// SPDX-License-Identifier: GPL-2.0-only
/*
 * System Control and Power Interface (SCPI) based CPUFreq Interface driver
 *
 * Copyright (C) 2015 ARM Ltd.
 * Sudeep Holla <sudeep.holla@arm.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/clk.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/cpumask.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/scpi_protocol.h>
#include <linux/slab.h>
#include <linux/types.h>

struct scpi_data {
        struct clk *clk;
        struct device *cpu_dev;
};

static struct scpi_ops *scpi_ops;

static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
{
        struct cpufreq_policy *policy;
        struct scpi_data *priv;
        unsigned long rate;

        policy = cpufreq_cpu_get_raw(cpu);
        if (unlikely(!policy))
                return 0;

        priv = policy->driver_data;
        rate = clk_get_rate(priv->clk);

        return rate / 1000;
}

static int
scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
{
        unsigned long freq_khz = policy->freq_table[index].frequency;
        struct scpi_data *priv = policy->driver_data;
        unsigned long rate = freq_khz * 1000;
        int ret;

        ret = clk_set_rate(priv->clk, rate);

        if (ret)
                return ret;

        if (clk_get_rate(priv->clk) / 1000 != freq_khz)
                return -EIO;

        return 0;
}

static int
scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
{
        int cpu, domain, tdomain;
        struct device *tcpu_dev;

        domain = scpi_ops->device_domain_id(cpu_dev);
        if (domain < 0)
                return domain;

        for_each_present_cpu(cpu) {
                if (cpu == cpu_dev->id)
                        continue;

                tcpu_dev = get_cpu_device(cpu);
                if (!tcpu_dev)
                        continue;

                tdomain = scpi_ops->device_domain_id(tcpu_dev);
                if (tdomain == domain)
                        cpumask_set_cpu(cpu, cpumask);
        }

        return 0;
}

static int scpi_cpufreq_init(struct cpufreq_policy *policy)
{
        int ret;
        unsigned int latency;
        struct device *cpu_dev;
        struct scpi_data *priv;
        struct cpufreq_frequency_table *freq_table;

        cpu_dev = get_cpu_device(policy->cpu);
        if (!cpu_dev) {
                pr_err("failed to get cpu%d device\n", policy->cpu);
                return -ENODEV;
        }

        ret = scpi_ops->add_opps_to_device(cpu_dev);
        if (ret) {
                dev_warn(cpu_dev, "failed to add opps to the device\n");
                return ret;
        }

        ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
        if (ret) {
                dev_warn(cpu_dev, "failed to get sharing cpumask\n");
                return ret;
        }

        ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
        if (ret) {
                dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
                        __func__, ret);
                return ret;
        }

        ret = dev_pm_opp_get_opp_count(cpu_dev);
        if (ret <= 0) {
                dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
                ret = -EPROBE_DEFER;
                goto out_free_opp;
        }

        priv = kzalloc_obj(*priv);
        if (!priv) {
                ret = -ENOMEM;
                goto out_free_opp;
        }

        ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
        if (ret) {
                dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
                goto out_free_priv;
        }

        priv->cpu_dev = cpu_dev;
        priv->clk = clk_get(cpu_dev, NULL);
        if (IS_ERR(priv->clk)) {
                dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
                        __func__, cpu_dev->id);
                ret = PTR_ERR(priv->clk);
                goto out_free_cpufreq_table;
        }

        policy->driver_data = priv;
        policy->freq_table = freq_table;

        /* scpi allows DVFS request for any domain from any CPU */
        policy->dvfs_possible_from_any_cpu = true;

        latency = scpi_ops->get_transition_latency(cpu_dev);
        if (!latency)
                latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS;

        policy->cpuinfo.transition_latency = latency;

        policy->fast_switch_possible = false;

        return 0;

out_free_cpufreq_table:
        dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
out_free_priv:
        kfree(priv);
out_free_opp:
        dev_pm_opp_remove_all_dynamic(cpu_dev);

        return ret;
}

static void scpi_cpufreq_exit(struct cpufreq_policy *policy)
{
        struct scpi_data *priv = policy->driver_data;

        clk_put(priv->clk);
        dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
        dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
        kfree(priv);
}

static struct cpufreq_driver scpi_cpufreq_driver = {
        .name   = "scpi-cpufreq",
        .flags  = CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
                  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
                  CPUFREQ_IS_COOLING_DEV,
        .verify = cpufreq_generic_frequency_table_verify,
        .get    = scpi_cpufreq_get_rate,
        .init   = scpi_cpufreq_init,
        .exit   = scpi_cpufreq_exit,
        .target_index   = scpi_cpufreq_set_target,
        .register_em    = cpufreq_register_em_with_opp,
};

static int scpi_cpufreq_probe(struct platform_device *pdev)
{
        int ret;

        scpi_ops = get_scpi_ops();
        if (!scpi_ops)
                return -EIO;

        ret = cpufreq_register_driver(&scpi_cpufreq_driver);
        if (ret)
                dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
                        __func__, ret);
        return ret;
}

static void scpi_cpufreq_remove(struct platform_device *pdev)
{
        cpufreq_unregister_driver(&scpi_cpufreq_driver);
        scpi_ops = NULL;
}

static struct platform_driver scpi_cpufreq_platdrv = {
        .driver = {
                .name   = "scpi-cpufreq",
        },
        .probe          = scpi_cpufreq_probe,
        .remove         = scpi_cpufreq_remove,
};
module_platform_driver(scpi_cpufreq_platdrv);

MODULE_ALIAS("platform:scpi-cpufreq");
MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
MODULE_LICENSE("GPL v2");