/*
 *      kirkwood_freq.c: cpufreq driver for the Marvell kirkwood
 *
 *      Copyright (C) 2013 Andrew Lunn <andrew@lunn.ch>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/cpufreq.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <asm/proc-fns.h>

#define CPU_SW_INT_BLK BIT(28)

static struct priv
{
        struct clk *cpu_clk;
        struct clk *ddr_clk;
        struct clk *powersave_clk;
        struct device *dev;
        void __iomem *base;
} priv;

#define STATE_CPU_FREQ 0x01
#define STATE_DDR_FREQ 0x02

/*
 * Kirkwood can swap the clock to the CPU between two clocks:
 *
 * - cpu clk
 * - ddr clk
 *
 * The frequencies are set at runtime before registering this *
 * table.
 */
static struct cpufreq_frequency_table kirkwood_freq_table[] = {
        {STATE_CPU_FREQ,        0}, /* CPU uses cpuclk */
        {STATE_DDR_FREQ,        0}, /* CPU uses ddrclk */
        {0,                     CPUFREQ_TABLE_END},
};

static unsigned int kirkwood_cpufreq_get_cpu_frequency(unsigned int cpu)
{
        if (__clk_is_enabled(priv.powersave_clk))
                return kirkwood_freq_table[1].frequency;
        return kirkwood_freq_table[0].frequency;
}

static void kirkwood_cpufreq_set_cpu_state(struct cpufreq_policy *policy,
                unsigned int index)
{
        struct cpufreq_freqs freqs;
        unsigned int state = kirkwood_freq_table[index].driver_data;
        unsigned long reg;

        freqs.old = kirkwood_cpufreq_get_cpu_frequency(0);
        freqs.new = kirkwood_freq_table[index].frequency;

        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);

        dev_dbg(priv.dev, "Attempting to set frequency to %i KHz\n",
                kirkwood_freq_table[index].frequency);
        dev_dbg(priv.dev, "old frequency was %i KHz\n",
                kirkwood_cpufreq_get_cpu_frequency(0));

        if (freqs.old != freqs.new) {
                local_irq_disable();

                /* Disable interrupts to the CPU */
                reg = readl_relaxed(priv.base);
                reg |= CPU_SW_INT_BLK;
                writel_relaxed(reg, priv.base);

                switch (state) {
                case STATE_CPU_FREQ:
                        clk_disable(priv.powersave_clk);
                        break;
                case STATE_DDR_FREQ:
                        clk_enable(priv.powersave_clk);
                        break;
                }

                /* Wait-for-Interrupt, while the hardware changes frequency */
                cpu_do_idle();

                /* Enable interrupts to the CPU */
                reg = readl_relaxed(priv.base);
                reg &= ~CPU_SW_INT_BLK;
                writel_relaxed(reg, priv.base);

                local_irq_enable();
        }
        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
};

static int kirkwood_cpufreq_verify(struct cpufreq_policy *policy)
{
        return cpufreq_frequency_table_verify(policy, kirkwood_freq_table);
}

static int kirkwood_cpufreq_target(struct cpufreq_policy *policy,
                            unsigned int target_freq,
                            unsigned int relation)
{
        unsigned int index = 0;

        if (cpufreq_frequency_table_target(policy, kirkwood_freq_table,
                                target_freq, relation, &index))
                return -EINVAL;

        kirkwood_cpufreq_set_cpu_state(policy, index);

        return 0;
}

/* Module init and exit code */
static int kirkwood_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
        int result;

        /* cpuinfo and default policy values */
        policy->cpuinfo.transition_latency = 5000; /* 5uS */
        policy->cur = kirkwood_cpufreq_get_cpu_frequency(0);

        result = cpufreq_frequency_table_cpuinfo(policy, kirkwood_freq_table);
        if (result)
                return result;

        cpufreq_frequency_table_get_attr(kirkwood_freq_table, policy->cpu);

        return 0;
}

static int kirkwood_cpufreq_cpu_exit(struct cpufreq_policy *policy)
{
        cpufreq_frequency_table_put_attr(policy->cpu);
        return 0;
}

static struct freq_attr *kirkwood_cpufreq_attr[] = {
        &cpufreq_freq_attr_scaling_available_freqs,
        NULL,
};

static struct cpufreq_driver kirkwood_cpufreq_driver = {
        .get    = kirkwood_cpufreq_get_cpu_frequency,
        .verify = kirkwood_cpufreq_verify,
        .target = kirkwood_cpufreq_target,
        .init   = kirkwood_cpufreq_cpu_init,
        .exit   = kirkwood_cpufreq_cpu_exit,
        .name   = "kirkwood-cpufreq",
        .attr   = kirkwood_cpufreq_attr,
};

static int kirkwood_cpufreq_probe(struct platform_device *pdev)
{
        struct device_node *np;
        struct resource *res;
        int err;

        priv.dev = &pdev->dev;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        priv.base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(priv.base))
                return PTR_ERR(priv.base);

        np = of_cpu_device_node_get(0);
        if (!np) {
                dev_err(&pdev->dev, "failed to get cpu device node\n");
                return -ENODEV;
        }

        priv.cpu_clk = of_clk_get_by_name(np, "cpu_clk");
        if (IS_ERR(priv.cpu_clk)) {
                dev_err(priv.dev, "Unable to get cpuclk");
                return PTR_ERR(priv.cpu_clk);
        }

        clk_prepare_enable(priv.cpu_clk);
        kirkwood_freq_table[0].frequency = clk_get_rate(priv.cpu_clk) / 1000;

        priv.ddr_clk = of_clk_get_by_name(np, "ddrclk");
        if (IS_ERR(priv.ddr_clk)) {
                dev_err(priv.dev, "Unable to get ddrclk");
                err = PTR_ERR(priv.ddr_clk);
                goto out_cpu;
        }

        clk_prepare_enable(priv.ddr_clk);
        kirkwood_freq_table[1].frequency = clk_get_rate(priv.ddr_clk) / 1000;

        priv.powersave_clk = of_clk_get_by_name(np, "powersave");
        if (IS_ERR(priv.powersave_clk)) {
                dev_err(priv.dev, "Unable to get powersave");
                err = PTR_ERR(priv.powersave_clk);
                goto out_ddr;
        }
        clk_prepare(priv.powersave_clk);

        of_node_put(np);
        np = NULL;

        err = cpufreq_register_driver(&kirkwood_cpufreq_driver);
        if (!err)
                return 0;

        dev_err(priv.dev, "Failed to register cpufreq driver");

        clk_disable_unprepare(priv.powersave_clk);
out_ddr:
        clk_disable_unprepare(priv.ddr_clk);
out_cpu:
        clk_disable_unprepare(priv.cpu_clk);
        of_node_put(np);

        return err;
}

static int kirkwood_cpufreq_remove(struct platform_device *pdev)
{
        cpufreq_unregister_driver(&kirkwood_cpufreq_driver);

        clk_disable_unprepare(priv.powersave_clk);
        clk_disable_unprepare(priv.ddr_clk);
        clk_disable_unprepare(priv.cpu_clk);

        return 0;
}

static struct platform_driver kirkwood_cpufreq_platform_driver = {
        .probe = kirkwood_cpufreq_probe,
        .remove = kirkwood_cpufreq_remove,
        .driver = {
                .name = "kirkwood-cpufreq",
                .owner = THIS_MODULE,
        },
};

module_platform_driver(kirkwood_cpufreq_platform_driver);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Andrew Lunn <andrew@lunn.ch");
MODULE_DESCRIPTION("cpufreq driver for Marvell's kirkwood CPU");
MODULE_ALIAS("platform:kirkwood-cpufreq");