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25 #include <linux/prefetch.h>
29 static const char *i915_fence_get_driver_name(struct fence *fence)
34 static const char *i915_fence_get_timeline_name(struct fence *fence)
36 /* Timelines are bound by eviction to a VM. However, since
37 * we only have a global seqno at the moment, we only have
38 * a single timeline. Note that each timeline will have
39 * multiple execution contexts (fence contexts) as we allow
40 * engines within a single timeline to execute in parallel.
45 static bool i915_fence_signaled(struct fence *fence)
47 return i915_gem_request_completed(to_request(fence));
50 static bool i915_fence_enable_signaling(struct fence *fence)
52 if (i915_fence_signaled(fence))
55 intel_engine_enable_signaling(to_request(fence));
59 static signed long i915_fence_wait(struct fence *fence,
61 signed long timeout_jiffies)
63 s64 timeout_ns, *timeout;
66 if (timeout_jiffies != MAX_SCHEDULE_TIMEOUT) {
67 timeout_ns = jiffies_to_nsecs(timeout_jiffies);
68 timeout = &timeout_ns;
73 ret = i915_wait_request(to_request(fence),
74 interruptible, timeout,
82 if (timeout_jiffies != MAX_SCHEDULE_TIMEOUT)
83 timeout_jiffies = nsecs_to_jiffies(timeout_ns);
85 return timeout_jiffies;
88 static void i915_fence_value_str(struct fence *fence, char *str, int size)
90 snprintf(str, size, "%u", fence->seqno);
93 static void i915_fence_timeline_value_str(struct fence *fence, char *str,
96 snprintf(str, size, "%u",
97 intel_engine_get_seqno(to_request(fence)->engine));
100 static void i915_fence_release(struct fence *fence)
102 struct drm_i915_gem_request *req = to_request(fence);
104 kmem_cache_free(req->i915->requests, req);
107 const struct fence_ops i915_fence_ops = {
108 .get_driver_name = i915_fence_get_driver_name,
109 .get_timeline_name = i915_fence_get_timeline_name,
110 .enable_signaling = i915_fence_enable_signaling,
111 .signaled = i915_fence_signaled,
112 .wait = i915_fence_wait,
113 .release = i915_fence_release,
114 .fence_value_str = i915_fence_value_str,
115 .timeline_value_str = i915_fence_timeline_value_str,
118 int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
119 struct drm_file *file)
121 struct drm_i915_private *dev_private;
122 struct drm_i915_file_private *file_priv;
124 WARN_ON(!req || !file || req->file_priv);
132 dev_private = req->i915;
133 file_priv = file->driver_priv;
135 spin_lock(&file_priv->mm.lock);
136 req->file_priv = file_priv;
137 list_add_tail(&req->client_list, &file_priv->mm.request_list);
138 spin_unlock(&file_priv->mm.lock);
144 i915_gem_request_remove_from_client(struct drm_i915_gem_request *request)
146 struct drm_i915_file_private *file_priv = request->file_priv;
151 spin_lock(&file_priv->mm.lock);
152 list_del(&request->client_list);
153 request->file_priv = NULL;
154 spin_unlock(&file_priv->mm.lock);
157 void i915_gem_retire_noop(struct i915_gem_active *active,
158 struct drm_i915_gem_request *request)
160 /* Space left intentionally blank */
163 static void i915_gem_request_retire(struct drm_i915_gem_request *request)
165 struct i915_gem_active *active, *next;
167 trace_i915_gem_request_retire(request);
168 list_del(&request->link);
170 /* We know the GPU must have read the request to have
171 * sent us the seqno + interrupt, so use the position
172 * of tail of the request to update the last known position
175 * Note this requires that we are always called in request
178 list_del(&request->ring_link);
179 request->ring->last_retired_head = request->postfix;
181 /* Walk through the active list, calling retire on each. This allows
182 * objects to track their GPU activity and mark themselves as idle
183 * when their *last* active request is completed (updating state
184 * tracking lists for eviction, active references for GEM, etc).
186 * As the ->retire() may free the node, we decouple it first and
187 * pass along the auxiliary information (to avoid dereferencing
188 * the node after the callback).
190 list_for_each_entry_safe(active, next, &request->active_list, link) {
191 /* In microbenchmarks or focusing upon time inside the kernel,
192 * we may spend an inordinate amount of time simply handling
193 * the retirement of requests and processing their callbacks.
194 * Of which, this loop itself is particularly hot due to the
195 * cache misses when jumping around the list of i915_gem_active.
196 * So we try to keep this loop as streamlined as possible and
197 * also prefetch the next i915_gem_active to try and hide
198 * the likely cache miss.
202 INIT_LIST_HEAD(&active->link);
203 RCU_INIT_POINTER(active->request, NULL);
205 active->retire(active, request);
208 i915_gem_request_remove_from_client(request);
210 if (request->previous_context) {
211 if (i915.enable_execlists)
212 intel_lr_context_unpin(request->previous_context,
216 i915_gem_context_put(request->ctx);
217 i915_gem_request_put(request);
220 void i915_gem_request_retire_upto(struct drm_i915_gem_request *req)
222 struct intel_engine_cs *engine = req->engine;
223 struct drm_i915_gem_request *tmp;
225 lockdep_assert_held(&req->i915->drm.struct_mutex);
226 GEM_BUG_ON(list_empty(&req->link));
229 tmp = list_first_entry(&engine->request_list,
232 i915_gem_request_retire(tmp);
233 } while (tmp != req);
236 static int i915_gem_check_wedge(unsigned int reset_counter, bool interruptible)
238 if (__i915_terminally_wedged(reset_counter))
241 if (__i915_reset_in_progress(reset_counter)) {
242 /* Non-interruptible callers can't handle -EAGAIN, hence return
243 * -EIO unconditionally for these.
254 static int i915_gem_init_seqno(struct drm_i915_private *dev_priv, u32 seqno)
256 struct intel_engine_cs *engine;
259 /* Carefully retire all requests without writing to the rings */
260 for_each_engine(engine, dev_priv) {
261 ret = intel_engine_idle(engine, true);
265 i915_gem_retire_requests(dev_priv);
267 /* If the seqno wraps around, we need to clear the breadcrumb rbtree */
268 if (!i915_seqno_passed(seqno, dev_priv->next_seqno)) {
269 while (intel_kick_waiters(dev_priv) ||
270 intel_kick_signalers(dev_priv))
274 /* Finally reset hw state */
275 for_each_engine(engine, dev_priv)
276 intel_engine_init_seqno(engine, seqno);
281 int i915_gem_set_seqno(struct drm_device *dev, u32 seqno)
283 struct drm_i915_private *dev_priv = to_i915(dev);
289 /* HWS page needs to be set less than what we
290 * will inject to ring
292 ret = i915_gem_init_seqno(dev_priv, seqno - 1);
296 dev_priv->next_seqno = seqno;
300 static int i915_gem_get_seqno(struct drm_i915_private *dev_priv, u32 *seqno)
302 /* reserve 0 for non-seqno */
303 if (unlikely(dev_priv->next_seqno == 0)) {
306 ret = i915_gem_init_seqno(dev_priv, 0);
310 dev_priv->next_seqno = 1;
313 *seqno = dev_priv->next_seqno++;
318 * i915_gem_request_alloc - allocate a request structure
320 * @engine: engine that we wish to issue the request on.
321 * @ctx: context that the request will be associated with.
322 * This can be NULL if the request is not directly related to
323 * any specific user context, in which case this function will
324 * choose an appropriate context to use.
326 * Returns a pointer to the allocated request if successful,
327 * or an error code if not.
329 struct drm_i915_gem_request *
330 i915_gem_request_alloc(struct intel_engine_cs *engine,
331 struct i915_gem_context *ctx)
333 struct drm_i915_private *dev_priv = engine->i915;
334 unsigned int reset_counter = i915_reset_counter(&dev_priv->gpu_error);
335 struct drm_i915_gem_request *req;
339 /* ABI: Before userspace accesses the GPU (e.g. execbuffer), report
340 * EIO if the GPU is already wedged, or EAGAIN to drop the struct_mutex
343 ret = i915_gem_check_wedge(reset_counter, dev_priv->mm.interruptible);
347 /* Move the oldest request to the slab-cache (if not in use!) */
348 req = list_first_entry_or_null(&engine->request_list,
350 if (req && i915_gem_request_completed(req))
351 i915_gem_request_retire(req);
353 /* Beware: Dragons be flying overhead.
355 * We use RCU to look up requests in flight. The lookups may
356 * race with the request being allocated from the slab freelist.
357 * That is the request we are writing to here, may be in the process
358 * of being read by __i915_gem_active_get_rcu(). As such,
359 * we have to be very careful when overwriting the contents. During
360 * the RCU lookup, we change chase the request->engine pointer,
361 * read the request->fence.seqno and increment the reference count.
363 * The reference count is incremented atomically. If it is zero,
364 * the lookup knows the request is unallocated and complete. Otherwise,
365 * it is either still in use, or has been reallocated and reset
366 * with fence_init(). This increment is safe for release as we check
367 * that the request we have a reference to and matches the active
370 * Before we increment the refcount, we chase the request->engine
371 * pointer. We must not call kmem_cache_zalloc() or else we set
372 * that pointer to NULL and cause a crash during the lookup. If
373 * we see the request is completed (based on the value of the
374 * old engine and seqno), the lookup is complete and reports NULL.
375 * If we decide the request is not completed (new engine or seqno),
376 * then we grab a reference and double check that it is still the
377 * active request - which it won't be and restart the lookup.
379 * Do not use kmem_cache_zalloc() here!
381 req = kmem_cache_alloc(dev_priv->requests, GFP_KERNEL);
383 return ERR_PTR(-ENOMEM);
385 ret = i915_gem_get_seqno(dev_priv, &seqno);
389 spin_lock_init(&req->lock);
390 fence_init(&req->fence,
393 engine->fence_context,
396 INIT_LIST_HEAD(&req->active_list);
397 req->i915 = dev_priv;
398 req->engine = engine;
399 req->ctx = i915_gem_context_get(ctx);
401 /* No zalloc, must clear what we need by hand */
402 req->previous_context = NULL;
403 req->file_priv = NULL;
405 req->elsp_submitted = 0;
408 * Reserve space in the ring buffer for all the commands required to
409 * eventually emit this request. This is to guarantee that the
410 * i915_add_request() call can't fail. Note that the reserve may need
411 * to be redone if the request is not actually submitted straight
412 * away, e.g. because a GPU scheduler has deferred it.
414 req->reserved_space = MIN_SPACE_FOR_ADD_REQUEST;
416 if (i915.enable_execlists)
417 ret = intel_logical_ring_alloc_request_extras(req);
419 ret = intel_ring_alloc_request_extras(req);
423 /* Record the position of the start of the request so that
424 * should we detect the updated seqno part-way through the
425 * GPU processing the request, we never over-estimate the
426 * position of the head.
428 req->head = req->ring->tail;
433 i915_gem_context_put(ctx);
435 kmem_cache_free(dev_priv->requests, req);
439 static void i915_gem_mark_busy(const struct intel_engine_cs *engine)
441 struct drm_i915_private *dev_priv = engine->i915;
443 dev_priv->gt.active_engines |= intel_engine_flag(engine);
444 if (dev_priv->gt.awake)
447 intel_runtime_pm_get_noresume(dev_priv);
448 dev_priv->gt.awake = true;
450 intel_enable_gt_powersave(dev_priv);
451 i915_update_gfx_val(dev_priv);
452 if (INTEL_GEN(dev_priv) >= 6)
453 gen6_rps_busy(dev_priv);
455 queue_delayed_work(dev_priv->wq,
456 &dev_priv->gt.retire_work,
457 round_jiffies_up_relative(HZ));
461 * NB: This function is not allowed to fail. Doing so would mean the the
462 * request is not being tracked for completion but the work itself is
463 * going to happen on the hardware. This would be a Bad Thing(tm).
465 void __i915_add_request(struct drm_i915_gem_request *request, bool flush_caches)
467 struct intel_engine_cs *engine = request->engine;
468 struct intel_ring *ring = request->ring;
474 * To ensure that this call will not fail, space for its emissions
475 * should already have been reserved in the ring buffer. Let the ring
476 * know that it is time to use that space up.
478 request_start = ring->tail;
479 reserved_tail = request->reserved_space;
480 request->reserved_space = 0;
483 * Emit any outstanding flushes - execbuf can fail to emit the flush
484 * after having emitted the batchbuffer command. Hence we need to fix
485 * things up similar to emitting the lazy request. The difference here
486 * is that the flush _must_ happen before the next request, no matter
490 ret = engine->emit_flush(request, EMIT_FLUSH);
492 /* Not allowed to fail! */
493 WARN(ret, "engine->emit_flush() failed: %d!\n", ret);
496 trace_i915_gem_request_add(request);
498 /* Seal the request and mark it as pending execution. Note that
499 * we may inspect this state, without holding any locks, during
500 * hangcheck. Hence we apply the barrier to ensure that we do not
501 * see a more recent value in the hws than we are tracking.
503 request->emitted_jiffies = jiffies;
504 request->previous_seqno = engine->last_submitted_seqno;
505 engine->last_submitted_seqno = request->fence.seqno;
506 i915_gem_active_set(&engine->last_request, request);
507 list_add_tail(&request->link, &engine->request_list);
508 list_add_tail(&request->ring_link, &ring->request_list);
510 /* Record the position of the start of the breadcrumb so that
511 * should we detect the updated seqno part-way through the
512 * GPU processing the request, we never over-estimate the
513 * position of the ring's HEAD.
515 request->postfix = ring->tail;
517 /* Not allowed to fail! */
518 ret = engine->emit_request(request);
519 WARN(ret, "(%s)->emit_request failed: %d!\n", engine->name, ret);
521 /* Sanity check that the reserved size was large enough. */
522 ret = ring->tail - request_start;
525 WARN_ONCE(ret > reserved_tail,
526 "Not enough space reserved (%d bytes) "
527 "for adding the request (%d bytes)\n",
530 i915_gem_mark_busy(engine);
531 engine->submit_request(request);
534 static unsigned long local_clock_us(unsigned int *cpu)
538 /* Cheaply and approximately convert from nanoseconds to microseconds.
539 * The result and subsequent calculations are also defined in the same
540 * approximate microseconds units. The principal source of timing
541 * error here is from the simple truncation.
543 * Note that local_clock() is only defined wrt to the current CPU;
544 * the comparisons are no longer valid if we switch CPUs. Instead of
545 * blocking preemption for the entire busywait, we can detect the CPU
546 * switch and use that as indicator of system load and a reason to
547 * stop busywaiting, see busywait_stop().
550 t = local_clock() >> 10;
556 static bool busywait_stop(unsigned long timeout, unsigned int cpu)
558 unsigned int this_cpu;
560 if (time_after(local_clock_us(&this_cpu), timeout))
563 return this_cpu != cpu;
566 bool __i915_spin_request(const struct drm_i915_gem_request *req,
567 int state, unsigned long timeout_us)
571 /* When waiting for high frequency requests, e.g. during synchronous
572 * rendering split between the CPU and GPU, the finite amount of time
573 * required to set up the irq and wait upon it limits the response
574 * rate. By busywaiting on the request completion for a short while we
575 * can service the high frequency waits as quick as possible. However,
576 * if it is a slow request, we want to sleep as quickly as possible.
577 * The tradeoff between waiting and sleeping is roughly the time it
578 * takes to sleep on a request, on the order of a microsecond.
581 timeout_us += local_clock_us(&cpu);
583 if (i915_gem_request_completed(req))
586 if (signal_pending_state(state, current))
589 if (busywait_stop(timeout_us, cpu))
592 cpu_relax_lowlatency();
593 } while (!need_resched());
599 * i915_wait_request - wait until execution of request has finished
601 * @interruptible: do an interruptible wait (normally yes)
602 * @timeout: in - how long to wait (NULL forever); out - how much time remaining
603 * @rps: client to charge for RPS boosting
605 * Note: It is of utmost importance that the passed in seqno and reset_counter
606 * values have been read by the caller in an smp safe manner. Where read-side
607 * locks are involved, it is sufficient to read the reset_counter before
608 * unlocking the lock that protects the seqno. For lockless tricks, the
609 * reset_counter _must_ be read before, and an appropriate smp_rmb must be
612 * Returns 0 if the request was found within the alloted time. Else returns the
613 * errno with remaining time filled in timeout argument.
615 int i915_wait_request(struct drm_i915_gem_request *req,
618 struct intel_rps_client *rps)
620 int state = interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
622 struct intel_wait wait;
623 unsigned long timeout_remain;
628 if (i915_gem_request_completed(req))
631 timeout_remain = MAX_SCHEDULE_TIMEOUT;
633 if (WARN_ON(*timeout < 0))
639 /* Record current time in case interrupted, or wedged */
640 timeout_remain = nsecs_to_jiffies_timeout(*timeout);
641 *timeout += ktime_get_raw_ns();
644 trace_i915_gem_request_wait_begin(req);
646 /* This client is about to stall waiting for the GPU. In many cases
647 * this is undesirable and limits the throughput of the system, as
648 * many clients cannot continue processing user input/output whilst
649 * blocked. RPS autotuning may take tens of milliseconds to respond
650 * to the GPU load and thus incurs additional latency for the client.
651 * We can circumvent that by promoting the GPU frequency to maximum
652 * before we wait. This makes the GPU throttle up much more quickly
653 * (good for benchmarks and user experience, e.g. window animations),
654 * but at a cost of spending more power processing the workload
655 * (bad for battery). Not all clients even want their results
656 * immediately and for them we should just let the GPU select its own
657 * frequency to maximise efficiency. To prevent a single client from
658 * forcing the clocks too high for the whole system, we only allow
659 * each client to waitboost once in a busy period.
661 if (IS_RPS_CLIENT(rps) && INTEL_GEN(req->i915) >= 6)
662 gen6_rps_boost(req->i915, rps, req->emitted_jiffies);
664 /* Optimistic short spin before touching IRQs */
665 if (i915_spin_request(req, state, 5))
668 set_current_state(state);
669 add_wait_queue(&req->i915->gpu_error.wait_queue, &reset);
671 intel_wait_init(&wait, req->fence.seqno);
672 if (intel_engine_add_wait(req->engine, &wait))
673 /* In order to check that we haven't missed the interrupt
674 * as we enabled it, we need to kick ourselves to do a
675 * coherent check on the seqno before we sleep.
680 if (signal_pending_state(state, current)) {
685 timeout_remain = io_schedule_timeout(timeout_remain);
686 if (timeout_remain == 0) {
691 if (intel_wait_complete(&wait))
694 set_current_state(state);
697 /* Carefully check if the request is complete, giving time
698 * for the seqno to be visible following the interrupt.
699 * We also have to check in case we are kicked by the GPU
700 * reset in order to drop the struct_mutex.
702 if (__i915_request_irq_complete(req))
705 /* Only spin if we know the GPU is processing this request */
706 if (i915_spin_request(req, state, 2))
709 remove_wait_queue(&req->i915->gpu_error.wait_queue, &reset);
711 intel_engine_remove_wait(req->engine, &wait);
712 __set_current_state(TASK_RUNNING);
714 trace_i915_gem_request_wait_end(req);
717 *timeout -= ktime_get_raw_ns();
722 * Apparently ktime isn't accurate enough and occasionally has a
723 * bit of mismatch in the jiffies<->nsecs<->ktime loop. So patch
724 * things up to make the test happy. We allow up to 1 jiffy.
726 * This is a regrssion from the timespec->ktime conversion.
728 if (ret == -ETIME && *timeout < jiffies_to_usecs(1)*1000)
732 if (IS_RPS_USER(rps) &&
733 req->fence.seqno == req->engine->last_submitted_seqno) {
734 /* The GPU is now idle and this client has stalled.
735 * Since no other client has submitted a request in the
736 * meantime, assume that this client is the only one
737 * supplying work to the GPU but is unable to keep that
738 * work supplied because it is waiting. Since the GPU is
739 * then never kept fully busy, RPS autoclocking will
740 * keep the clocks relatively low, causing further delays.
741 * Compensate by giving the synchronous client credit for
742 * a waitboost next time.
744 spin_lock(&req->i915->rps.client_lock);
745 list_del_init(&rps->link);
746 spin_unlock(&req->i915->rps.client_lock);
752 static void engine_retire_requests(struct intel_engine_cs *engine)
754 struct drm_i915_gem_request *request, *next;
756 list_for_each_entry_safe(request, next, &engine->request_list, link) {
757 if (!i915_gem_request_completed(request))
760 i915_gem_request_retire(request);
764 void i915_gem_retire_requests(struct drm_i915_private *dev_priv)
766 struct intel_engine_cs *engine;
768 lockdep_assert_held(&dev_priv->drm.struct_mutex);
770 if (dev_priv->gt.active_engines == 0)
773 GEM_BUG_ON(!dev_priv->gt.awake);
775 for_each_engine(engine, dev_priv) {
776 engine_retire_requests(engine);
777 if (!intel_engine_is_active(engine))
778 dev_priv->gt.active_engines &= ~intel_engine_flag(engine);
781 if (dev_priv->gt.active_engines == 0)
782 queue_delayed_work(dev_priv->wq,
783 &dev_priv->gt.idle_work,
784 msecs_to_jiffies(100));