == rq->current_entity)
			break;
	}

	spin_unlock(&rq->lock);

	return NULL;
}

/**
 * drm_sched_job_done - complete a job
 * @s_job: pointer to the job which is done
 *
 * Finish the job's fence and wake up the worker thread.
 */
static void drm_sched_job_done(struct drm_sched_job *s_job)
{
	struct drm_sched_fence *s_fence = s_job->s_fence;
	struct drm_gpu_scheduler *sched = s_fence->sched;

	atomic_dec(&sched->hw_rq_count);
	atomic_dec(sched->score);

	trace_drm_sched_process_job(s_fence);

	dma_fence_get(&s_fence->finished);
	drm_sched_fence_finished(s_fence);
	dma_fence_put(&s_fence->finished);
	wake_up_interruptible(&sched->wake_up_worker