1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2018 Intel Corporation
5  */
6 
7 #ifndef _I915_SCHEDULER_H_
8 #define _I915_SCHEDULER_H_
9 
10 #include <linux/bitops.h>
11 
12 #include <uapi/drm/i915_drm.h>
13 
14 enum {
15 	I915_PRIORITY_MIN = I915_CONTEXT_MIN_USER_PRIORITY - 1,
16 	I915_PRIORITY_NORMAL = I915_CONTEXT_DEFAULT_PRIORITY,
17 	I915_PRIORITY_MAX = I915_CONTEXT_MAX_USER_PRIORITY + 1,
18 
19 	I915_PRIORITY_INVALID = INT_MIN
20 };
21 
22 struct i915_sched_attr {
23 	/**
24 	 * @priority: execution and service priority
25 	 *
26 	 * All clients are equal, but some are more equal than others!
27 	 *
28 	 * Requests from a context with a greater (more positive) value of
29 	 * @priority will be executed before those with a lower @priority
30 	 * value, forming a simple QoS.
31 	 *
32 	 * The &drm_i915_private.kernel_context is assigned the lowest priority.
33 	 */
34 	int priority;
35 };
36 
37 /*
38  * "People assume that time is a strict progression of cause to effect, but
39  * actually, from a nonlinear, non-subjective viewpoint, it's more like a big
40  * ball of wibbly-wobbly, timey-wimey ... stuff." -The Doctor, 2015
41  *
42  * Requests exist in a complex web of interdependencies. Each request
43  * has to wait for some other request to complete before it is ready to be run
44  * (e.g. we have to wait until the pixels have been rendering into a texture
45  * before we can copy from it). We track the readiness of a request in terms
46  * of fences, but we also need to keep the dependency tree for the lifetime
47  * of the request (beyond the life of an individual fence). We use the tree
48  * at various points to reorder the requests whilst keeping the requests
49  * in order with respect to their various dependencies.
50  *
51  * There is no active component to the "scheduler". As we know the dependency
52  * DAG of each request, we are able to insert it into a sorted queue when it
53  * is ready, and are able to reorder its portion of the graph to accommodate
54  * dynamic priority changes.
55  */
56 struct i915_sched_node {
57 	struct list_head signalers_list; /* those before us, we depend upon */
58 	struct list_head waiters_list; /* those after us, they depend upon us */
59 	struct list_head link;
60 	struct i915_sched_attr attr;
61 };
62 
63 struct i915_dependency {
64 	struct i915_sched_node *signaler;
65 	struct list_head signal_link;
66 	struct list_head wait_link;
67 	struct list_head dfs_link;
68 	unsigned long flags;
69 #define I915_DEPENDENCY_ALLOC BIT(0)
70 };
71 
72 #endif /* _I915_SCHEDULER_H_ */
73