1 /* SPDX-License-Identifier: MIT */ 2 /* 3 * Copyright © 2019 Intel Corporation 4 */ 5 6 #ifndef __INTEL_BREADCRUMBS_TYPES__ 7 #define __INTEL_BREADCRUMBS_TYPES__ 8 9 #include <linux/irq_work.h> 10 #include <linux/kref.h> 11 #include <linux/list.h> 12 #include <linux/spinlock.h> 13 #include <linux/types.h> 14 15 #include "intel_engine_types.h" 16 #include "intel_wakeref.h" 17 18 /* 19 * Rather than have every client wait upon all user interrupts, 20 * with the herd waking after every interrupt and each doing the 21 * heavyweight seqno dance, we delegate the task (of being the 22 * bottom-half of the user interrupt) to the first client. After 23 * every interrupt, we wake up one client, who does the heavyweight 24 * coherent seqno read and either goes back to sleep (if incomplete), 25 * or wakes up all the completed clients in parallel, before then 26 * transferring the bottom-half status to the next client in the queue. 27 * 28 * Compared to walking the entire list of waiters in a single dedicated 29 * bottom-half, we reduce the latency of the first waiter by avoiding 30 * a context switch, but incur additional coherent seqno reads when 31 * following the chain of request breadcrumbs. Since it is most likely 32 * that we have a single client waiting on each seqno, then reducing 33 * the overhead of waking that client is much preferred. 34 */ 35 struct intel_breadcrumbs { 36 struct kref ref; 37 atomic_t active; 38 39 spinlock_t signalers_lock; /* protects the list of signalers */ 40 struct list_head signalers; 41 struct llist_head signaled_requests; 42 atomic_t signaler_active; 43 44 spinlock_t irq_lock; /* protects the interrupt from hardirq context */ 45 struct irq_work irq_work; /* for use from inside irq_lock */ 46 unsigned int irq_enabled; 47 intel_wakeref_t irq_armed; 48 49 /* Not all breadcrumbs are attached to physical HW */ 50 intel_engine_mask_t engine_mask; 51 struct intel_engine_cs *irq_engine; 52 bool (*irq_enable)(struct intel_breadcrumbs *b); 53 void (*irq_disable)(struct intel_breadcrumbs *b); 54 }; 55 56 #endif /* __INTEL_BREADCRUMBS_TYPES__ */ 57