// SPDX-License-Identifier: GPL-2.0-only
/*
 * PSCI CPU idle driver.
 *
 * Copyright (C) 2019 ARM Ltd.
 * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
 */

#define pr_fmt(fmt) "CPUidle PSCI: " fmt

#include <linux/cpuhotplug.h>
#include <linux/cpu_cooling.h>
#include <linux/cpuidle.h>
#include <linux/cpumask.h>
#include <linux/cpu_pm.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/device/faux.h>
#include <linux/psci.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/syscore_ops.h>

#include <asm/cpuidle.h>
#include <trace/events/power.h>

#include "cpuidle-psci.h"
#include "dt_idle_states.h"
#include "dt_idle_genpd.h"

struct psci_cpuidle_data {
        u32 *psci_states;
        struct device *dev;
};

struct psci_cpuidle_domain_state {
        struct generic_pm_domain *pd;
        unsigned int state_idx;
        u32 state;
};

static DEFINE_PER_CPU_READ_MOSTLY(struct psci_cpuidle_data, psci_cpuidle_data);
static DEFINE_PER_CPU(struct psci_cpuidle_domain_state, psci_domain_state);
static bool psci_cpuidle_use_syscore;

void psci_set_domain_state(struct generic_pm_domain *pd, unsigned int state_idx,
                           u32 state)
{
        struct psci_cpuidle_domain_state *ds = this_cpu_ptr(&psci_domain_state);

        ds->pd = pd;
        ds->state_idx = state_idx;
        ds->state = state;
}

static inline void psci_clear_domain_state(void)
{
        __this_cpu_write(psci_domain_state.state, 0);
}

static __cpuidle int __psci_enter_domain_idle_state(struct cpuidle_device *dev,
                                                    struct cpuidle_driver *drv, int idx,
                                                    bool s2idle)
{
        struct psci_cpuidle_data *data = this_cpu_ptr(&psci_cpuidle_data);
        u32 *states = data->psci_states;
        struct device *pd_dev = data->dev;
        struct psci_cpuidle_domain_state *ds;
        u32 state = states[idx];
        int ret;

        ret = cpu_pm_enter();
        if (ret)
                return -1;

        /* Do runtime PM to manage a hierarchical CPU toplogy. */
        if (s2idle)
                dev_pm_genpd_suspend(pd_dev);
        else
                pm_runtime_put_sync_suspend(pd_dev);

        ds = this_cpu_ptr(&psci_domain_state);
        if (ds->state)
                state = ds->state;

        trace_psci_domain_idle_enter(dev->cpu, state, s2idle);
        ret = psci_cpu_suspend_enter(state) ? -1 : idx;
        trace_psci_domain_idle_exit(dev->cpu, state, s2idle);

        if (s2idle)
                dev_pm_genpd_resume(pd_dev);
        else
                pm_runtime_get_sync(pd_dev);

        cpu_pm_exit();

        /* Correct domain-idlestate statistics if we failed to enter. */
        if (ret == -1 && ds->state)
                pm_genpd_inc_rejected(ds->pd, ds->state_idx);

        /* Clear the domain state to start fresh when back from idle. */
        psci_clear_domain_state();
        return ret;
}

static int psci_enter_domain_idle_state(struct cpuidle_device *dev,
                                        struct cpuidle_driver *drv, int idx)
{
        return __psci_enter_domain_idle_state(dev, drv, idx, false);
}

static int psci_enter_s2idle_domain_idle_state(struct cpuidle_device *dev,
                                               struct cpuidle_driver *drv,
                                               int idx)
{
        return __psci_enter_domain_idle_state(dev, drv, idx, true);
}

static int psci_idle_cpuhp_up(unsigned int cpu)
{
        struct device *pd_dev = __this_cpu_read(psci_cpuidle_data.dev);

        if (pd_dev) {
                if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                        pm_runtime_get_sync(pd_dev);
                else
                        dev_pm_genpd_resume(pd_dev);
        }

        return 0;
}

static int psci_idle_cpuhp_down(unsigned int cpu)
{
        struct device *pd_dev = __this_cpu_read(psci_cpuidle_data.dev);

        if (pd_dev) {
                if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                        pm_runtime_put_sync(pd_dev);
                else
                        dev_pm_genpd_suspend(pd_dev);

                /* Clear domain state to start fresh at next online. */
                psci_clear_domain_state();
        }

        return 0;
}

static void psci_idle_syscore_switch(bool suspend)
{
        bool cleared = false;
        struct device *dev;
        int cpu;

        for_each_possible_cpu(cpu) {
                dev = per_cpu_ptr(&psci_cpuidle_data, cpu)->dev;

                if (dev && suspend) {
                        dev_pm_genpd_suspend(dev);
                } else if (dev) {
                        dev_pm_genpd_resume(dev);

                        /* Account for userspace having offlined a CPU. */
                        if (pm_runtime_status_suspended(dev))
                                pm_runtime_set_active(dev);

                        /* Clear domain state to re-start fresh. */
                        if (!cleared) {
                                psci_clear_domain_state();
                                cleared = true;
                        }
                }
        }
}

static int psci_idle_syscore_suspend(void *data)
{
        psci_idle_syscore_switch(true);
        return 0;
}

static void psci_idle_syscore_resume(void *data)
{
        psci_idle_syscore_switch(false);
}

static const struct syscore_ops psci_idle_syscore_ops = {
        .suspend = psci_idle_syscore_suspend,
        .resume = psci_idle_syscore_resume,
};

static struct syscore psci_idle_syscore = {
        .ops = &psci_idle_syscore_ops,
};

static void psci_idle_init_syscore(void)
{
        if (psci_cpuidle_use_syscore)
                register_syscore(&psci_idle_syscore);
}

static void psci_idle_init_cpuhp(void)
{
        int err;

        err = cpuhp_setup_state_nocalls(CPUHP_AP_CPU_PM_STARTING,
                                        "cpuidle/psci:online",
                                        psci_idle_cpuhp_up,
                                        psci_idle_cpuhp_down);
        if (err)
                pr_warn("Failed %d while setup cpuhp state\n", err);
}

static __cpuidle int psci_enter_idle_state(struct cpuidle_device *dev,
                                           struct cpuidle_driver *drv, int idx)
{
        u32 *state = __this_cpu_read(psci_cpuidle_data.psci_states);

        return CPU_PM_CPU_IDLE_ENTER_PARAM_RCU(psci_cpu_suspend_enter, idx, state[idx]);
}

static const struct of_device_id psci_idle_state_match[] = {
        { .compatible = "arm,idle-state",
          .data = psci_enter_idle_state },
        { },
};

int psci_dt_parse_state_node(struct device_node *np, u32 *state)
{
        int err = of_property_read_u32(np, "arm,psci-suspend-param", state);

        if (err) {
                pr_warn("%pOF missing arm,psci-suspend-param property\n", np);
                return err;
        }

        if (!psci_power_state_is_valid(*state)) {
                pr_warn("Invalid PSCI power state %#x\n", *state);
                return -EINVAL;
        }

        return 0;
}

static int psci_dt_cpu_init_topology(struct cpuidle_driver *drv,
                                     struct psci_cpuidle_data *data,
                                     unsigned int state_count, int cpu)
{
        /* Currently limit the hierarchical topology to be used in OSI mode. */
        if (!psci_has_osi_support())
                return 0;

        data->dev = dt_idle_attach_cpu(cpu, "psci");
        if (IS_ERR_OR_NULL(data->dev))
                return PTR_ERR_OR_ZERO(data->dev);

        psci_cpuidle_use_syscore = true;

        /*
         * Using the deepest state for the CPU to trigger a potential selection
         * of a shared state for the domain, assumes the domain states are all
         * deeper states. On PREEMPT_RT the hierarchical topology is limited to
         * s2ram and s2idle.
         */
        drv->states[state_count - 1].enter_s2idle = psci_enter_s2idle_domain_idle_state;
        if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                drv->states[state_count - 1].enter = psci_enter_domain_idle_state;

        return 0;
}

static int psci_dt_cpu_init_idle(struct device *dev, struct cpuidle_driver *drv,
                                 struct device_node *cpu_node,
                                 unsigned int state_count, int cpu)
{
        int i, ret = 0;
        u32 *psci_states;
        struct device_node *state_node;
        struct psci_cpuidle_data *data = per_cpu_ptr(&psci_cpuidle_data, cpu);

        state_count++; /* Add WFI state too */
        psci_states = devm_kcalloc(dev, state_count, sizeof(*psci_states),
                                   GFP_KERNEL);
        if (!psci_states)
                return -ENOMEM;

        for (i = 1; i < state_count; i++) {
                state_node = of_get_cpu_state_node(cpu_node, i - 1);
                if (!state_node)
                        break;

                ret = psci_dt_parse_state_node(state_node, &psci_states[i]);
                of_node_put(state_node);

                if (ret)
                        return ret;

                pr_debug("psci-power-state %#x index %d\n", psci_states[i], i);
        }

        if (i != state_count)
                return -ENODEV;

        /* Initialize optional data, used for the hierarchical topology. */
        ret = psci_dt_cpu_init_topology(drv, data, state_count, cpu);
        if (ret < 0)
                return ret;

        /* Idle states parsed correctly, store them in the per-cpu struct. */
        data->psci_states = psci_states;
        return 0;
}

static int psci_cpu_init_idle(struct device *dev, struct cpuidle_driver *drv,
                              unsigned int cpu, unsigned int state_count)
{
        struct device_node *cpu_node;
        int ret;

        /*
         * If the PSCI cpu_suspend function hook has not been initialized
         * idle states must not be enabled, so bail out
         */
        if (!psci_ops.cpu_suspend)
                return -EOPNOTSUPP;

        cpu_node = of_cpu_device_node_get(cpu);
        if (!cpu_node)
                return -ENODEV;

        ret = psci_dt_cpu_init_idle(dev, drv, cpu_node, state_count, cpu);

        of_node_put(cpu_node);

        return ret;
}

static void psci_cpu_deinit_idle(int cpu)
{
        struct psci_cpuidle_data *data = per_cpu_ptr(&psci_cpuidle_data, cpu);

        dt_idle_detach_cpu(data->dev);
        psci_cpuidle_use_syscore = false;
}

static int psci_idle_init_cpu(struct device *dev, int cpu)
{
        struct cpuidle_driver *drv;
        struct device_node *cpu_node;
        const char *enable_method;
        int ret = 0;

        cpu_node = of_cpu_device_node_get(cpu);
        if (!cpu_node)
                return -ENODEV;

        /*
         * Check whether the enable-method for the cpu is PSCI, fail
         * if it is not.
         */
        enable_method = of_get_property(cpu_node, "enable-method", NULL);
        if (!enable_method || (strcmp(enable_method, "psci")))
                ret = -ENODEV;

        of_node_put(cpu_node);
        if (ret)
                return ret;

        drv = devm_kzalloc(dev, sizeof(*drv), GFP_KERNEL);
        if (!drv)
                return -ENOMEM;

        drv->name = "psci_idle";
        drv->owner = THIS_MODULE;
        drv->cpumask = (struct cpumask *)cpumask_of(cpu);

        /*
         * PSCI idle states relies on architectural WFI to be represented as
         * state index 0.
         */
        drv->states[0].enter = psci_enter_idle_state;
        drv->states[0].exit_latency = 1;
        drv->states[0].target_residency = 1;
        drv->states[0].power_usage = UINT_MAX;
        strscpy(drv->states[0].name, "WFI");
        strscpy(drv->states[0].desc, "ARM WFI");

        /*
         * If no DT idle states are detected (ret == 0) let the driver
         * initialization fail accordingly since there is no reason to
         * initialize the idle driver if only wfi is supported, the
         * default archictectural back-end already executes wfi
         * on idle entry.
         */
        ret = dt_init_idle_driver(drv, psci_idle_state_match, 1);
        if (ret <= 0)
                return ret ? : -ENODEV;

        /*
         * Initialize PSCI idle states.
         */
        ret = psci_cpu_init_idle(dev, drv, cpu, ret);
        if (ret) {
                pr_err("CPU %d failed to PSCI idle\n", cpu);
                return ret;
        }

        ret = cpuidle_register(drv, NULL);
        if (ret)
                goto deinit;

        cpuidle_cooling_register(drv);

        return 0;
deinit:
        psci_cpu_deinit_idle(cpu);
        return ret;
}

/*
 * psci_idle_probe - Initializes PSCI cpuidle driver
 *
 * Initializes PSCI cpuidle driver for all present CPUs, if any CPU fails
 * to register cpuidle driver then rollback to cancel all CPUs
 * registration.
 */
static int psci_cpuidle_probe(struct faux_device *fdev)
{
        int cpu, ret;
        struct cpuidle_driver *drv;
        struct cpuidle_device *dev;

        for_each_present_cpu(cpu) {
                ret = psci_idle_init_cpu(&fdev->dev, cpu);
                if (ret)
                        goto out_fail;
        }

        psci_idle_init_syscore();
        psci_idle_init_cpuhp();
        return 0;

out_fail:
        while (--cpu >= 0) {
                dev = per_cpu(cpuidle_devices, cpu);
                drv = cpuidle_get_cpu_driver(dev);
                cpuidle_unregister(drv);
                psci_cpu_deinit_idle(cpu);
        }

        return ret;
}

static struct faux_device_ops psci_cpuidle_ops = {
        .probe = psci_cpuidle_probe,
};

static bool __init dt_idle_state_present(void)
{
        struct device_node *cpu_node __free(device_node) =
                        of_cpu_device_node_get(cpumask_first(cpu_possible_mask));
        if (!cpu_node)
                return false;

        struct device_node *state_node __free(device_node) =
                        of_get_cpu_state_node(cpu_node, 0);
        if (!state_node)
                return false;

        return !!of_match_node(psci_idle_state_match, state_node);
}

static int __init psci_idle_init(void)
{
        struct faux_device *fdev;

        if (!dt_idle_state_present())
                return 0;

        fdev = faux_device_create("psci-cpuidle", NULL, &psci_cpuidle_ops);
        if (!fdev) {
                pr_err("Failed to create psci-cpuidle device\n");
                return -ENODEV;
        }

        return 0;
}
device_initcall(psci_idle_init);