// SPDX-License-Identifier: GPL-2.0
/*
 * Allwinner CPUFreq nvmem based driver
 *
 * The sun50i-cpufreq-nvmem driver reads the efuse value from the SoC to
 * provide the OPP framework with required information.
 *
 * Copyright (C) 2019 Yangtao Li <tiny.windzz@gmail.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/nvmem-consumer.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/slab.h>

#define MAX_NAME_LEN    7

#define NVMEM_MASK      0x7
#define NVMEM_SHIFT     5

static struct platform_device *cpufreq_dt_pdev, *sun50i_cpufreq_pdev;

/**
 * sun50i_cpufreq_get_efuse() - Determine speed grade from efuse value
 * @versions: Set to the value parsed from efuse
 *
 * Returns 0 if success.
 */
static int sun50i_cpufreq_get_efuse(u32 *versions)
{
        struct nvmem_cell *speedbin_nvmem;
        struct device_node *np;
        struct device *cpu_dev;
        u32 *speedbin, efuse_value;
        size_t len;
        int ret;

        cpu_dev = get_cpu_device(0);
        if (!cpu_dev)
                return -ENODEV;

        np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
        if (!np)
                return -ENOENT;

        ret = of_device_is_compatible(np,
                                      "allwinner,sun50i-h6-operating-points");
        if (!ret) {
                of_node_put(np);
                return -ENOENT;
        }

        speedbin_nvmem = of_nvmem_cell_get(np, NULL);
        of_node_put(np);
        if (IS_ERR(speedbin_nvmem)) {
                if (PTR_ERR(speedbin_nvmem) != -EPROBE_DEFER)
                        pr_err("Could not get nvmem cell: %ld\n",
                               PTR_ERR(speedbin_nvmem));
                return PTR_ERR(speedbin_nvmem);
        }

        speedbin = nvmem_cell_read(speedbin_nvmem, &len);
        nvmem_cell_put(speedbin_nvmem);
        if (IS_ERR(speedbin))
                return PTR_ERR(speedbin);

        efuse_value = (*speedbin >> NVMEM_SHIFT) & NVMEM_MASK;

        /*
         * We treat unexpected efuse values as if the SoC was from
         * the slowest bin. Expected efuse values are 1-3, slowest
         * to fastest.
         */
        if (efuse_value >= 1 && efuse_value <= 3)
                *versions = efuse_value - 1;
        else
                *versions = 0;

        kfree(speedbin);
        return 0;
};

static int sun50i_cpufreq_nvmem_probe(struct platform_device *pdev)
{
        struct opp_table **opp_tables;
        char name[MAX_NAME_LEN];
        unsigned int cpu;
        u32 speed = 0;
        int ret;

        opp_tables = kcalloc(num_possible_cpus(), sizeof(*opp_tables),
                             GFP_KERNEL);
        if (!opp_tables)
                return -ENOMEM;

        ret = sun50i_cpufreq_get_efuse(&speed);
        if (ret) {
                kfree(opp_tables);
                return ret;
        }

        snprintf(name, MAX_NAME_LEN, "speed%d", speed);

        for_each_possible_cpu(cpu) {
                struct device *cpu_dev = get_cpu_device(cpu);

                if (!cpu_dev) {
                        ret = -ENODEV;
                        goto free_opp;
                }

                opp_tables[cpu] = dev_pm_opp_set_prop_name(cpu_dev, name);
                if (IS_ERR(opp_tables[cpu])) {
                        ret = PTR_ERR(opp_tables[cpu]);
                        pr_err("Failed to set prop name\n");
                        goto free_opp;
                }
        }

        cpufreq_dt_pdev = platform_device_register_simple("cpufreq-dt", -1,
                                                          NULL, 0);
        if (!IS_ERR(cpufreq_dt_pdev)) {
                platform_set_drvdata(pdev, opp_tables);
                return 0;
        }

        ret = PTR_ERR(cpufreq_dt_pdev);
        pr_err("Failed to register platform device\n");

free_opp:
        for_each_possible_cpu(cpu) {
                if (IS_ERR_OR_NULL(opp_tables[cpu]))
                        break;
                dev_pm_opp_put_prop_name(opp_tables[cpu]);
        }
        kfree(opp_tables);

        return ret;
}

static int sun50i_cpufreq_nvmem_remove(struct platform_device *pdev)
{
        struct opp_table **opp_tables = platform_get_drvdata(pdev);
        unsigned int cpu;

        platform_device_unregister(cpufreq_dt_pdev);

        for_each_possible_cpu(cpu)
                dev_pm_opp_put_prop_name(opp_tables[cpu]);

        kfree(opp_tables);

        return 0;
}

static struct platform_driver sun50i_cpufreq_driver = {
        .probe = sun50i_cpufreq_nvmem_probe,
        .remove = sun50i_cpufreq_nvmem_remove,
        .driver = {
                .name = "sun50i-cpufreq-nvmem",
        },
};

static const struct of_device_id sun50i_cpufreq_match_list[] = {
        { .compatible = "allwinner,sun50i-h6" },
        {}
};
MODULE_DEVICE_TABLE(of, sun50i_cpufreq_match_list);

static const struct of_device_id *sun50i_cpufreq_match_node(void)
{
        const struct of_device_id *match;
        struct device_node *np;

        np = of_find_node_by_path("/");
        match = of_match_node(sun50i_cpufreq_match_list, np);
        of_node_put(np);

        return match;
}

/*
 * Since the driver depends on nvmem drivers, which may return EPROBE_DEFER,
 * all the real activity is done in the probe, which may be defered as well.
 * The init here is only registering the driver and the platform device.
 */
static int __init sun50i_cpufreq_init(void)
{
        const struct of_device_id *match;
        int ret;

        match = sun50i_cpufreq_match_node();
        if (!match)
                return -ENODEV;

        ret = platform_driver_register(&sun50i_cpufreq_driver);
        if (unlikely(ret < 0))
                return ret;

        sun50i_cpufreq_pdev =
                platform_device_register_simple("sun50i-cpufreq-nvmem",
                                                -1, NULL, 0);
        ret = PTR_ERR_OR_ZERO(sun50i_cpufreq_pdev);
        if (ret == 0)
                return 0;

        platform_driver_unregister(&sun50i_cpufreq_driver);
        return ret;
}
module_init(sun50i_cpufreq_init);

static void __exit sun50i_cpufreq_exit(void)
{
        platform_device_unregister(sun50i_cpufreq_pdev);
        platform_driver_unregister(&sun50i_cpufreq_driver);
}
module_exit(sun50i_cpufreq_exit);

MODULE_DESCRIPTION("Sun50i-h6 cpufreq driver");
MODULE_LICENSE("GPL v2");