1/*
2 * SPDX-License-Identifier: MIT
3 *
4 * Copyright © 2019 Intel Corporation
5 */
6
7#ifndef _I915_ACTIVE_H_
8#define _I915_ACTIVE_H_
9
10#include <linux/lockdep.h>
11
12#include "i915_active_types.h"
13#include "i915_request.h"
14
15struct i915_request;
16struct intel_engine_cs;
17struct intel_timeline;
18
19/*
20 * We treat requests as fences. This is not be to confused with our
21 * "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
22 * We use the fences to synchronize access from the CPU with activity on the
23 * GPU, for example, we should not rewrite an object's PTE whilst the GPU
24 * is reading them. We also track fences at a higher level to provide
25 * implicit synchronisation around GEM objects, e.g. set-domain will wait
26 * for outstanding GPU rendering before marking the object ready for CPU
27 * access, or a pageflip will wait until the GPU is complete before showing
28 * the frame on the scanout.
29 *
30 * In order to use a fence, the object must track the fence it needs to
31 * serialise with. For example, GEM objects want to track both read and
32 * write access so that we can perform concurrent read operations between
33 * the CPU and GPU engines, as well as waiting for all rendering to
34 * complete, or waiting for the last GPU user of a "fence register". The
35 * object then embeds a #i915_active_fence to track the most recent (in
36 * retirement order) request relevant for the desired mode of access.
37 * The #i915_active_fence is updated with i915_active_fence_set() to
38 * track the most recent fence request, typically this is done as part of
39 * i915_vma_move_to_active().
40 *
41 * When the #i915_active_fence completes (is retired), it will
42 * signal its completion to the owner through a callback as well as mark
43 * itself as idle (i915_active_fence.request == NULL). The owner
44 * can then perform any action, such as delayed freeing of an active
45 * resource including itself.
46 */
47
48void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb);
49
50/**
51 * __i915_active_fence_init - prepares the activity tracker for use
52 * @active: the active tracker
53 * @fence: initial fence to track, can be NULL
54 * @fn: a callback when then the tracker is retired (becomes idle),
55 * can be NULL
56 *
57 * i915_active_fence_init() prepares the embedded @active struct for use as
58 * an activity tracker, that is for tracking the last known active fence
59 * associated with it. When the last fence becomes idle, when it is retired
60 * after completion, the optional callback @func is invoked.
61 */
62static inline void
63__i915_active_fence_init(struct i915_active_fence *active,
64 void *fence,
65 dma_fence_func_t fn)
66{
67 RCU_INIT_POINTER(active->fence, fence);
68 active->cb.func = fn ?: i915_active_noop;
69}
70
71#define INIT_ACTIVE_FENCE(A) \
72 __i915_active_fence_init((A), NULL, NULL)
73
74struct dma_fence *
75__i915_active_fence_set(struct i915_active_fence *active,
76 struct dma_fence *fence);
77
78/**
79 * i915_active_fence_set - updates the tracker to watch the current fence
80 * @active: the active tracker
81 * @rq: the request to watch
82 *
83 * i915_active_fence_set() watches the given @rq for completion. While
84 * that @rq is busy, the @active reports busy. When that @rq is signaled
85 * (or else retired) the @active tracker is updated to report idle.
86 */
87int __must_check
88i915_active_fence_set(struct i915_active_fence *active,
89 struct i915_request *rq);
90/**
91 * i915_active_fence_get - return a reference to the active fence
92 * @active: the active tracker
93 *
94 * i915_active_fence_get() returns a reference to the active fence,
95 * or NULL if the active tracker is idle. The reference is obtained under RCU,
96 * so no locking is required by the caller.
97 *
98 * The reference should be freed with dma_fence_put().
99 */
100static inline struct dma_fence *
101i915_active_fence_get(struct i915_active_fence *active)
102{
103 struct dma_fence *fence;
104
105 rcu_read_lock();
106 fence = dma_fence_get_rcu_safe(fencep: &active->fence);
107 rcu_read_unlock();
108
109 return fence;
110}
111
112/**
113 * i915_active_fence_isset - report whether the active tracker is assigned
114 * @active: the active tracker
115 *
116 * i915_active_fence_isset() returns true if the active tracker is currently
117 * assigned to a fence. Due to the lazy retiring, that fence may be idle
118 * and this may report stale information.
119 */
120static inline bool
121i915_active_fence_isset(const struct i915_active_fence *active)
122{
123 return rcu_access_pointer(active->fence);
124}
125
126/*
127 * GPU activity tracking
128 *
129 * Each set of commands submitted to the GPU compromises a single request that
130 * signals a fence upon completion. struct i915_request combines the
131 * command submission, scheduling and fence signaling roles. If we want to see
132 * if a particular task is complete, we need to grab the fence (struct
133 * i915_request) for that task and check or wait for it to be signaled. More
134 * often though we want to track the status of a bunch of tasks, for example
135 * to wait for the GPU to finish accessing some memory across a variety of
136 * different command pipelines from different clients. We could choose to
137 * track every single request associated with the task, but knowing that
138 * each request belongs to an ordered timeline (later requests within a
139 * timeline must wait for earlier requests), we need only track the
140 * latest request in each timeline to determine the overall status of the
141 * task.
142 *
143 * struct i915_active provides this tracking across timelines. It builds a
144 * composite shared-fence, and is updated as new work is submitted to the task,
145 * forming a snapshot of the current status. It should be embedded into the
146 * different resources that need to track their associated GPU activity to
147 * provide a callback when that GPU activity has ceased, or otherwise to
148 * provide a serialisation point either for request submission or for CPU
149 * synchronisation.
150 */
151
152void __i915_active_init(struct i915_active *ref,
153 int (*active)(struct i915_active *ref),
154 void (*retire)(struct i915_active *ref),
155 unsigned long flags,
156 struct lock_class_key *mkey,
157 struct lock_class_key *wkey);
158
159/* Specialise each class of i915_active to avoid impossible lockdep cycles. */
160#define i915_active_init(ref, active, retire, flags) do { \
161 static struct lock_class_key __mkey; \
162 static struct lock_class_key __wkey; \
163 \
164 __i915_active_init(ref, active, retire, flags, &__mkey, &__wkey); \
165} while (0)
166
167int i915_active_add_request(struct i915_active *ref, struct i915_request *rq);
168
169struct dma_fence *
170i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f);
171
172int __i915_active_wait(struct i915_active *ref, int state);
173static inline int i915_active_wait(struct i915_active *ref)
174{
175 return __i915_active_wait(ref, TASK_INTERRUPTIBLE);
176}
177
178int i915_sw_fence_await_active(struct i915_sw_fence *fence,
179 struct i915_active *ref,
180 unsigned int flags);
181int i915_request_await_active(struct i915_request *rq,
182 struct i915_active *ref,
183 unsigned int flags);
184#define I915_ACTIVE_AWAIT_EXCL BIT(0)
185#define I915_ACTIVE_AWAIT_ACTIVE BIT(1)
186#define I915_ACTIVE_AWAIT_BARRIER BIT(2)
187
188int i915_active_acquire(struct i915_active *ref);
189bool i915_active_acquire_if_busy(struct i915_active *ref);
190
191void i915_active_release(struct i915_active *ref);
192
193static inline void __i915_active_acquire(struct i915_active *ref)
194{
195 GEM_BUG_ON(!atomic_read(&ref->count));
196 atomic_inc(v: &ref->count);
197}
198
199static inline bool
200i915_active_is_idle(const struct i915_active *ref)
201{
202 return !atomic_read(v: &ref->count);
203}
204
205void i915_active_fini(struct i915_active *ref);
206
207int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
208 struct intel_engine_cs *engine);
209void i915_active_acquire_barrier(struct i915_active *ref);
210void i915_request_add_active_barriers(struct i915_request *rq);
211
212void i915_active_print(struct i915_active *ref, struct drm_printer *m);
213void i915_active_unlock_wait(struct i915_active *ref);
214
215struct i915_active *i915_active_create(void);
216struct i915_active *i915_active_get(struct i915_active *ref);
217void i915_active_put(struct i915_active *ref);
218
219static inline int __i915_request_await_exclusive(struct i915_request *rq,
220 struct i915_active *active)
221{
222 struct dma_fence *fence;
223 int err = 0;
224
225 fence = i915_active_fence_get(active: &active->excl);
226 if (fence) {
227 err = i915_request_await_dma_fence(rq, fence);
228 dma_fence_put(fence);
229 }
230
231 return err;
232}
233
234void i915_active_module_exit(void);
235int i915_active_module_init(void);
236
237#endif /* _I915_ACTIVE_H_ */
238