| /* |
| * coupled.c - helper functions to enter the same idle state on multiple cpus |
| * |
| * Copyright (c) 2011 Google, Inc. |
| * |
| * Author: Colin Cross <ccross@android.com> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
| * more details. |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/cpu.h> |
| #include <linux/cpuidle.h> |
| #include <linux/mutex.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/spinlock.h> |
| |
| #include "cpuidle.h" |
| |
| /** |
| * DOC: Coupled cpuidle states |
| * |
| * On some ARM SMP SoCs (OMAP4460, Tegra 2, and probably more), the |
| * cpus cannot be independently powered down, either due to |
| * sequencing restrictions (on Tegra 2, cpu 0 must be the last to |
| * power down), or due to HW bugs (on OMAP4460, a cpu powering up |
| * will corrupt the gic state unless the other cpu runs a work |
| * around). Each cpu has a power state that it can enter without |
| * coordinating with the other cpu (usually Wait For Interrupt, or |
| * WFI), and one or more "coupled" power states that affect blocks |
| * shared between the cpus (L2 cache, interrupt controller, and |
| * sometimes the whole SoC). Entering a coupled power state must |
| * be tightly controlled on both cpus. |
| * |
| * This file implements a solution, where each cpu will wait in the |
| * WFI state until all cpus are ready to enter a coupled state, at |
| * which point the coupled state function will be called on all |
| * cpus at approximately the same time. |
| * |
| * Once all cpus are ready to enter idle, they are woken by an smp |
| * cross call. At this point, there is a chance that one of the |
| * cpus will find work to do, and choose not to enter idle. A |
| * final pass is needed to guarantee that all cpus will call the |
| * power state enter function at the same time. During this pass, |
| * each cpu will increment the ready counter, and continue once the |
| * ready counter matches the number of online coupled cpus. If any |
| * cpu exits idle, the other cpus will decrement their counter and |
| * retry. |
| * |
| * requested_state stores the deepest coupled idle state each cpu |
| * is ready for. It is assumed that the states are indexed from |
| * shallowest (highest power, lowest exit latency) to deepest |
| * (lowest power, highest exit latency). The requested_state |
| * variable is not locked. It is only written from the cpu that |
| * it stores (or by the on/offlining cpu if that cpu is offline), |
| * and only read after all the cpus are ready for the coupled idle |
| * state are are no longer updating it. |
| * |
| * Three atomic counters are used. alive_count tracks the number |
| * of cpus in the coupled set that are currently or soon will be |
| * online. waiting_count tracks the number of cpus that are in |
| * the waiting loop, in the ready loop, or in the coupled idle state. |
| * ready_count tracks the number of cpus that are in the ready loop |
| * or in the coupled idle state. |
| * |
| * To use coupled cpuidle states, a cpuidle driver must: |
| * |
| * Set struct cpuidle_device.coupled_cpus to the mask of all |
| * coupled cpus, usually the same as cpu_possible_mask if all cpus |
| * are part of the same cluster. The coupled_cpus mask must be |
| * set in the struct cpuidle_device for each cpu. |
| * |
| * Set struct cpuidle_device.safe_state to a state that is not a |
| * coupled state. This is usually WFI. |
| * |
| * Set CPUIDLE_FLAG_COUPLED in struct cpuidle_state.flags for each |
| * state that affects multiple cpus. |
| * |
| * Provide a struct cpuidle_state.enter function for each state |
| * that affects multiple cpus. This function is guaranteed to be |
| * called on all cpus at approximately the same time. The driver |
| * should ensure that the cpus all abort together if any cpu tries |
| * to abort once the function is called. The function should return |
| * with interrupts still disabled. |
| */ |
| |
| /** |
| * struct cpuidle_coupled - data for set of cpus that share a coupled idle state |
| * @coupled_cpus: mask of cpus that are part of the coupled set |
| * @requested_state: array of requested states for cpus in the coupled set |
| * @ready_waiting_counts: combined count of cpus in ready or waiting loops |
| * @online_count: count of cpus that are online |
| * @refcnt: reference count of cpuidle devices that are using this struct |
| * @prevent: flag to prevent coupled idle while a cpu is hotplugging |
| */ |
| struct cpuidle_coupled { |
| cpumask_t coupled_cpus; |
| int requested_state[NR_CPUS]; |
| atomic_t ready_waiting_counts; |
| int online_count; |
| int refcnt; |
| int prevent; |
| }; |
| |
| #define WAITING_BITS 16 |
| #define MAX_WAITING_CPUS (1 << WAITING_BITS) |
| #define WAITING_MASK (MAX_WAITING_CPUS - 1) |
| #define READY_MASK (~WAITING_MASK) |
| |
| #define CPUIDLE_COUPLED_NOT_IDLE (-1) |
| |
| static DEFINE_MUTEX(cpuidle_coupled_lock); |
| static DEFINE_PER_CPU(struct call_single_data, cpuidle_coupled_poke_cb); |
| |
| /* |
| * The cpuidle_coupled_poked_mask mask is used to avoid calling |
| * __smp_call_function_single with the per cpu call_single_data struct already |
| * in use. This prevents a deadlock where two cpus are waiting for each others |
| * call_single_data struct to be available |
| */ |
| static cpumask_t cpuidle_coupled_poked_mask; |
| |
| /** |
| * cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus |
| * @dev: cpuidle_device of the calling cpu |
| * @a: atomic variable to hold the barrier |
| * |
| * No caller to this function will return from this function until all online |
| * cpus in the same coupled group have called this function. Once any caller |
| * has returned from this function, the barrier is immediately available for |
| * reuse. |
| * |
| * The atomic variable a must be initialized to 0 before any cpu calls |
| * this function, will be reset to 0 before any cpu returns from this function. |
| * |
| * Must only be called from within a coupled idle state handler |
| * (state.enter when state.flags has CPUIDLE_FLAG_COUPLED set). |
| * |
| * Provides full smp barrier semantics before and after calling. |
| */ |
| void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a) |
| { |
| int n = dev->coupled->online_count; |
| |
| smp_mb__before_atomic_inc(); |
| atomic_inc(a); |
| |
| while (atomic_read(a) < n) |
| cpu_relax(); |
| |
| if (atomic_inc_return(a) == n * 2) { |
| atomic_set(a, 0); |
| return; |
| } |
| |
| while (atomic_read(a) > n) |
| cpu_relax(); |
| } |
| |
| /** |
| * cpuidle_state_is_coupled - check if a state is part of a coupled set |
| * @dev: struct cpuidle_device for the current cpu |
| * @drv: struct cpuidle_driver for the platform |
| * @state: index of the target state in drv->states |
| * |
| * Returns true if the target state is coupled with cpus besides this one |
| */ |
| bool cpuidle_state_is_coupled(struct cpuidle_device *dev, |
| struct cpuidle_driver *drv, int state) |
| { |
| return drv->states[state].flags & CPUIDLE_FLAG_COUPLED; |
| } |
| |
| /** |
| * cpuidle_coupled_set_ready - mark a cpu as ready |
| * @coupled: the struct coupled that contains the current cpu |
| */ |
| static inline void cpuidle_coupled_set_ready(struct cpuidle_coupled *coupled) |
| { |
| atomic_add(MAX_WAITING_CPUS, &coupled->ready_waiting_counts); |
| } |
| |
| /** |
| * cpuidle_coupled_set_not_ready - mark a cpu as not ready |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Decrements the ready counter, unless the ready (and thus the waiting) counter |
| * is equal to the number of online cpus. Prevents a race where one cpu |
| * decrements the waiting counter and then re-increments it just before another |
| * cpu has decremented its ready counter, leading to the ready counter going |
| * down from the number of online cpus without going through the coupled idle |
| * state. |
| * |
| * Returns 0 if the counter was decremented successfully, -EINVAL if the ready |
| * counter was equal to the number of online cpus. |
| */ |
| static |
| inline int cpuidle_coupled_set_not_ready(struct cpuidle_coupled *coupled) |
| { |
| int all; |
| int ret; |
| |
| all = coupled->online_count || (coupled->online_count << WAITING_BITS); |
| ret = atomic_add_unless(&coupled->ready_waiting_counts, |
| -MAX_WAITING_CPUS, all); |
| |
| return ret ? 0 : -EINVAL; |
| } |
| |
| /** |
| * cpuidle_coupled_no_cpus_ready - check if no cpus in a coupled set are ready |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Returns true if all of the cpus in a coupled set are out of the ready loop. |
| */ |
| static inline int cpuidle_coupled_no_cpus_ready(struct cpuidle_coupled *coupled) |
| { |
| int r = atomic_read(&coupled->ready_waiting_counts) >> WAITING_BITS; |
| return r == 0; |
| } |
| |
| /** |
| * cpuidle_coupled_cpus_ready - check if all cpus in a coupled set are ready |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Returns true if all cpus coupled to this target state are in the ready loop |
| */ |
| static inline bool cpuidle_coupled_cpus_ready(struct cpuidle_coupled *coupled) |
| { |
| int r = atomic_read(&coupled->ready_waiting_counts) >> WAITING_BITS; |
| return r == coupled->online_count; |
| } |
| |
| /** |
| * cpuidle_coupled_cpus_waiting - check if all cpus in a coupled set are waiting |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Returns true if all cpus coupled to this target state are in the wait loop |
| */ |
| static inline bool cpuidle_coupled_cpus_waiting(struct cpuidle_coupled *coupled) |
| { |
| int w = atomic_read(&coupled->ready_waiting_counts) & WAITING_MASK; |
| return w == coupled->online_count; |
| } |
| |
| /** |
| * cpuidle_coupled_no_cpus_waiting - check if no cpus in coupled set are waiting |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Returns true if all of the cpus in a coupled set are out of the waiting loop. |
| */ |
| static inline int cpuidle_coupled_no_cpus_waiting(struct cpuidle_coupled *coupled) |
| { |
| int w = atomic_read(&coupled->ready_waiting_counts) & WAITING_MASK; |
| return w == 0; |
| } |
| |
| /** |
| * cpuidle_coupled_get_state - determine the deepest idle state |
| * @dev: struct cpuidle_device for this cpu |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Returns the deepest idle state that all coupled cpus can enter |
| */ |
| static inline int cpuidle_coupled_get_state(struct cpuidle_device *dev, |
| struct cpuidle_coupled *coupled) |
| { |
| int i; |
| int state = INT_MAX; |
| |
| /* |
| * Read barrier ensures that read of requested_state is ordered after |
| * reads of ready_count. Matches the write barriers |
| * cpuidle_set_state_waiting. |
| */ |
| smp_rmb(); |
| |
| for_each_cpu_mask(i, coupled->coupled_cpus) |
| if (cpu_online(i) && coupled->requested_state[i] < state) |
| state = coupled->requested_state[i]; |
| |
| return state; |
| } |
| |
| static void cpuidle_coupled_poked(void *info) |
| { |
| int cpu = (unsigned long)info; |
| cpumask_clear_cpu(cpu, &cpuidle_coupled_poked_mask); |
| } |
| |
| /** |
| * cpuidle_coupled_poke - wake up a cpu that may be waiting |
| * @cpu: target cpu |
| * |
| * Ensures that the target cpu exits it's waiting idle state (if it is in it) |
| * and will see updates to waiting_count before it re-enters it's waiting idle |
| * state. |
| * |
| * If cpuidle_coupled_poked_mask is already set for the target cpu, that cpu |
| * either has or will soon have a pending IPI that will wake it out of idle, |
| * or it is currently processing the IPI and is not in idle. |
| */ |
| static void cpuidle_coupled_poke(int cpu) |
| { |
| struct call_single_data *csd = &per_cpu(cpuidle_coupled_poke_cb, cpu); |
| |
| if (!cpumask_test_and_set_cpu(cpu, &cpuidle_coupled_poked_mask)) |
| __smp_call_function_single(cpu, csd, 0); |
| } |
| |
| /** |
| * cpuidle_coupled_poke_others - wake up all other cpus that may be waiting |
| * @dev: struct cpuidle_device for this cpu |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Calls cpuidle_coupled_poke on all other online cpus. |
| */ |
| static void cpuidle_coupled_poke_others(int this_cpu, |
| struct cpuidle_coupled *coupled) |
| { |
| int cpu; |
| |
| for_each_cpu_mask(cpu, coupled->coupled_cpus) |
| if (cpu != this_cpu && cpu_online(cpu)) |
| cpuidle_coupled_poke(cpu); |
| } |
| |
| /** |
| * cpuidle_coupled_set_waiting - mark this cpu as in the wait loop |
| * @dev: struct cpuidle_device for this cpu |
| * @coupled: the struct coupled that contains the current cpu |
| * @next_state: the index in drv->states of the requested state for this cpu |
| * |
| * Updates the requested idle state for the specified cpuidle device, |
| * poking all coupled cpus out of idle if necessary to let them see the new |
| * state. |
| */ |
| static void cpuidle_coupled_set_waiting(int cpu, |
| struct cpuidle_coupled *coupled, int next_state) |
| { |
| int w; |
| |
| coupled->requested_state[cpu] = 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. |
| * |
| * The atomic_inc_return provides a write barrier to order the write |
| * to requested_state with the later write that increments ready_count. |
| */ |
| w = atomic_inc_return(&coupled->ready_waiting_counts) & WAITING_MASK; |
| if (w == coupled->online_count) |
| cpuidle_coupled_poke_others(cpu, coupled); |
| } |
| |
| /** |
| * cpuidle_coupled_set_not_waiting - mark this cpu as leaving the wait loop |
| * @dev: struct cpuidle_device for this cpu |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Removes the requested idle state for the specified cpuidle device. |
| */ |
| static void cpuidle_coupled_set_not_waiting(int cpu, |
| struct cpuidle_coupled *coupled) |
| { |
| /* |
| * Decrementing waiting count can race with incrementing it in |
| * cpuidle_coupled_set_waiting, but that's OK. Worst case, some |
| * cpus will increment ready_count and then spin until they |
| * notice that this cpu has cleared it's requested_state. |
| */ |
| atomic_dec(&coupled->ready_waiting_counts); |
| |
| coupled->requested_state[cpu] = CPUIDLE_COUPLED_NOT_IDLE; |
| } |
| |
| /** |
| * cpuidle_coupled_set_done - mark this cpu as leaving the ready loop |
| * @cpu: the current cpu |
| * @coupled: the struct coupled that contains the current cpu |
| * |
| * Marks this cpu as no longer in the ready and waiting loops. Decrements |
| * the waiting count first to prevent another cpu looping back in and seeing |
| * this cpu as waiting just before it exits idle. |
| */ |
| static void cpuidle_coupled_set_done(int cpu, struct cpuidle_coupled *coupled) |
| { |
| cpuidle_coupled_set_not_waiting(cpu, coupled); |
| atomic_sub(MAX_WAITING_CPUS, &coupled->ready_waiting_counts); |
| } |
| |
| /** |
| * cpuidle_coupled_clear_pokes - spin until the poke interrupt is processed |
| * @cpu - this cpu |
| * |
| * Turns on interrupts and spins until any outstanding poke interrupts have |
| * been processed and the poke bit has been cleared. |
| * |
| * Other interrupts may also be processed while interrupts are enabled, so |
| * need_resched() must be tested after turning interrupts off again to make sure |
| * the interrupt didn't schedule work that should take the cpu out of idle. |
| * |
| * Returns 0 if need_resched was false, -EINTR if need_resched was true. |
| */ |
| static int cpuidle_coupled_clear_pokes(int cpu) |
| { |
| local_irq_enable(); |
| while (cpumask_test_cpu(cpu, &cpuidle_coupled_poked_mask)) |
| cpu_relax(); |
| local_irq_disable(); |
| |
| return need_resched() ? -EINTR : 0; |
| } |
| |
| /** |
| * cpuidle_enter_state_coupled - attempt to enter a state with coupled cpus |
| * @dev: struct cpuidle_device for the current cpu |
| * @drv: struct cpuidle_driver for the platform |
| * @next_state: index of the requested state in drv->states |
| * |
| * Coordinate with coupled cpus to enter the target state. This is a two |
| * stage process. In the first stage, the cpus are operating independently, |
| * and may call into cpuidle_enter_state_coupled at completely different times. |
| * To save as much power as possible, the first cpus to call this function will |
| * go to an intermediate state (the cpuidle_device's safe state), and wait for |
| * all the other cpus to call this function. Once all coupled cpus are idle, |
| * the second stage will start. Each coupled cpu will spin until all cpus have |
| * guaranteed that they will call the target_state. |
| * |
| * This function must be called with interrupts disabled. It may enable |
| * interrupts while preparing for idle, and it will always return with |
| * interrupts enabled. |
| */ |
| int cpuidle_enter_state_coupled(struct cpuidle_device *dev, |
| struct cpuidle_driver *drv, int next_state) |
| { |
| int entered_state = -1; |
| struct cpuidle_coupled *coupled = dev->coupled; |
| |
| if (!coupled) |
| return -EINVAL; |
| |
| while (coupled->prevent) { |
| if (cpuidle_coupled_clear_pokes(dev->cpu)) { |
| local_irq_enable(); |
| return entered_state; |
| } |
| entered_state = cpuidle_enter_state(dev, drv, |
| dev->safe_state_index); |
| } |
| |
| /* Read barrier ensures online_count is read after prevent is cleared */ |
| smp_rmb(); |
| |
| cpuidle_coupled_set_waiting(dev->cpu, coupled, next_state); |
| |
| retry: |
| /* |
| * Wait for all coupled cpus to be idle, using the deepest state |
| * allowed for a single cpu. |
| */ |
| while (!cpuidle_coupled_cpus_waiting(coupled)) { |
| if (cpuidle_coupled_clear_pokes(dev->cpu)) { |
| 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); |
| } |
| |
| if (cpuidle_coupled_clear_pokes(dev->cpu)) { |
| cpuidle_coupled_set_not_waiting(dev->cpu, coupled); |
| goto out; |
| } |
| |
| /* |
| * 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(); |
| } |
| |
| /* 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_poked; |
| 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); |