v4.19.13 snapshot.
diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c
new file mode 100644
index 0000000..147f38e
--- /dev/null
+++ b/drivers/cpuidle/coupled.c
@@ -0,0 +1,800 @@
+/*
+ * 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;
+ atomic_t abort_barrier;
+ 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_PER_CPU(call_single_data_t, cpuidle_coupled_poke_cb);
+
+/*
+ * The cpuidle_coupled_poke_pending mask is used to avoid calling
+ * __smp_call_function_single with the per cpu call_single_data_t struct already
+ * in use. This prevents a deadlock where two cpus are waiting for each others
+ * call_single_data_t struct to be available
+ */
+static cpumask_t cpuidle_coupled_poke_pending;
+
+/*
+ * The cpuidle_coupled_poked mask is used to ensure that each cpu has been poked
+ * once to minimize entering the ready loop with a poke pending, which would
+ * require aborting and retrying.
+ */
+static cpumask_t cpuidle_coupled_poked;
+
+/**
+ * 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 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();
+ 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
+ * @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_driver *drv, int state)
+{
+ return drv->states[state].flags & CPUIDLE_FLAG_COUPLED;
+}
+
+/**
+ * cpuidle_coupled_state_verify - check if the coupled states are correctly set.
+ * @drv: struct cpuidle_driver for the platform
+ *
+ * Returns 0 for valid state values, a negative error code otherwise:
+ * * -EINVAL if any coupled state(safe_state_index) is wrongly set.
+ */
+int cpuidle_coupled_state_verify(struct cpuidle_driver *drv)
+{
+ int i;
+
+ for (i = drv->state_count - 1; i >= 0; i--) {
+ if (cpuidle_state_is_coupled(drv, i) &&
+ (drv->safe_state_index == i ||
+ drv->safe_state_index < 0 ||
+ drv->safe_state_index >= drv->state_count))
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/**
+ * 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(i, &coupled->coupled_cpus)
+ if (cpu_online(i) && coupled->requested_state[i] < state)
+ state = coupled->requested_state[i];
+
+ return state;
+}
+
+static void cpuidle_coupled_handle_poke(void *info)
+{
+ int cpu = (unsigned long)info;
+ cpumask_set_cpu(cpu, &cpuidle_coupled_poked);
+ cpumask_clear_cpu(cpu, &cpuidle_coupled_poke_pending);
+}
+
+/**
+ * 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)
+{
+ call_single_data_t *csd = &per_cpu(cpuidle_coupled_poke_cb, cpu);
+
+ if (!cpumask_test_and_set_cpu(cpu, &cpuidle_coupled_poke_pending))
+ smp_call_function_single_async(cpu, csd);
+}
+
+/**
+ * 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(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.
+ * Returns the number of waiting cpus.
+ */
+static int cpuidle_coupled_set_waiting(int cpu,
+ struct cpuidle_coupled *coupled, int next_state)
+{
+ coupled->requested_state[cpu] = next_state;
+
+ /*
+ * The atomic_inc_return provides a write barrier to order the write
+ * to requested_state with the later write that increments ready_count.
+ */
+ return atomic_inc_return(&coupled->ready_waiting_counts) & WAITING_MASK;
+}
+
+/**
+ * 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 this function returns to make sure
+ * the interrupt didn't schedule work that should take the cpu out of idle.
+ *
+ * Returns 0 if no poke was pending, 1 if a poke was cleared.
+ */
+static int cpuidle_coupled_clear_pokes(int cpu)
+{
+ if (!cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending))
+ return 0;
+
+ local_irq_enable();
+ while (cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending))
+ cpu_relax();
+ local_irq_disable();
+
+ return 1;
+}
+
+static bool cpuidle_coupled_any_pokes_pending(struct cpuidle_coupled *coupled)
+{
+ cpumask_t cpus;
+ int ret;
+
+ cpumask_and(&cpus, cpu_online_mask, &coupled->coupled_cpus);
+ ret = cpumask_and(&cpus, &cpuidle_coupled_poke_pending, &cpus);
+
+ return ret;
+}
+
+/**
+ * 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;
+ int w;
+
+ 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,
+ drv->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,
+ drv->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;
+ call_single_data_t *csd;
+ struct cpuidle_coupled *coupled;
+
+ if (cpumask_empty(&dev->coupled_cpus))
+ return 0;
+
+ for_each_cpu(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();
+}
+
+static int coupled_cpu_online(unsigned int cpu)
+{
+ struct cpuidle_device *dev;
+
+ mutex_lock(&cpuidle_lock);
+
+ dev = per_cpu(cpuidle_devices, cpu);
+ if (dev && dev->coupled) {
+ cpuidle_coupled_update_online_cpus(dev->coupled);
+ cpuidle_coupled_allow_idle(dev->coupled);
+ }
+
+ mutex_unlock(&cpuidle_lock);
+ return 0;
+}
+
+static int coupled_cpu_up_prepare(unsigned int cpu)
+{
+ struct cpuidle_device *dev;
+
+ mutex_lock(&cpuidle_lock);
+
+ dev = per_cpu(cpuidle_devices, cpu);
+ if (dev && dev->coupled)
+ cpuidle_coupled_prevent_idle(dev->coupled);
+
+ mutex_unlock(&cpuidle_lock);
+ return 0;
+}
+
+static int __init cpuidle_coupled_init(void)
+{
+ int ret;
+
+ ret = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_COUPLED_PREPARE,
+ "cpuidle/coupled:prepare",
+ coupled_cpu_up_prepare,
+ coupled_cpu_online);
+ if (ret)
+ return ret;
+ ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "cpuidle/coupled:online",
+ coupled_cpu_online,
+ coupled_cpu_up_prepare);
+ if (ret < 0)
+ cpuhp_remove_state_nocalls(CPUHP_CPUIDLE_COUPLED_PREPARE);
+ return ret;
+}
+core_initcall(cpuidle_coupled_init);