processor_idle.c

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/*
 *  processor_idle - idle state cpuidle driver.
 *  Adapted from drivers/idle/intel_idle.c and
 *  drivers/acpi/processor_idle.c
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
#include <linux/notifier.h>

#include <asm/paca.h>
#include <asm/reg.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/runlatch.h>

#include "plpar_wrappers.h"
#include "pseries.h"

struct cpuidle_driver pseries_idle_driver = {
    .name =     "pseries_idle",
    .owner =    THIS_MODULE,
};

#define MAX_IDLE_STATE_COUNT    2

static int max_idle_state = MAX_IDLE_STATE_COUNT - 1;
static struct cpuidle_device __percpu *pseries_cpuidle_devices;
static struct cpuidle_state *cpuidle_state_table;

static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before)
{

    *kt_before = ktime_get_real();
    *in_purr = mfspr(SPRN_PURR);
    /*
     * Indicate to the HV that we are idle. Now would be
     * a good time to find other work to dispatch.
     */
    get_lppaca()->idle = 1;
}

static inline  s64 idle_loop_epilog(unsigned long in_purr, ktime_t kt_before)
{
    get_lppaca()->wait_state_cycles += mfspr(SPRN_PURR) - in_purr;
    get_lppaca()->idle = 0;

    return ktime_to_us(ktime_sub(ktime_get_real(), kt_before));
}

static int snooze_loop(struct cpuidle_device *dev,
            struct cpuidle_driver *drv,
            int index)
{
    unsigned long in_purr;
    ktime_t kt_before;
    int cpu = dev->cpu;

    idle_loop_prolog(&in_purr, &kt_before);
    local_irq_enable();
    set_thread_flag(TIF_POLLING_NRFLAG);

    while ((!need_resched()) && cpu_online(cpu)) {
        ppc64_runlatch_off();
        HMT_low();
        HMT_very_low();
    }

    HMT_medium();
    clear_thread_flag(TIF_POLLING_NRFLAG);
    smp_mb();

    dev->last_residency =
        (int)idle_loop_epilog(in_purr, kt_before);
    return index;
}

static void check_and_cede_processor(void)
{
    /*
     * Ensure our interrupt state is properly tracked,
     * also checks if no interrupt has occurred while we
     * were soft-disabled
     */
    if (prep_irq_for_idle()) {
        cede_processor();
#ifdef CONFIG_TRACE_IRQFLAGS
        /* Ensure that H_CEDE returns with IRQs on */
        if (WARN_ON(!(mfmsr() & MSR_EE)))
            __hard_irq_enable();
#endif
    }
}

static int dedicated_cede_loop(struct cpuidle_device *dev,
                struct cpuidle_driver *drv,
                int index)
{
    unsigned long in_purr;
    ktime_t kt_before;

    idle_loop_prolog(&in_purr, &kt_before);
    get_lppaca()->donate_dedicated_cpu = 1;

    ppc64_runlatch_off();
    HMT_medium();
    check_and_cede_processor();

    get_lppaca()->donate_dedicated_cpu = 0;
    dev->last_residency =
        (int)idle_loop_epilog(in_purr, kt_before);
    return index;
}

static int shared_cede_loop(struct cpuidle_device *dev,
            struct cpuidle_driver *drv,
            int index)
{
    unsigned long in_purr;
    ktime_t kt_before;

    idle_loop_prolog(&in_purr, &kt_before);

    /*
     * Yield the processor to the hypervisor.  We return if
     * an external interrupt occurs (which are driven prior
     * to returning here) or if a prod occurs from another
     * processor. When returning here, external interrupts
     * are enabled.
     */
    check_and_cede_processor();

    dev->last_residency =
        (int)idle_loop_epilog(in_purr, kt_before);
    return index;
}

/*
 * States for dedicated partition case.
 */
static struct cpuidle_state dedicated_states[MAX_IDLE_STATE_COUNT] = {
    { /* Snooze */
        .name = "snooze",
        .desc = "snooze",
        .flags = CPUIDLE_FLAG_TIME_VALID,
        .exit_latency = 0,
        .target_residency = 0,
        .enter = &snooze_loop },
    { /* CEDE */
        .name = "CEDE",
        .desc = "CEDE",
        .flags = CPUIDLE_FLAG_TIME_VALID,
        .exit_latency = 10,
        .target_residency = 100,
        .enter = &dedicated_cede_loop },
};

/*
 * States for shared partition case.
 */
static struct cpuidle_state shared_states[MAX_IDLE_STATE_COUNT] = {
    { /* Shared Cede */
        .name = "Shared Cede",
        .desc = "Shared Cede",
        .flags = CPUIDLE_FLAG_TIME_VALID,
        .exit_latency = 0,
        .target_residency = 0,
        .enter = &shared_cede_loop },
};

void update_smt_snooze_delay(int cpu, int residency)
{
    struct cpuidle_driver *drv = cpuidle_get_driver();
    struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);

    if (cpuidle_state_table != dedicated_states)
        return;

    if (residency < 0) {
        /* Disable the Nap state on that cpu */
        if (dev)
            dev->states_usage[1].disable = 1;
    } else
        if (drv)
            drv->states[1].target_residency = residency;
}

static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
            unsigned long action, void *hcpu)
{
    int hotcpu = (unsigned long)hcpu;
    struct cpuidle_device *dev =
            per_cpu_ptr(pseries_cpuidle_devices, hotcpu);

    if (dev && cpuidle_get_driver()) {
        switch (action) {
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
            cpuidle_pause_and_lock();
            cpuidle_enable_device(dev);
            cpuidle_resume_and_unlock();
            break;

        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
            cpuidle_pause_and_lock();
            cpuidle_disable_device(dev);
            cpuidle_resume_and_unlock();
            break;

        default:
            return NOTIFY_DONE;
        }
    }
    return NOTIFY_OK;
}

static struct notifier_block setup_hotplug_notifier = {
    .notifier_call = pseries_cpuidle_add_cpu_notifier,
};

/*
 * pseries_cpuidle_driver_init()
 */
static int pseries_cpuidle_driver_init(void)
{
    int idle_state;
    struct cpuidle_driver *drv = &pseries_idle_driver;

    drv->state_count = 0;

    for (idle_state = 0; idle_state < MAX_IDLE_STATE_COUNT; ++idle_state) {

        if (idle_state > max_idle_state)
            break;

        /* is the state not enabled? */
        if (cpuidle_state_table[idle_state].enter == NULL)
            continue;

        drv->states[drv->state_count] = /* structure copy */
            cpuidle_state_table[idle_state];

        drv->state_count += 1;
    }

    return 0;
}

/* pseries_idle_devices_uninit(void)
 * unregister cpuidle devices and de-allocate memory
 */
static void pseries_idle_devices_uninit(void)
{
    int i;
    struct cpuidle_device *dev;

    for_each_possible_cpu(i) {
        dev = per_cpu_ptr(pseries_cpuidle_devices, i);
        cpuidle_unregister_device(dev);
    }

    free_percpu(pseries_cpuidle_devices);
    return;
}

/* pseries_idle_devices_init()
 * allocate, initialize and register cpuidle device
 */
static int pseries_idle_devices_init(void)
{
    int i;
    struct cpuidle_driver *drv = &pseries_idle_driver;
    struct cpuidle_device *dev;

    pseries_cpuidle_devices = alloc_percpu(struct cpuidle_device);
    if (pseries_cpuidle_devices == NULL)
        return -ENOMEM;

    for_each_possible_cpu(i) {
        dev = per_cpu_ptr(pseries_cpuidle_devices, i);
        dev->state_count = drv->state_count;
        dev->cpu = i;
        if (cpuidle_register_device(dev)) {
            printk(KERN_DEBUG \
                "cpuidle_register_device %d failed!\n", i);
            return -EIO;
        }
    }

    return 0;
}

/*
 * pseries_idle_probe()
 * Choose state table for shared versus dedicated partition
 */
static int pseries_idle_probe(void)
{

    if (!firmware_has_feature(FW_FEATURE_SPLPAR))
        return -ENODEV;

    if (cpuidle_disable != IDLE_NO_OVERRIDE)
        return -ENODEV;

    if (max_idle_state == 0) {
        printk(KERN_DEBUG "pseries processor idle disabled.\n");
        return -EPERM;
    }

    if (get_lppaca()->shared_proc)
        cpuidle_state_table = shared_states;
    else
        cpuidle_state_table = dedicated_states;

    return 0;
}

static int __init pseries_processor_idle_init(void)
{
    int retval;

    retval = pseries_idle_probe();
    if (retval)
        return retval;

    pseries_cpuidle_driver_init();
    retval = cpuidle_register_driver(&pseries_idle_driver);
    if (retval) {
        printk(KERN_DEBUG "Registration of pseries driver failed.\n");
        return retval;
    }

    retval = pseries_idle_devices_init();
    if (retval) {
        pseries_idle_devices_uninit();
        cpuidle_unregister_driver(&pseries_idle_driver);
        return retval;
    }

    register_cpu_notifier(&setup_hotplug_notifier);
    printk(KERN_DEBUG "pseries_idle_driver registered\n");

    return 0;
}

static void __exit pseries_processor_idle_exit(void)
{

    unregister_cpu_notifier(&setup_hotplug_notifier);
    pseries_idle_devices_uninit();
    cpuidle_unregister_driver(&pseries_idle_driver);

    return;
}

module_init(pseries_processor_idle_init);
module_exit(pseries_processor_idle_exit);

MODULE_AUTHOR("Deepthi Dharwar <[email protected]>");
MODULE_DESCRIPTION("Cpuidle driver for POWER");
MODULE_LICENSE("GPL");