diff options
Diffstat (limited to 'drivers/gpu/drm/i915/intel_ringbuffer.h')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_ringbuffer.h | 79 |
1 files changed, 77 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 113d5230a6de..6fd70a56e219 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -148,6 +148,32 @@ struct intel_engine_cs { struct intel_ringbuffer *buffer; struct list_head buffers; + /* Rather than have every client wait upon all user interrupts, + * with the herd waking after every interrupt and each doing the + * heavyweight seqno dance, we delegate the task (of being the + * bottom-half of the user interrupt) to the first client. After + * every interrupt, we wake up one client, who does the heavyweight + * coherent seqno read and either goes back to sleep (if incomplete), + * or wakes up all the completed clients in parallel, before then + * transferring the bottom-half status to the next client in the queue. + * + * Compared to walking the entire list of waiters in a single dedicated + * bottom-half, we reduce the latency of the first waiter by avoiding + * a context switch, but incur additional coherent seqno reads when + * following the chain of request breadcrumbs. Since it is most likely + * that we have a single client waiting on each seqno, then reducing + * the overhead of waking that client is much preferred. + */ + struct intel_breadcrumbs { + spinlock_t lock; /* protects the lists of requests */ + struct rb_root waiters; /* sorted by retirement, priority */ + struct intel_wait *first_wait; /* oldest waiter by retirement */ + struct task_struct *tasklet; /* bh for user interrupts */ + struct timer_list fake_irq; /* used after a missed interrupt */ + bool irq_enabled; + bool rpm_wakelock; + } breadcrumbs; + /* * A pool of objects to use as shadow copies of client batch buffers * when the command parser is enabled. Prevents the client from @@ -296,8 +322,6 @@ struct intel_engine_cs { bool gpu_caches_dirty; - wait_queue_head_t irq_queue; - struct i915_gem_context *last_context; struct intel_ring_hangcheck hangcheck; @@ -483,4 +507,55 @@ static inline u32 intel_hws_seqno_address(struct intel_engine_cs *engine) return engine->status_page.gfx_addr + I915_GEM_HWS_INDEX_ADDR; } +/* intel_breadcrumbs.c -- user interrupt bottom-half for waiters */ +struct intel_wait { + struct rb_node node; + struct task_struct *tsk; + u32 seqno; +}; + +int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine); + +static inline void intel_wait_init(struct intel_wait *wait, u32 seqno) +{ + wait->tsk = current; + wait->seqno = seqno; +} + +static inline bool intel_wait_complete(const struct intel_wait *wait) +{ + return RB_EMPTY_NODE(&wait->node); +} + +bool intel_engine_add_wait(struct intel_engine_cs *engine, + struct intel_wait *wait); +void intel_engine_remove_wait(struct intel_engine_cs *engine, + struct intel_wait *wait); + +static inline bool intel_engine_has_waiter(struct intel_engine_cs *engine) +{ + return READ_ONCE(engine->breadcrumbs.tasklet); +} + +static inline bool intel_engine_wakeup(struct intel_engine_cs *engine) +{ + bool wakeup = false; + struct task_struct *tsk = READ_ONCE(engine->breadcrumbs.tasklet); + /* Note that for this not to dangerously chase a dangling pointer, + * the caller is responsible for ensure that the task remain valid for + * wake_up_process() i.e. that the RCU grace period cannot expire. + * + * Also note that tsk is likely to be in !TASK_RUNNING state so an + * early test for tsk->state != TASK_RUNNING before wake_up_process() + * is unlikely to be beneficial. + */ + if (tsk) + wakeup = wake_up_process(tsk); + return wakeup; +} + +void intel_engine_enable_fake_irq(struct intel_engine_cs *engine); +void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine); +unsigned int intel_kick_waiters(struct drm_i915_private *i915); + #endif /* _INTEL_RINGBUFFER_H_ */ |