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caf4a36e81
Some comments in cpuidle core files contain trivial mistakes. This patch fixes them. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
795 lines
26 KiB
C
795 lines
26 KiB
C
/*
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* coupled.c - helper functions to enter the same idle state on multiple cpus
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*
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* Copyright (c) 2011 Google, Inc.
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*
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* Author: Colin Cross <ccross@android.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <linux/kernel.h>
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#include <linux/cpu.h>
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#include <linux/cpuidle.h>
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#include <linux/mutex.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include "cpuidle.h"
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/**
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* DOC: Coupled cpuidle states
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*
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* On some ARM SMP SoCs (OMAP4460, Tegra 2, and probably more), the
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* cpus cannot be independently powered down, either due to
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* sequencing restrictions (on Tegra 2, cpu 0 must be the last to
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* power down), or due to HW bugs (on OMAP4460, a cpu powering up
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* will corrupt the gic state unless the other cpu runs a work
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* around). Each cpu has a power state that it can enter without
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* coordinating with the other cpu (usually Wait For Interrupt, or
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* WFI), and one or more "coupled" power states that affect blocks
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* shared between the cpus (L2 cache, interrupt controller, and
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* sometimes the whole SoC). Entering a coupled power state must
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* be tightly controlled on both cpus.
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*
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* This file implements a solution, where each cpu will wait in the
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* WFI state until all cpus are ready to enter a coupled state, at
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* which point the coupled state function will be called on all
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* cpus at approximately the same time.
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*
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* Once all cpus are ready to enter idle, they are woken by an smp
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* cross call. At this point, there is a chance that one of the
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* cpus will find work to do, and choose not to enter idle. A
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* final pass is needed to guarantee that all cpus will call the
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* power state enter function at the same time. During this pass,
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* each cpu will increment the ready counter, and continue once the
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* ready counter matches the number of online coupled cpus. If any
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* cpu exits idle, the other cpus will decrement their counter and
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* retry.
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*
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* requested_state stores the deepest coupled idle state each cpu
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* is ready for. It is assumed that the states are indexed from
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* shallowest (highest power, lowest exit latency) to deepest
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* (lowest power, highest exit latency). The requested_state
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* variable is not locked. It is only written from the cpu that
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* it stores (or by the on/offlining cpu if that cpu is offline),
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* and only read after all the cpus are ready for the coupled idle
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* state are are no longer updating it.
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*
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* Three atomic counters are used. alive_count tracks the number
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* of cpus in the coupled set that are currently or soon will be
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* online. waiting_count tracks the number of cpus that are in
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* the waiting loop, in the ready loop, or in the coupled idle state.
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* ready_count tracks the number of cpus that are in the ready loop
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* or in the coupled idle state.
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*
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* To use coupled cpuidle states, a cpuidle driver must:
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*
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* Set struct cpuidle_device.coupled_cpus to the mask of all
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* coupled cpus, usually the same as cpu_possible_mask if all cpus
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* are part of the same cluster. The coupled_cpus mask must be
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* set in the struct cpuidle_device for each cpu.
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*
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* Set struct cpuidle_device.safe_state to a state that is not a
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* coupled state. This is usually WFI.
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*
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* Set CPUIDLE_FLAG_COUPLED in struct cpuidle_state.flags for each
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* state that affects multiple cpus.
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*
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* Provide a struct cpuidle_state.enter function for each state
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* that affects multiple cpus. This function is guaranteed to be
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* called on all cpus at approximately the same time. The driver
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* should ensure that the cpus all abort together if any cpu tries
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* to abort once the function is called. The function should return
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* with interrupts still disabled.
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*/
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/**
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* struct cpuidle_coupled - data for set of cpus that share a coupled idle state
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* @coupled_cpus: mask of cpus that are part of the coupled set
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* @requested_state: array of requested states for cpus in the coupled set
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* @ready_waiting_counts: combined count of cpus in ready or waiting loops
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* @online_count: count of cpus that are online
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* @refcnt: reference count of cpuidle devices that are using this struct
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* @prevent: flag to prevent coupled idle while a cpu is hotplugging
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*/
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struct cpuidle_coupled {
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cpumask_t coupled_cpus;
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int requested_state[NR_CPUS];
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atomic_t ready_waiting_counts;
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atomic_t abort_barrier;
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int online_count;
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int refcnt;
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int prevent;
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};
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#define WAITING_BITS 16
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#define MAX_WAITING_CPUS (1 << WAITING_BITS)
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#define WAITING_MASK (MAX_WAITING_CPUS - 1)
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#define READY_MASK (~WAITING_MASK)
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#define CPUIDLE_COUPLED_NOT_IDLE (-1)
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static DEFINE_MUTEX(cpuidle_coupled_lock);
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static DEFINE_PER_CPU(struct call_single_data, cpuidle_coupled_poke_cb);
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/*
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* The cpuidle_coupled_poke_pending mask is used to avoid calling
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* __smp_call_function_single with the per cpu call_single_data struct already
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* in use. This prevents a deadlock where two cpus are waiting for each others
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* call_single_data struct to be available
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*/
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static cpumask_t cpuidle_coupled_poke_pending;
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/*
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* The cpuidle_coupled_poked mask is used to ensure that each cpu has been poked
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* once to minimize entering the ready loop with a poke pending, which would
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* require aborting and retrying.
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*/
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static cpumask_t cpuidle_coupled_poked;
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/**
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* cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus
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* @dev: cpuidle_device of the calling cpu
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* @a: atomic variable to hold the barrier
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*
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* No caller to this function will return from this function until all online
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* cpus in the same coupled group have called this function. Once any caller
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* has returned from this function, the barrier is immediately available for
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* reuse.
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*
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* The atomic variable must be initialized to 0 before any cpu calls
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* this function, will be reset to 0 before any cpu returns from this function.
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*
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* Must only be called from within a coupled idle state handler
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* (state.enter when state.flags has CPUIDLE_FLAG_COUPLED set).
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*
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* Provides full smp barrier semantics before and after calling.
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*/
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void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a)
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{
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int n = dev->coupled->online_count;
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smp_mb__before_atomic_inc();
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atomic_inc(a);
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while (atomic_read(a) < n)
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cpu_relax();
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if (atomic_inc_return(a) == n * 2) {
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atomic_set(a, 0);
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return;
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}
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while (atomic_read(a) > n)
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cpu_relax();
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}
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/**
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* cpuidle_state_is_coupled - check if a state is part of a coupled set
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* @dev: struct cpuidle_device for the current cpu
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* @drv: struct cpuidle_driver for the platform
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* @state: index of the target state in drv->states
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*
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* Returns true if the target state is coupled with cpus besides this one
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*/
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bool cpuidle_state_is_coupled(struct cpuidle_device *dev,
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struct cpuidle_driver *drv, int state)
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{
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return drv->states[state].flags & CPUIDLE_FLAG_COUPLED;
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}
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/**
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* cpuidle_coupled_set_ready - mark a cpu as ready
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* @coupled: the struct coupled that contains the current cpu
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*/
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static inline void cpuidle_coupled_set_ready(struct cpuidle_coupled *coupled)
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{
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atomic_add(MAX_WAITING_CPUS, &coupled->ready_waiting_counts);
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}
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/**
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* cpuidle_coupled_set_not_ready - mark a cpu as not ready
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* @coupled: the struct coupled that contains the current cpu
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*
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* Decrements the ready counter, unless the ready (and thus the waiting) counter
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* is equal to the number of online cpus. Prevents a race where one cpu
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* decrements the waiting counter and then re-increments it just before another
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* cpu has decremented its ready counter, leading to the ready counter going
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* down from the number of online cpus without going through the coupled idle
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* state.
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*
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* Returns 0 if the counter was decremented successfully, -EINVAL if the ready
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* counter was equal to the number of online cpus.
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*/
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static
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inline int cpuidle_coupled_set_not_ready(struct cpuidle_coupled *coupled)
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{
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int all;
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int ret;
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all = coupled->online_count | (coupled->online_count << WAITING_BITS);
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ret = atomic_add_unless(&coupled->ready_waiting_counts,
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-MAX_WAITING_CPUS, all);
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return ret ? 0 : -EINVAL;
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}
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/**
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* cpuidle_coupled_no_cpus_ready - check if no cpus in a coupled set are ready
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* @coupled: the struct coupled that contains the current cpu
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*
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* Returns true if all of the cpus in a coupled set are out of the ready loop.
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*/
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static inline int cpuidle_coupled_no_cpus_ready(struct cpuidle_coupled *coupled)
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{
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int r = atomic_read(&coupled->ready_waiting_counts) >> WAITING_BITS;
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return r == 0;
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}
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/**
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* cpuidle_coupled_cpus_ready - check if all cpus in a coupled set are ready
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* @coupled: the struct coupled that contains the current cpu
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*
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* Returns true if all cpus coupled to this target state are in the ready loop
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*/
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static inline bool cpuidle_coupled_cpus_ready(struct cpuidle_coupled *coupled)
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{
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int r = atomic_read(&coupled->ready_waiting_counts) >> WAITING_BITS;
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return r == coupled->online_count;
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}
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/**
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* cpuidle_coupled_cpus_waiting - check if all cpus in a coupled set are waiting
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* @coupled: the struct coupled that contains the current cpu
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*
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* Returns true if all cpus coupled to this target state are in the wait loop
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*/
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static inline bool cpuidle_coupled_cpus_waiting(struct cpuidle_coupled *coupled)
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{
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int w = atomic_read(&coupled->ready_waiting_counts) & WAITING_MASK;
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return w == coupled->online_count;
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}
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/**
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* cpuidle_coupled_no_cpus_waiting - check if no cpus in coupled set are waiting
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* @coupled: the struct coupled that contains the current cpu
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*
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* Returns true if all of the cpus in a coupled set are out of the waiting loop.
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*/
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static inline int cpuidle_coupled_no_cpus_waiting(struct cpuidle_coupled *coupled)
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{
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int w = atomic_read(&coupled->ready_waiting_counts) & WAITING_MASK;
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return w == 0;
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}
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/**
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* cpuidle_coupled_get_state - determine the deepest idle state
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* @dev: struct cpuidle_device for this cpu
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* @coupled: the struct coupled that contains the current cpu
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*
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* Returns the deepest idle state that all coupled cpus can enter
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*/
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static inline int cpuidle_coupled_get_state(struct cpuidle_device *dev,
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struct cpuidle_coupled *coupled)
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{
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int i;
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int state = INT_MAX;
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/*
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* Read barrier ensures that read of requested_state is ordered after
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* reads of ready_count. Matches the write barriers
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* cpuidle_set_state_waiting.
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*/
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smp_rmb();
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for_each_cpu_mask(i, coupled->coupled_cpus)
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if (cpu_online(i) && coupled->requested_state[i] < state)
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state = coupled->requested_state[i];
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return state;
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}
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static void cpuidle_coupled_handle_poke(void *info)
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{
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int cpu = (unsigned long)info;
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cpumask_set_cpu(cpu, &cpuidle_coupled_poked);
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cpumask_clear_cpu(cpu, &cpuidle_coupled_poke_pending);
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}
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/**
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* cpuidle_coupled_poke - wake up a cpu that may be waiting
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* @cpu: target cpu
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*
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* Ensures that the target cpu exits it's waiting idle state (if it is in it)
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* and will see updates to waiting_count before it re-enters it's waiting idle
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* state.
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*
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* If cpuidle_coupled_poked_mask is already set for the target cpu, that cpu
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* either has or will soon have a pending IPI that will wake it out of idle,
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* or it is currently processing the IPI and is not in idle.
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*/
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static void cpuidle_coupled_poke(int cpu)
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{
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struct call_single_data *csd = &per_cpu(cpuidle_coupled_poke_cb, cpu);
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if (!cpumask_test_and_set_cpu(cpu, &cpuidle_coupled_poke_pending))
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__smp_call_function_single(cpu, csd, 0);
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}
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/**
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* cpuidle_coupled_poke_others - wake up all other cpus that may be waiting
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* @dev: struct cpuidle_device for this cpu
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* @coupled: the struct coupled that contains the current cpu
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*
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* Calls cpuidle_coupled_poke on all other online cpus.
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*/
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static void cpuidle_coupled_poke_others(int this_cpu,
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struct cpuidle_coupled *coupled)
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{
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int cpu;
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for_each_cpu_mask(cpu, coupled->coupled_cpus)
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if (cpu != this_cpu && cpu_online(cpu))
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cpuidle_coupled_poke(cpu);
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}
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/**
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* cpuidle_coupled_set_waiting - mark this cpu as in the wait loop
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* @dev: struct cpuidle_device for this cpu
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* @coupled: the struct coupled that contains the current cpu
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* @next_state: the index in drv->states of the requested state for this cpu
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*
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* Updates the requested idle state for the specified cpuidle device.
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* Returns the number of waiting cpus.
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*/
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static int cpuidle_coupled_set_waiting(int cpu,
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struct cpuidle_coupled *coupled, int next_state)
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{
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coupled->requested_state[cpu] = next_state;
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/*
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* The atomic_inc_return provides a write barrier to order the write
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* to requested_state with the later write that increments ready_count.
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*/
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return atomic_inc_return(&coupled->ready_waiting_counts) & WAITING_MASK;
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}
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/**
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* cpuidle_coupled_set_not_waiting - mark this cpu as leaving the wait loop
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* @dev: struct cpuidle_device for this cpu
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* @coupled: the struct coupled that contains the current cpu
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*
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* Removes the requested idle state for the specified cpuidle device.
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*/
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static void cpuidle_coupled_set_not_waiting(int cpu,
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struct cpuidle_coupled *coupled)
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{
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/*
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* Decrementing waiting count can race with incrementing it in
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* cpuidle_coupled_set_waiting, but that's OK. Worst case, some
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* cpus will increment ready_count and then spin until they
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* notice that this cpu has cleared it's requested_state.
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*/
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atomic_dec(&coupled->ready_waiting_counts);
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coupled->requested_state[cpu] = CPUIDLE_COUPLED_NOT_IDLE;
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}
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/**
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* cpuidle_coupled_set_done - mark this cpu as leaving the ready loop
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* @cpu: the current cpu
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* @coupled: the struct coupled that contains the current cpu
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*
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* Marks this cpu as no longer in the ready and waiting loops. Decrements
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* the waiting count first to prevent another cpu looping back in and seeing
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* this cpu as waiting just before it exits idle.
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*/
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static void cpuidle_coupled_set_done(int cpu, struct cpuidle_coupled *coupled)
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{
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cpuidle_coupled_set_not_waiting(cpu, coupled);
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atomic_sub(MAX_WAITING_CPUS, &coupled->ready_waiting_counts);
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}
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/**
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* cpuidle_coupled_clear_pokes - spin until the poke interrupt is processed
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* @cpu - this cpu
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*
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* Turns on interrupts and spins until any outstanding poke interrupts have
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* been processed and the poke bit has been cleared.
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*
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* Other interrupts may also be processed while interrupts are enabled, so
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* need_resched() must be tested after this function returns to make sure
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* the interrupt didn't schedule work that should take the cpu out of idle.
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*
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* Returns 0 if no poke was pending, 1 if a poke was cleared.
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*/
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static int cpuidle_coupled_clear_pokes(int cpu)
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{
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if (!cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending))
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return 0;
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local_irq_enable();
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while (cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending))
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cpu_relax();
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local_irq_disable();
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return 1;
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}
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static bool cpuidle_coupled_any_pokes_pending(struct cpuidle_coupled *coupled)
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{
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cpumask_t cpus;
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int ret;
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cpumask_and(&cpus, cpu_online_mask, &coupled->coupled_cpus);
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ret = cpumask_and(&cpus, &cpuidle_coupled_poke_pending, &cpus);
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return ret;
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}
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/**
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* cpuidle_enter_state_coupled - attempt to enter a state with coupled cpus
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* @dev: struct cpuidle_device for the current cpu
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* @drv: struct cpuidle_driver for the platform
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* @next_state: index of the requested state in drv->states
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*
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* Coordinate with coupled cpus to enter the target state. This is a two
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* stage process. In the first stage, the cpus are operating independently,
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* and may call into cpuidle_enter_state_coupled at completely different times.
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* To save as much power as possible, the first cpus to call this function will
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* go to an intermediate state (the cpuidle_device's safe state), and wait for
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* all the other cpus to call this function. Once all coupled cpus are idle,
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* the second stage will start. Each coupled cpu will spin until all cpus have
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* guaranteed that they will call the target_state.
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*
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* This function must be called with interrupts disabled. It may enable
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* interrupts while preparing for idle, and it will always return with
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* interrupts enabled.
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*/
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int cpuidle_enter_state_coupled(struct cpuidle_device *dev,
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struct cpuidle_driver *drv, int next_state)
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{
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int entered_state = -1;
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struct cpuidle_coupled *coupled = dev->coupled;
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int w;
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if (!coupled)
|
|
return -EINVAL;
|
|
|
|
while (coupled->prevent) {
|
|
cpuidle_coupled_clear_pokes(dev->cpu);
|
|
if (need_resched()) {
|
|
local_irq_enable();
|
|
return entered_state;
|
|
}
|
|
entered_state = cpuidle_enter_state(dev, drv,
|
|
dev->safe_state_index);
|
|
local_irq_disable();
|
|
}
|
|
|
|
/* Read barrier ensures online_count is read after prevent is cleared */
|
|
smp_rmb();
|
|
|
|
reset:
|
|
cpumask_clear_cpu(dev->cpu, &cpuidle_coupled_poked);
|
|
|
|
w = cpuidle_coupled_set_waiting(dev->cpu, coupled, next_state);
|
|
/*
|
|
* If this is the last cpu to enter the waiting state, poke
|
|
* all the other cpus out of their waiting state so they can
|
|
* enter a deeper state. This can race with one of the cpus
|
|
* exiting the waiting state due to an interrupt and
|
|
* decrementing waiting_count, see comment below.
|
|
*/
|
|
if (w == coupled->online_count) {
|
|
cpumask_set_cpu(dev->cpu, &cpuidle_coupled_poked);
|
|
cpuidle_coupled_poke_others(dev->cpu, coupled);
|
|
}
|
|
|
|
retry:
|
|
/*
|
|
* Wait for all coupled cpus to be idle, using the deepest state
|
|
* allowed for a single cpu. If this was not the poking cpu, wait
|
|
* for at least one poke before leaving to avoid a race where
|
|
* two cpus could arrive at the waiting loop at the same time,
|
|
* but the first of the two to arrive could skip the loop without
|
|
* processing the pokes from the last to arrive.
|
|
*/
|
|
while (!cpuidle_coupled_cpus_waiting(coupled) ||
|
|
!cpumask_test_cpu(dev->cpu, &cpuidle_coupled_poked)) {
|
|
if (cpuidle_coupled_clear_pokes(dev->cpu))
|
|
continue;
|
|
|
|
if (need_resched()) {
|
|
cpuidle_coupled_set_not_waiting(dev->cpu, coupled);
|
|
goto out;
|
|
}
|
|
|
|
if (coupled->prevent) {
|
|
cpuidle_coupled_set_not_waiting(dev->cpu, coupled);
|
|
goto out;
|
|
}
|
|
|
|
entered_state = cpuidle_enter_state(dev, drv,
|
|
dev->safe_state_index);
|
|
local_irq_disable();
|
|
}
|
|
|
|
cpuidle_coupled_clear_pokes(dev->cpu);
|
|
if (need_resched()) {
|
|
cpuidle_coupled_set_not_waiting(dev->cpu, coupled);
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Make sure final poke status for this cpu is visible before setting
|
|
* cpu as ready.
|
|
*/
|
|
smp_wmb();
|
|
|
|
/*
|
|
* All coupled cpus are probably idle. There is a small chance that
|
|
* one of the other cpus just became active. Increment the ready count,
|
|
* and spin until all coupled cpus have incremented the counter. Once a
|
|
* cpu has incremented the ready counter, it cannot abort idle and must
|
|
* spin until either all cpus have incremented the ready counter, or
|
|
* another cpu leaves idle and decrements the waiting counter.
|
|
*/
|
|
|
|
cpuidle_coupled_set_ready(coupled);
|
|
while (!cpuidle_coupled_cpus_ready(coupled)) {
|
|
/* Check if any other cpus bailed out of idle. */
|
|
if (!cpuidle_coupled_cpus_waiting(coupled))
|
|
if (!cpuidle_coupled_set_not_ready(coupled))
|
|
goto retry;
|
|
|
|
cpu_relax();
|
|
}
|
|
|
|
/*
|
|
* Make sure read of all cpus ready is done before reading pending pokes
|
|
*/
|
|
smp_rmb();
|
|
|
|
/*
|
|
* There is a small chance that a cpu left and reentered idle after this
|
|
* cpu saw that all cpus were waiting. The cpu that reentered idle will
|
|
* have sent this cpu a poke, which will still be pending after the
|
|
* ready loop. The pending interrupt may be lost by the interrupt
|
|
* controller when entering the deep idle state. It's not possible to
|
|
* clear a pending interrupt without turning interrupts on and handling
|
|
* it, and it's too late to turn on interrupts here, so reset the
|
|
* coupled idle state of all cpus and retry.
|
|
*/
|
|
if (cpuidle_coupled_any_pokes_pending(coupled)) {
|
|
cpuidle_coupled_set_done(dev->cpu, coupled);
|
|
/* Wait for all cpus to see the pending pokes */
|
|
cpuidle_coupled_parallel_barrier(dev, &coupled->abort_barrier);
|
|
goto reset;
|
|
}
|
|
|
|
/* all cpus have acked the coupled state */
|
|
next_state = cpuidle_coupled_get_state(dev, coupled);
|
|
|
|
entered_state = cpuidle_enter_state(dev, drv, next_state);
|
|
|
|
cpuidle_coupled_set_done(dev->cpu, coupled);
|
|
|
|
out:
|
|
/*
|
|
* Normal cpuidle states are expected to return with irqs enabled.
|
|
* That leads to an inefficiency where a cpu receiving an interrupt
|
|
* that brings it out of idle will process that interrupt before
|
|
* exiting the idle enter function and decrementing ready_count. All
|
|
* other cpus will need to spin waiting for the cpu that is processing
|
|
* the interrupt. If the driver returns with interrupts disabled,
|
|
* all other cpus will loop back into the safe idle state instead of
|
|
* spinning, saving power.
|
|
*
|
|
* Calling local_irq_enable here allows coupled states to return with
|
|
* interrupts disabled, but won't cause problems for drivers that
|
|
* exit with interrupts enabled.
|
|
*/
|
|
local_irq_enable();
|
|
|
|
/*
|
|
* Wait until all coupled cpus have exited idle. There is no risk that
|
|
* a cpu exits and re-enters the ready state because this cpu has
|
|
* already decremented its waiting_count.
|
|
*/
|
|
while (!cpuidle_coupled_no_cpus_ready(coupled))
|
|
cpu_relax();
|
|
|
|
return entered_state;
|
|
}
|
|
|
|
static void cpuidle_coupled_update_online_cpus(struct cpuidle_coupled *coupled)
|
|
{
|
|
cpumask_t cpus;
|
|
cpumask_and(&cpus, cpu_online_mask, &coupled->coupled_cpus);
|
|
coupled->online_count = cpumask_weight(&cpus);
|
|
}
|
|
|
|
/**
|
|
* cpuidle_coupled_register_device - register a coupled cpuidle device
|
|
* @dev: struct cpuidle_device for the current cpu
|
|
*
|
|
* Called from cpuidle_register_device to handle coupled idle init. Finds the
|
|
* cpuidle_coupled struct for this set of coupled cpus, or creates one if none
|
|
* exists yet.
|
|
*/
|
|
int cpuidle_coupled_register_device(struct cpuidle_device *dev)
|
|
{
|
|
int cpu;
|
|
struct cpuidle_device *other_dev;
|
|
struct call_single_data *csd;
|
|
struct cpuidle_coupled *coupled;
|
|
|
|
if (cpumask_empty(&dev->coupled_cpus))
|
|
return 0;
|
|
|
|
for_each_cpu_mask(cpu, dev->coupled_cpus) {
|
|
other_dev = per_cpu(cpuidle_devices, cpu);
|
|
if (other_dev && other_dev->coupled) {
|
|
coupled = other_dev->coupled;
|
|
goto have_coupled;
|
|
}
|
|
}
|
|
|
|
/* No existing coupled info found, create a new one */
|
|
coupled = kzalloc(sizeof(struct cpuidle_coupled), GFP_KERNEL);
|
|
if (!coupled)
|
|
return -ENOMEM;
|
|
|
|
coupled->coupled_cpus = dev->coupled_cpus;
|
|
|
|
have_coupled:
|
|
dev->coupled = coupled;
|
|
if (WARN_ON(!cpumask_equal(&dev->coupled_cpus, &coupled->coupled_cpus)))
|
|
coupled->prevent++;
|
|
|
|
cpuidle_coupled_update_online_cpus(coupled);
|
|
|
|
coupled->refcnt++;
|
|
|
|
csd = &per_cpu(cpuidle_coupled_poke_cb, dev->cpu);
|
|
csd->func = cpuidle_coupled_handle_poke;
|
|
csd->info = (void *)(unsigned long)dev->cpu;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cpuidle_coupled_unregister_device - unregister a coupled cpuidle device
|
|
* @dev: struct cpuidle_device for the current cpu
|
|
*
|
|
* Called from cpuidle_unregister_device to tear down coupled idle. Removes the
|
|
* cpu from the coupled idle set, and frees the cpuidle_coupled_info struct if
|
|
* this was the last cpu in the set.
|
|
*/
|
|
void cpuidle_coupled_unregister_device(struct cpuidle_device *dev)
|
|
{
|
|
struct cpuidle_coupled *coupled = dev->coupled;
|
|
|
|
if (cpumask_empty(&dev->coupled_cpus))
|
|
return;
|
|
|
|
if (--coupled->refcnt)
|
|
kfree(coupled);
|
|
dev->coupled = NULL;
|
|
}
|
|
|
|
/**
|
|
* cpuidle_coupled_prevent_idle - prevent cpus from entering a coupled state
|
|
* @coupled: the struct coupled that contains the cpu that is changing state
|
|
*
|
|
* Disables coupled cpuidle on a coupled set of cpus. Used to ensure that
|
|
* cpu_online_mask doesn't change while cpus are coordinating coupled idle.
|
|
*/
|
|
static void cpuidle_coupled_prevent_idle(struct cpuidle_coupled *coupled)
|
|
{
|
|
int cpu = get_cpu();
|
|
|
|
/* Force all cpus out of the waiting loop. */
|
|
coupled->prevent++;
|
|
cpuidle_coupled_poke_others(cpu, coupled);
|
|
put_cpu();
|
|
while (!cpuidle_coupled_no_cpus_waiting(coupled))
|
|
cpu_relax();
|
|
}
|
|
|
|
/**
|
|
* cpuidle_coupled_allow_idle - allows cpus to enter a coupled state
|
|
* @coupled: the struct coupled that contains the cpu that is changing state
|
|
*
|
|
* Enables coupled cpuidle on a coupled set of cpus. Used to ensure that
|
|
* cpu_online_mask doesn't change while cpus are coordinating coupled idle.
|
|
*/
|
|
static void cpuidle_coupled_allow_idle(struct cpuidle_coupled *coupled)
|
|
{
|
|
int cpu = get_cpu();
|
|
|
|
/*
|
|
* Write barrier ensures readers see the new online_count when they
|
|
* see prevent == 0.
|
|
*/
|
|
smp_wmb();
|
|
coupled->prevent--;
|
|
/* Force cpus out of the prevent loop. */
|
|
cpuidle_coupled_poke_others(cpu, coupled);
|
|
put_cpu();
|
|
}
|
|
|
|
/**
|
|
* cpuidle_coupled_cpu_notify - notifier called during hotplug transitions
|
|
* @nb: notifier block
|
|
* @action: hotplug transition
|
|
* @hcpu: target cpu number
|
|
*
|
|
* Called when a cpu is brought on or offline using hotplug. Updates the
|
|
* coupled cpu set appropriately
|
|
*/
|
|
static int cpuidle_coupled_cpu_notify(struct notifier_block *nb,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
int cpu = (unsigned long)hcpu;
|
|
struct cpuidle_device *dev;
|
|
|
|
switch (action & ~CPU_TASKS_FROZEN) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_DOWN_PREPARE:
|
|
case CPU_ONLINE:
|
|
case CPU_DEAD:
|
|
case CPU_UP_CANCELED:
|
|
case CPU_DOWN_FAILED:
|
|
break;
|
|
default:
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
mutex_lock(&cpuidle_lock);
|
|
|
|
dev = per_cpu(cpuidle_devices, cpu);
|
|
if (!dev || !dev->coupled)
|
|
goto out;
|
|
|
|
switch (action & ~CPU_TASKS_FROZEN) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_DOWN_PREPARE:
|
|
cpuidle_coupled_prevent_idle(dev->coupled);
|
|
break;
|
|
case CPU_ONLINE:
|
|
case CPU_DEAD:
|
|
cpuidle_coupled_update_online_cpus(dev->coupled);
|
|
/* Fall through */
|
|
case CPU_UP_CANCELED:
|
|
case CPU_DOWN_FAILED:
|
|
cpuidle_coupled_allow_idle(dev->coupled);
|
|
break;
|
|
}
|
|
|
|
out:
|
|
mutex_unlock(&cpuidle_lock);
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static struct notifier_block cpuidle_coupled_cpu_notifier = {
|
|
.notifier_call = cpuidle_coupled_cpu_notify,
|
|
};
|
|
|
|
static int __init cpuidle_coupled_init(void)
|
|
{
|
|
return register_cpu_notifier(&cpuidle_coupled_cpu_notifier);
|
|
}
|
|
core_initcall(cpuidle_coupled_init);
|