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/* SPDX-License-Identifier: MIT */
/*
* Copyright © 2019 Intel Corporation
*/
#ifndef __INTEL_BREADCRUMBS_TYPES__
#define __INTEL_BREADCRUMBS_TYPES__
#include <linux/irq_work.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/types.h>
/*
* 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 {
atomic_t active;
spinlock_t signalers_lock; /* protects the list of signalers */
struct list_head signalers;
struct llist_head signaled_requests;
atomic_t signaler_active;
spinlock_t irq_lock; /* protects the interrupt from hardirq context */
struct irq_work irq_work; /* for use from inside irq_lock */
unsigned int irq_enabled;
bool irq_armed;
/* Not all breadcrumbs are attached to physical HW */
struct intel_engine_cs *irq_engine;
};
#endif /* __INTEL_BREADCRUMBS_TYPES__ */
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