/* SPDX-License-Identifier: MIT */
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/*
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* Copyright © 2019 Intel Corporation
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*/
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#ifndef __INTEL_BREADCRUMBS_TYPES__
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#define __INTEL_BREADCRUMBS_TYPES__
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#include <linux/irq_work.h>
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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/*
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* Rather than have every client wait upon all user interrupts,
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* with the herd waking after every interrupt and each doing the
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* heavyweight seqno dance, we delegate the task (of being the
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* bottom-half of the user interrupt) to the first client. After
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* every interrupt, we wake up one client, who does the heavyweight
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* coherent seqno read and either goes back to sleep (if incomplete),
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* or wakes up all the completed clients in parallel, before then
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* transferring the bottom-half status to the next client in the queue.
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*
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* Compared to walking the entire list of waiters in a single dedicated
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* bottom-half, we reduce the latency of the first waiter by avoiding
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* a context switch, but incur additional coherent seqno reads when
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* following the chain of request breadcrumbs. Since it is most likely
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* that we have a single client waiting on each seqno, then reducing
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* the overhead of waking that client is much preferred.
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*/
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struct intel_breadcrumbs {
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/* Not all breadcrumbs are attached to physical HW */
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struct intel_engine_cs *irq_engine;
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spinlock_t signalers_lock; /* protects the list of signalers */
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struct list_head signalers;
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struct llist_head signaled_requests;
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spinlock_t irq_lock; /* protects the interrupt from hardirq context */
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struct irq_work irq_work; /* for use from inside irq_lock */
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unsigned int irq_enabled;
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bool irq_armed;
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};
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#endif /* __INTEL_BREADCRUMBS_TYPES__ */
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