drivers/gpu/drm/i915/i915_scheduler.h

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2018 Intel Corporation
 */

#ifndef _I915_SCHEDULER_H_
#define _I915_SCHEDULER_H_

#include <linux/bitops.h>
#include <linux/list.h>
#include <linux/kernel.h>

#include "i915_scheduler_types.h"

#define priolist_for_each_request(it, plist, idx) \
	for (idx = 0; idx < ARRAY_SIZE((plist)->requests); idx++) \
		list_for_each_entry(it, &(plist)->requests[idx], sched.link)

#define priolist_for_each_request_consume(it, n, plist, idx) \
	for (; \
	     (plist)->used ? (idx = __ffs((plist)->used)), 1 : 0; \
	     (plist)->used &= ~BIT(idx)) \
		list_for_each_entry_safe(it, n, \
					 &(plist)->requests[idx], \
					 sched.link)

void i915_sched_node_init(struct i915_sched_node *node);

bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
				      struct i915_sched_node *signal,
				      struct i915_dependency *dep,
				      unsigned long flags);

int i915_sched_node_add_dependency(struct i915_sched_node *node,
				   struct i915_sched_node *signal);

void i915_sched_node_fini(struct i915_sched_node *node);

void i915_schedule(struct i915_request *request,
		   const struct i915_sched_attr *attr);

void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump);

struct list_head *
i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio);

void __i915_priolist_free(struct i915_priolist *p);
static inline void i915_priolist_free(struct i915_priolist *p)
{
	if (p->priority != I915_PRIORITY_NORMAL)
		__i915_priolist_free(p);
}

static inline bool i915_scheduler_need_preempt(int prio, int active)
{
	/*
	 * Allow preemption of low -> normal -> high, but we do
	 * not allow low priority tasks to preempt other low priority
	 * tasks under the impression that latency for low priority
	 * tasks does not matter (as much as background throughput),
	 * so kiss.
	 *
	 * More naturally we would write
	 *	prio >= max(0, last);
	 * except that we wish to prevent triggering preemption at the same
	 * priority level: the task that is running should remain running
	 * to preserve FIFO ordering of dependencies.
	 */
	return prio > max(I915_PRIORITY_NORMAL - 1, active);
}

#endif /* _I915_SCHEDULER_H_ */