// SPDX-License-Identifier: GPL-2.0
/*
 *  cpuidle-powernv - idle state cpuidle driver.
 *  Adapted from drivers/cpuidle/cpuidle-pseries
 *
 */

#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 <linux/clockchips.h>
#include <linux/of.h>
#include <linux/slab.h>

#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/opal.h>
#include <asm/runlatch.h>
#include <asm/cpuidle.h>

/*
 * Expose only those Hardware idle states via the cpuidle framework
 * that have latency value below POWERNV_THRESHOLD_LATENCY_NS.
 */
#define POWERNV_THRESHOLD_LATENCY_NS 200000

static struct cpuidle_driver powernv_idle_driver = {
        .name             = "powernv_idle",
        .owner            = THIS_MODULE,
};

static int max_idle_state __read_mostly;
static struct cpuidle_state *cpuidle_state_table __read_mostly;

struct stop_psscr_table {
        u64 val;
        u64 mask;
};

static struct stop_psscr_table stop_psscr_table[CPUIDLE_STATE_MAX] __read_mostly;

static u64 default_snooze_timeout __read_mostly;
static bool snooze_timeout_en __read_mostly;

static u64 get_snooze_timeout(struct cpuidle_device *dev,
                              struct cpuidle_driver *drv,
                              int index)
{
        int i;

        if (unlikely(!snooze_timeout_en))
                return default_snooze_timeout;

        for (i = index + 1; i < drv->state_count; i++) {
                if (dev->states_usage[i].disable)
                        continue;

                return drv->states[i].target_residency * tb_ticks_per_usec;
        }

        return default_snooze_timeout;
}

static int snooze_loop(struct cpuidle_device *dev,
                        struct cpuidle_driver *drv,
                        int index)
{
        u64 snooze_exit_time;

        set_thread_flag(TIF_POLLING_NRFLAG);

        local_irq_enable();

        snooze_exit_time = get_tb() + get_snooze_timeout(dev, drv, index);
        dev->poll_time_limit = false;
        ppc64_runlatch_off();
        HMT_very_low();
        while (!need_resched()) {
                if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
                        /*
                         * Task has not woken up but we are exiting the polling
                         * loop anyway. Require a barrier after polling is
                         * cleared to order subsequent test of need_resched().
                         */
                        clear_thread_flag(TIF_POLLING_NRFLAG);
                        dev->poll_time_limit = true;
                        smp_mb();
                        break;
                }
        }

        HMT_medium();
        ppc64_runlatch_on();
        clear_thread_flag(TIF_POLLING_NRFLAG);

        local_irq_disable();

        return index;
}

static int nap_loop(struct cpuidle_device *dev,
                        struct cpuidle_driver *drv,
                        int index)
{
        power7_idle_type(PNV_THREAD_NAP);

        return index;
}

/* Register for fastsleep only in oneshot mode of broadcast */
#ifdef CONFIG_TICK_ONESHOT
static int fastsleep_loop(struct cpuidle_device *dev,
                                struct cpuidle_driver *drv,
                                int index)
{
        unsigned long old_lpcr = mfspr(SPRN_LPCR);
        unsigned long new_lpcr;

        if (unlikely(system_state < SYSTEM_RUNNING))
                return index;

        new_lpcr = old_lpcr;
        /* Do not exit powersave upon decrementer as we've setup the timer
         * offload.
         */
        new_lpcr &= ~LPCR_PECE1;

        mtspr(SPRN_LPCR, new_lpcr);

        power7_idle_type(PNV_THREAD_SLEEP);

        mtspr(SPRN_LPCR, old_lpcr);

        return index;
}
#endif

static int stop_loop(struct cpuidle_device *dev,
                     struct cpuidle_driver *drv,
                     int index)
{
        arch300_idle_type(stop_psscr_table[index].val,
                         stop_psscr_table[index].mask);
        return index;
}

/*
 * States for dedicated partition case.
 */
static struct cpuidle_state powernv_states[CPUIDLE_STATE_MAX] = {
        { /* Snooze */
                .name = "snooze",
                .desc = "snooze",
                .exit_latency = 0,
                .target_residency = 0,
                .enter = snooze_loop,
                .flags = CPUIDLE_FLAG_POLLING },
};

static int powernv_cpuidle_cpu_online(unsigned int cpu)
{
        struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);

        if (dev && cpuidle_get_driver()) {
                cpuidle_pause_and_lock();
                cpuidle_enable_device(dev);
                cpuidle_resume_and_unlock();
        }
        return 0;
}

static int powernv_cpuidle_cpu_dead(unsigned int cpu)
{
        struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);

        if (dev && cpuidle_get_driver()) {
                cpuidle_pause_and_lock();
                cpuidle_disable_device(dev);
                cpuidle_resume_and_unlock();
        }
        return 0;
}

/*
 * powernv_cpuidle_driver_init()
 */
static int powernv_cpuidle_driver_init(void)
{
        int idle_state;
        struct cpuidle_driver *drv = &powernv_idle_driver;

        drv->state_count = 0;

        for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
                /* 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;
        }

        /*
         * On the PowerNV platform cpu_present may be less than cpu_possible in
         * cases when firmware detects the CPU, but it is not available to the
         * OS.  If CONFIG_HOTPLUG_CPU=n, then such CPUs are not hotplugable at
         * run time and hence cpu_devices are not created for those CPUs by the
         * generic topology_init().
         *
         * drv->cpumask defaults to cpu_possible_mask in
         * __cpuidle_driver_init().  This breaks cpuidle on PowerNV where
         * cpu_devices are not created for CPUs in cpu_possible_mask that
         * cannot be hot-added later at run time.
         *
         * Trying cpuidle_register_device() on a CPU without a cpu_device is
         * incorrect, so pass a correct CPU mask to the generic cpuidle driver.
         */

        drv->cpumask = (struct cpumask *)cpu_present_mask;

        return 0;
}

static inline void add_powernv_state(int index, const char *name,
                                     unsigned int flags,
                                     int (*idle_fn)(struct cpuidle_device *,
                                                    struct cpuidle_driver *,
                                                    int),
                                     unsigned int target_residency,
                                     unsigned int exit_latency,
                                     u64 psscr_val, u64 psscr_mask)
{
        strscpy(powernv_states[index].name, name, CPUIDLE_NAME_LEN);
        strscpy(powernv_states[index].desc, name, CPUIDLE_NAME_LEN);
        powernv_states[index].flags = flags;
        powernv_states[index].target_residency = target_residency;
        powernv_states[index].exit_latency = exit_latency;
        powernv_states[index].enter = idle_fn;
        /* For power8 and below psscr_* will be 0 */
        stop_psscr_table[index].val = psscr_val;
        stop_psscr_table[index].mask = psscr_mask;
}

extern u32 pnv_get_supported_cpuidle_states(void);
static int powernv_add_idle_states(void)
{
        int nr_idle_states = 1; /* Snooze */
        int dt_idle_states;
        u32 has_stop_states = 0;
        int i;
        u32 supported_flags = pnv_get_supported_cpuidle_states();


        /* Currently we have snooze statically defined */
        if (nr_pnv_idle_states <= 0) {
                pr_warn("cpuidle-powernv : Only Snooze is available\n");
                goto out;
        }

        /* TODO: Count only states which are eligible for cpuidle */
        dt_idle_states = nr_pnv_idle_states;

        /*
         * Since snooze is used as first idle state, max idle states allowed is
         * CPUIDLE_STATE_MAX -1
         */
        if (nr_pnv_idle_states > CPUIDLE_STATE_MAX - 1) {
                pr_warn("cpuidle-powernv: discovered idle states more than allowed");
                dt_idle_states = CPUIDLE_STATE_MAX - 1;
        }

        /*
         * If the idle states use stop instruction, probe for psscr values
         * and psscr mask which are necessary to specify required stop level.
         */
        has_stop_states = (pnv_idle_states[0].flags &
                           (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP));

        for (i = 0; i < dt_idle_states; i++) {
                unsigned int exit_latency, target_residency;
                bool stops_timebase = false;
                struct pnv_idle_states_t *state = &pnv_idle_states[i];

                /*
                 * Skip the platform idle state whose flag isn't in
                 * the supported_cpuidle_states flag mask.
                 */
                if ((state->flags & supported_flags) != state->flags)
                        continue;
                /*
                 * If an idle state has exit latency beyond
                 * POWERNV_THRESHOLD_LATENCY_NS then don't use it
                 * in cpu-idle.
                 */
                if (state->latency_ns > POWERNV_THRESHOLD_LATENCY_NS)
                        continue;
                /*
                 * Firmware passes residency and latency values in ns.
                 * cpuidle expects it in us.
                 */
                exit_latency = DIV_ROUND_UP(state->latency_ns, 1000);
                target_residency = DIV_ROUND_UP(state->residency_ns, 1000);

                if (has_stop_states && !(state->valid))
                                continue;

                if (state->flags & OPAL_PM_TIMEBASE_STOP)
                        stops_timebase = true;

                if (state->flags & OPAL_PM_NAP_ENABLED) {
                        /* Add NAP state */
                        add_powernv_state(nr_idle_states, "Nap",
                                          CPUIDLE_FLAG_NONE, nap_loop,
                                          target_residency, exit_latency, 0, 0);
                } else if (has_stop_states && !stops_timebase) {
                        add_powernv_state(nr_idle_states, state->name,
                                          CPUIDLE_FLAG_NONE, stop_loop,
                                          target_residency, exit_latency,
                                          state->psscr_val,
                                          state->psscr_mask);
                }

                /*
                 * All cpuidle states with CPUIDLE_FLAG_TIMER_STOP set must come
                 * within this config dependency check.
                 */
#ifdef CONFIG_TICK_ONESHOT
                else if (state->flags & OPAL_PM_SLEEP_ENABLED ||
                         state->flags & OPAL_PM_SLEEP_ENABLED_ER1) {
                        /* Add FASTSLEEP state */
                        add_powernv_state(nr_idle_states, "FastSleep",
                                          CPUIDLE_FLAG_TIMER_STOP,
                                          fastsleep_loop,
                                          target_residency, exit_latency, 0, 0);
                } else if (has_stop_states && stops_timebase) {
                        add_powernv_state(nr_idle_states, state->name,
                                          CPUIDLE_FLAG_TIMER_STOP, stop_loop,
                                          target_residency, exit_latency,
                                          state->psscr_val,
                                          state->psscr_mask);
                }
#endif
                else
                        continue;
                nr_idle_states++;
        }
out:
        return nr_idle_states;
}

/*
 * powernv_idle_probe()
 * Choose state table for shared versus dedicated partition
 */
static int powernv_idle_probe(void)
{
        if (cpuidle_disable != IDLE_NO_OVERRIDE)
                return -ENODEV;

        if (firmware_has_feature(FW_FEATURE_OPAL)) {
                cpuidle_state_table = powernv_states;
                /* Device tree can indicate more idle states */
                max_idle_state = powernv_add_idle_states();
                default_snooze_timeout = TICK_USEC * tb_ticks_per_usec;
                if (max_idle_state > 1)
                        snooze_timeout_en = true;
        } else
                return -ENODEV;

        return 0;
}

static int __init powernv_processor_idle_init(void)
{
        int retval;

        retval = powernv_idle_probe();
        if (retval)
                return retval;

        powernv_cpuidle_driver_init();
        retval = cpuidle_register(&powernv_idle_driver, NULL);
        if (retval) {
                printk(KERN_DEBUG "Registration of powernv driver failed.\n");
                return retval;
        }

        retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
                                           "cpuidle/powernv:online",
                                           powernv_cpuidle_cpu_online, NULL);
        WARN_ON(retval < 0);
        retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
                                           "cpuidle/powernv:dead", NULL,
                                           powernv_cpuidle_cpu_dead);
        WARN_ON(retval < 0);
        printk(KERN_DEBUG "powernv_idle_driver registered\n");
        return 0;
}

device_initcall(powernv_processor_idle_init);