// SPDX-License-Identifier: GPL-2.0
/*
 * System Control and Power Interface (SCMI) based CPUFreq Interface driver
 *
 * Copyright (C) 2018-2021 ARM Ltd.
 * Sudeep Holla <sudeep.holla@arm.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/clk-provider.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/cpumask.h>
#include <linux/energy_model.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/pm_opp.h>
#include <linux/slab.h>
#include <linux/scmi_protocol.h>
#include <linux/types.h>

struct scmi_data {
        int domain_id;
        int nr_opp;
        struct device *cpu_dev;
        cpumask_var_t opp_shared_cpus;
};

static struct scmi_protocol_handle *ph;
static const struct scmi_perf_proto_ops *perf_ops;

static unsigned int scmi_cpufreq_get_rate(unsigned int cpu)
{
        struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
        struct scmi_data *priv = policy->driver_data;
        unsigned long rate;
        int ret;

        ret = perf_ops->freq_get(ph, priv->domain_id, &rate, false);
        if (ret)
                return 0;
        return rate / 1000;
}

/*
 * perf_ops->freq_set is not a synchronous, the actual OPP change will
 * happen asynchronously and can get notified if the events are
 * subscribed for by the SCMI firmware
 */
static int
scmi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
{
        struct scmi_data *priv = policy->driver_data;
        u64 freq = policy->freq_table[index].frequency;

        return perf_ops->freq_set(ph, priv->domain_id, freq * 1000, false);
}

static unsigned int scmi_cpufreq_fast_switch(struct cpufreq_policy *policy,
                                             unsigned int target_freq)
{
        struct scmi_data *priv = policy->driver_data;

        if (!perf_ops->freq_set(ph, priv->domain_id,
                                target_freq * 1000, true))
                return target_freq;

        return 0;
}

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

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

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

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

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

        return 0;
}

static int __maybe_unused
scmi_get_cpu_power(unsigned long *power, unsigned long *KHz,
                   struct device *cpu_dev)
{
        unsigned long Hz;
        int ret, domain;

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

        /* Get the power cost of the performance domain. */
        Hz = *KHz * 1000;
        ret = perf_ops->est_power_get(ph, domain, &Hz, power);
        if (ret)
                return ret;

        /* The EM framework specifies the frequency in KHz. */
        *KHz = Hz / 1000;

        return 0;
}

static int scmi_cpufreq_init(struct cpufreq_policy *policy)
{
        int ret, nr_opp;
        unsigned int latency;
        struct device *cpu_dev;
        struct scmi_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;
        }

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        if (!zalloc_cpumask_var(&priv->opp_shared_cpus, GFP_KERNEL)) {
                ret = -ENOMEM;
                goto out_free_priv;
        }

        /* Obtain CPUs that share SCMI performance controls */
        ret = scmi_get_sharing_cpus(cpu_dev, policy->cpus);
        if (ret) {
                dev_warn(cpu_dev, "failed to get sharing cpumask\n");
                goto out_free_cpumask;
        }

        /*
         * Obtain CPUs that share performance levels.
         * The OPP 'sharing cpus' info may come from DT through an empty opp
         * table and opp-shared.
         */
        ret = dev_pm_opp_of_get_sharing_cpus(cpu_dev, priv->opp_shared_cpus);
        if (ret || !cpumask_weight(priv->opp_shared_cpus)) {
                /*
                 * Either opp-table is not set or no opp-shared was found.
                 * Use the CPU mask from SCMI to designate CPUs sharing an OPP
                 * table.
                 */
                cpumask_copy(priv->opp_shared_cpus, policy->cpus);
        }

         /*
          * A previous CPU may have marked OPPs as shared for a few CPUs, based on
          * what OPP core provided. If the current CPU is part of those few, then
          * there is no need to add OPPs again.
          */
        nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
        if (nr_opp <= 0) {
                ret = perf_ops->device_opps_add(ph, cpu_dev);
                if (ret) {
                        dev_warn(cpu_dev, "failed to add opps to the device\n");
                        goto out_free_cpumask;
                }

                nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
                if (nr_opp <= 0) {
                        dev_err(cpu_dev, "%s: No OPPs for this device: %d\n",
                                __func__, nr_opp);

                        ret = -ENODEV;
                        goto out_free_opp;
                }

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

                        goto out_free_opp;
                }

                priv->nr_opp = nr_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_opp;
        }

        priv->cpu_dev = cpu_dev;
        priv->domain_id = perf_ops->device_domain_id(cpu_dev);

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

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

        latency = perf_ops->transition_latency_get(ph, cpu_dev);
        if (!latency)
                latency = CPUFREQ_ETERNAL;

        policy->cpuinfo.transition_latency = latency;

        policy->fast_switch_possible =
                perf_ops->fast_switch_possible(ph, cpu_dev);

        return 0;

out_free_opp:
        dev_pm_opp_remove_all_dynamic(cpu_dev);

out_free_cpumask:
        free_cpumask_var(priv->opp_shared_cpus);

out_free_priv:
        kfree(priv);

        return ret;
}

static int scmi_cpufreq_exit(struct cpufreq_policy *policy)
{
        struct scmi_data *priv = policy->driver_data;

        dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
        dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
        free_cpumask_var(priv->opp_shared_cpus);
        kfree(priv);

        return 0;
}

static void scmi_cpufreq_register_em(struct cpufreq_policy *policy)
{
        struct em_data_callback em_cb = EM_DATA_CB(scmi_get_cpu_power);
        bool power_scale_mw = perf_ops->power_scale_mw_get(ph);
        struct scmi_data *priv = policy->driver_data;

        /*
         * This callback will be called for each policy, but we don't need to
         * register with EM every time. Despite not being part of the same
         * policy, some CPUs may still share their perf-domains, and a CPU from
         * another policy may already have registered with EM on behalf of CPUs
         * of this policy.
         */
        if (!priv->nr_opp)
                return;

        em_dev_register_perf_domain(get_cpu_device(policy->cpu), priv->nr_opp,
                                    &em_cb, priv->opp_shared_cpus,
                                    power_scale_mw);
}

static struct cpufreq_driver scmi_cpufreq_driver = {
        .name   = "scmi",
        .flags  = CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
                  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
                  CPUFREQ_IS_COOLING_DEV,
        .verify = cpufreq_generic_frequency_table_verify,
        .attr   = cpufreq_generic_attr,
        .target_index   = scmi_cpufreq_set_target,
        .fast_switch    = scmi_cpufreq_fast_switch,
        .get    = scmi_cpufreq_get_rate,
        .init   = scmi_cpufreq_init,
        .exit   = scmi_cpufreq_exit,
        .register_em    = scmi_cpufreq_register_em,
};

static int scmi_cpufreq_probe(struct scmi_device *sdev)
{
        int ret;
        struct device *dev = &sdev->dev;
        const struct scmi_handle *handle;

        handle = sdev->handle;

        if (!handle)
                return -ENODEV;

        perf_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_PERF, &ph);
        if (IS_ERR(perf_ops))
                return PTR_ERR(perf_ops);

#ifdef CONFIG_COMMON_CLK
        /* dummy clock provider as needed by OPP if clocks property is used */
        if (of_find_property(dev->of_node, "#clock-cells", NULL))
                devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, NULL);
#endif

        ret = cpufreq_register_driver(&scmi_cpufreq_driver);
        if (ret) {
                dev_err(dev, "%s: registering cpufreq failed, err: %d\n",
                        __func__, ret);
        }

        return ret;
}

static void scmi_cpufreq_remove(struct scmi_device *sdev)
{
        cpufreq_unregister_driver(&scmi_cpufreq_driver);
}

static const struct scmi_device_id scmi_id_table[] = {
        { SCMI_PROTOCOL_PERF, "cpufreq" },
        { },
};
MODULE_DEVICE_TABLE(scmi, scmi_id_table);

static struct scmi_driver scmi_cpufreq_drv = {
        .name           = "scmi-cpufreq",
        .probe          = scmi_cpufreq_probe,
        .remove         = scmi_cpufreq_remove,
        .id_table       = scmi_id_table,
};
module_scmi_driver(scmi_cpufreq_drv);

MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
MODULE_DESCRIPTION("ARM SCMI CPUFreq interface driver");
MODULE_LICENSE("GPL v2");