drivers/gpu/drm/i915/gt/intel_engine_pm.c

   1 // SPDX-License-Identifier: MIT
   2 /*
   3  * Copyright © 2019 Intel Corporation
   4  */
   5
   6 #include "i915_drv.h"
   7
   8 #include "intel_breadcrumbs.h"
   9 #include "intel_context.h"
  10 #include "intel_engine.h"
  11 #include "intel_engine_heartbeat.h"
  12 #include "intel_engine_pm.h"
  13 #include "intel_gt.h"
  14 #include "intel_gt_pm.h"
  15 #include "intel_rc6.h"
  16 #include "intel_ring.h"
  17 #include "shmem_utils.h"
  18
  19 static void dbg_poison_ce(struct intel_context *ce)
  20 {
  21         if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
  22                 return;
  23
  24         if (ce->state) {
  25                 struct drm_i915_gem_object *obj = ce->state->obj;
  26                 int type = i915_coherent_map_type(ce->engine->i915, obj, true);
  27                 void *map;
  28
  29                 if (!i915_gem_object_trylock(obj, NULL))
  30                         return;
  31
  32                 map = i915_gem_object_pin_map(obj, type);
  33                 if (!IS_ERR(map)) {
  34                         memset(map, CONTEXT_REDZONE, obj->base.size);
  35                         i915_gem_object_flush_map(obj);
  36                         i915_gem_object_unpin_map(obj);
  37                 }
  38                 i915_gem_object_unlock(obj);
  39         }
  40 }
  41
  42 static int __engine_unpark(struct intel_wakeref *wf)
  43 {
  44         struct intel_engine_cs *engine =
  45                 container_of(wf, typeof(*engine), wakeref);
  46         struct intel_context *ce;
  47
  48         ENGINE_TRACE(engine, "\n");
  49
  50         intel_gt_pm_get(engine->gt);
  51
  52         /* Discard stale context state from across idling */
  53         ce = engine->kernel_context;
  54         if (ce) {
  55                 GEM_BUG_ON(test_bit(CONTEXT_VALID_BIT, &ce->flags));
  56
  57                 /* Flush all pending HW writes before we touch the context */
  58                 while (unlikely(intel_context_inflight(ce)))
  59                         intel_engine_flush_submission(engine);
  60
  61                 /* First poison the image to verify we never fully trust it */
  62                 dbg_poison_ce(ce);
  63
  64                 /* Scrub the context image after our loss of control */
  65                 ce->ops->reset(ce);
  66
  67                 CE_TRACE(ce, "reset { seqno:%x, *hwsp:%x, ring:%x }\n",
  68                          ce->timeline->seqno,
  69                          READ_ONCE(*ce->timeline->hwsp_seqno),
  70                          ce->ring->emit);
  71                 GEM_BUG_ON(ce->timeline->seqno !=
  72                            READ_ONCE(*ce->timeline->hwsp_seqno));
  73         }
  74
  75         if (engine->unpark)
  76                 engine->unpark(engine);
  77
  78         intel_breadcrumbs_unpark(engine->breadcrumbs);
  79         intel_engine_unpark_heartbeat(engine);
  80         return 0;
  81 }
  82
  83 static void duration(struct dma_fence *fence, struct dma_fence_cb *cb)
  84 {
  85         struct i915_request *rq = to_request(fence);
  86
  87         ewma__engine_latency_add(&rq->engine->latency,
  88                                  ktime_us_delta(rq->fence.timestamp,
  89                                                 rq->duration.emitted));
  90 }
  91
  92 static void
  93 __queue_and_release_pm(struct i915_request *rq,
  94                        struct intel_timeline *tl,
  95                        struct intel_engine_cs *engine)
  96 {
  97         struct intel_gt_timelines *timelines = &engine->gt->timelines;
  98
  99         ENGINE_TRACE(engine, "parking\n");
 100
 101         /*
 102          * We have to serialise all potential retirement paths with our
 103          * submission, as we don't want to underflow either the
 104          * engine->wakeref.counter or our timeline->active_count.
 105          *
 106          * Equally, we cannot allow a new submission to start until
 107          * after we finish queueing, nor could we allow that submitter
 108          * to retire us before we are ready!
 109          */
 110         spin_lock(&timelines->lock);
 111
 112         /* Let intel_gt_retire_requests() retire us (acquired under lock) */
 113         if (!atomic_fetch_inc(&tl->active_count))
 114                 list_add_tail(&tl->link, &timelines->active_list);
 115
 116         /* Hand the request over to HW and so engine_retire() */
 117         __i915_request_queue_bh(rq);
 118
 119         /* Let new submissions commence (and maybe retire this timeline) */
 120         __intel_wakeref_defer_park(&engine->wakeref);
 121
 122         spin_unlock(&timelines->lock);
 123 }
 124
 125 static bool switch_to_kernel_context(struct intel_engine_cs *engine)
 126 {
 127         struct intel_context *ce = engine->kernel_context;
 128         struct i915_request *rq;
 129         bool result = true;
 130
 131         /*
 132          * This is execlist specific behaviour intended to ensure the GPU is
 133          * idle by switching to a known 'safe' context. With GuC submission, the
 134          * same idle guarantee is achieved by other means (disabling
 135          * scheduling). Further, switching to a 'safe' context has no effect
 136          * with GuC submission as the scheduler can just switch back again.
 137          *
 138          * FIXME: Move this backend scheduler specific behaviour into the
 139          * scheduler backend.
 140          */
 141         if (intel_engine_uses_guc(engine))
 142                 return true;
 143
 144         /* GPU is pointing to the void, as good as in the kernel context. */
 145         if (intel_gt_is_wedged(engine->gt))
 146                 return true;
 147
 148         GEM_BUG_ON(!intel_context_is_barrier(ce));
 149         GEM_BUG_ON(ce->timeline->hwsp_ggtt != engine->status_page.vma);
 150
 151         /* Already inside the kernel context, safe to power down. */
 152         if (engine->wakeref_serial == engine->serial)
 153                 return true;
 154
 155         /*
 156          * Note, we do this without taking the timeline->mutex. We cannot
 157          * as we may be called while retiring the kernel context and so
 158          * already underneath the timeline->mutex. Instead we rely on the
 159          * exclusive property of the __engine_park that prevents anyone
 160          * else from creating a request on this engine. This also requires
 161          * that the ring is empty and we avoid any waits while constructing
 162          * the context, as they assume protection by the timeline->mutex.
 163          * This should hold true as we can only park the engine after
 164          * retiring the last request, thus all rings should be empty and
 165          * all timelines idle.
 166          *
 167          * For unlocking, there are 2 other parties and the GPU who have a
 168          * stake here.
 169          *
 170          * A new gpu user will be waiting on the engine-pm to start their
 171          * engine_unpark. New waiters are predicated on engine->wakeref.count
 172          * and so intel_wakeref_defer_park() acts like a mutex_unlock of the
 173          * engine->wakeref.
 174          *
 175          * The other party is intel_gt_retire_requests(), which is walking the
 176          * list of active timelines looking for completions. Meanwhile as soon
 177          * as we call __i915_request_queue(), the GPU may complete our request.
 178          * Ergo, if we put ourselves on the timelines.active_list
 179          * (se intel_timeline_enter()) before we increment the
 180          * engine->wakeref.count, we may see the request completion and retire
 181          * it causing an underflow of the engine->wakeref.
 182          */
 183         set_bit(CONTEXT_IS_PARKING, &ce->flags);
 184         GEM_BUG_ON(atomic_read(&ce->timeline->active_count) < 0);
 185
 186         rq = __i915_request_create(ce, GFP_NOWAIT);
 187         if (IS_ERR(rq))
 188                 /* Context switch failed, hope for the best! Maybe reset? */
 189                 goto out_unlock;
 190
 191         /* Check again on the next retirement. */
 192         engine->wakeref_serial = engine->serial + 1;
 193         i915_request_add_active_barriers(rq);
 194
 195         /* Install ourselves as a preemption barrier */
 196         rq->sched.attr.priority = I915_PRIORITY_BARRIER;
 197         if (likely(!__i915_request_commit(rq))) { /* engine should be idle! */
 198                 /*
 199                  * Use an interrupt for precise measurement of duration,
 200                  * otherwise we rely on someone else retiring all the requests
 201                  * which may delay the signaling (i.e. we will likely wait
 202                  * until the background request retirement running every
 203                  * second or two).
 204                  */
 205                 BUILD_BUG_ON(sizeof(rq->duration) > sizeof(rq->submitq));
 206                 dma_fence_add_callback(&rq->fence, &rq->duration.cb, duration);
 207                 rq->duration.emitted = ktime_get();
 208         }
 209
 210         /* Expose ourselves to the world */
 211         __queue_and_release_pm(rq, ce->timeline, engine);
 212
 213         result = false;
 214 out_unlock:
 215         clear_bit(CONTEXT_IS_PARKING, &ce->flags);
 216         return result;
 217 }
 218
 219 static void call_idle_barriers(struct intel_engine_cs *engine)
 220 {
 221         struct llist_node *node, *next;
 222
 223         llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks)) {
 224                 struct dma_fence_cb *cb =
 225                         container_of((struct list_head *)node,
 226                                      typeof(*cb), node);
 227
 228                 cb->func(ERR_PTR(-EAGAIN), cb);
 229         }
 230 }
 231
 232 static int __engine_park(struct intel_wakeref *wf)
 233 {
 234         struct intel_engine_cs *engine =
 235                 container_of(wf, typeof(*engine), wakeref);
 236
 237         engine->saturated = 0;
 238
 239         /*
 240          * If one and only one request is completed between pm events,
 241          * we know that we are inside the kernel context and it is
 242          * safe to power down. (We are paranoid in case that runtime
 243          * suspend causes corruption to the active context image, and
 244          * want to avoid that impacting userspace.)
 245          */
 246         if (!switch_to_kernel_context(engine))
 247                 return -EBUSY;
 248
 249         ENGINE_TRACE(engine, "parked\n");
 250
 251         call_idle_barriers(engine); /* cleanup after wedging */
 252
 253         intel_engine_park_heartbeat(engine);
 254         intel_breadcrumbs_park(engine->breadcrumbs);
 255
 256         /* Must be reset upon idling, or we may miss the busy wakeup. */
 257         GEM_BUG_ON(engine->sched_engine->queue_priority_hint != INT_MIN);
 258
 259         if (engine->park)
 260                 engine->park(engine);
 261
 262         /* While gt calls i915_vma_parked(), we have to break the lock cycle */
 263         intel_gt_pm_put_async(engine->gt);
 264         return 0;
 265 }
 266
 267 static const struct intel_wakeref_ops wf_ops = {
 268         .get = __engine_unpark,
 269         .put = __engine_park,
 270 };
 271
 272 void intel_engine_init__pm(struct intel_engine_cs *engine)
 273 {
 274         struct intel_runtime_pm *rpm = engine->uncore->rpm;
 275
 276         intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
 277         intel_engine_init_heartbeat(engine);
 278 }
 279
 280 /**
 281  * intel_engine_reset_pinned_contexts - Reset the pinned contexts of
 282  * an engine.
 283  * @engine: The engine whose pinned contexts we want to reset.
 284  *
 285  * Typically the pinned context LMEM images lose or get their content
 286  * corrupted on suspend. This function resets their images.
 287  */
 288 void intel_engine_reset_pinned_contexts(struct intel_engine_cs *engine)
 289 {
 290         struct intel_context *ce;
 291
 292         list_for_each_entry(ce, &engine->pinned_contexts_list,
 293                             pinned_contexts_link) {
 294                 /* kernel context gets reset at __engine_unpark() */
 295                 if (ce == engine->kernel_context)
 296                         continue;
 297
 298                 dbg_poison_ce(ce);
 299                 ce->ops->reset(ce);
 300         }
 301 }
 302
 303 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 304 #include "selftest_engine_pm.c"
 305 #endif