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 */
35struct 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