drivers/gpu/drm/i915/i915_active.h

   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_ */