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 15 struct i915_request; 16 struct intel_engine_cs; 17 struct 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 48 void 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 * @func - 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 */ 62 static 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 74 struct 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 */ 87 int __must_check 88 i915_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 */ 100 static inline struct dma_fence * 101 i915_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(&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 */ 120 static inline bool 121 i915_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 */ 151 152 void __i915_active_init(struct i915_active *ref, 153 int (*active)(struct i915_active *ref), 154 void (*retire)(struct i915_active *ref), 155 struct lock_class_key *mkey, 156 struct lock_class_key *wkey); 157 158 /* Specialise each class of i915_active to avoid impossible lockdep cycles. */ 159 #define i915_active_init(ref, active, retire) do { \ 160 static struct lock_class_key __mkey; \ 161 static struct lock_class_key __wkey; \ 162 \ 163 __i915_active_init(ref, active, retire, &__mkey, &__wkey); \ 164 } while (0) 165 166 int i915_active_ref(struct i915_active *ref, 167 struct intel_timeline *tl, 168 struct dma_fence *fence); 169 170 static inline int 171 i915_active_add_request(struct i915_active *ref, struct i915_request *rq) 172 { 173 return i915_active_ref(ref, i915_request_timeline(rq), &rq->fence); 174 } 175 176 void i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f); 177 178 static inline bool i915_active_has_exclusive(struct i915_active *ref) 179 { 180 return rcu_access_pointer(ref->excl.fence); 181 } 182 183 int i915_active_wait(struct i915_active *ref); 184 185 int i915_request_await_active(struct i915_request *rq, struct i915_active *ref); 186 187 int i915_active_acquire(struct i915_active *ref); 188 bool i915_active_acquire_if_busy(struct i915_active *ref); 189 void i915_active_release(struct i915_active *ref); 190 191 static inline bool 192 i915_active_is_idle(const struct i915_active *ref) 193 { 194 return !atomic_read(&ref->count); 195 } 196 197 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) 198 void i915_active_fini(struct i915_active *ref); 199 #else 200 static inline void i915_active_fini(struct i915_active *ref) { } 201 #endif 202 203 int i915_active_acquire_preallocate_barrier(struct i915_active *ref, 204 struct intel_engine_cs *engine); 205 void i915_active_acquire_barrier(struct i915_active *ref); 206 void i915_request_add_active_barriers(struct i915_request *rq); 207 208 void i915_active_print(struct i915_active *ref, struct drm_printer *m); 209 void i915_active_unlock_wait(struct i915_active *ref); 210 211 #endif /* _I915_ACTIVE_H_ */ 212