/*
 * Copyright (C) 2010 Google, Inc.
 *
 * Author:
 *      Colin Cross <ccross@google.com>
 *      Based on arch/arm/plat-omap/cpu-omap.c, (C) 2005 Nokia Corporation
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/types.h>

static struct cpufreq_frequency_table freq_table[] = {
        { .frequency = 216000 },
        { .frequency = 312000 },
        { .frequency = 456000 },
        { .frequency = 608000 },
        { .frequency = 760000 },
        { .frequency = 816000 },
        { .frequency = 912000 },
        { .frequency = 1000000 },
        { .frequency = CPUFREQ_TABLE_END },
};

struct tegra20_cpufreq {
        struct device *dev;
        struct cpufreq_driver driver;
        struct clk *cpu_clk;
        struct clk *pll_x_clk;
        struct clk *pll_p_clk;
        bool pll_x_prepared;
};

static unsigned int tegra_get_intermediate(struct cpufreq_policy *policy,
                                           unsigned int index)
{
        struct tegra20_cpufreq *cpufreq = cpufreq_get_driver_data();
        unsigned int ifreq = clk_get_rate(cpufreq->pll_p_clk) / 1000;

        /*
         * Don't switch to intermediate freq if:
         * - we are already at it, i.e. policy->cur == ifreq
         * - index corresponds to ifreq
         */
        if (freq_table[index].frequency == ifreq || policy->cur == ifreq)
                return 0;

        return ifreq;
}

static int tegra_target_intermediate(struct cpufreq_policy *policy,
                                     unsigned int index)
{
        struct tegra20_cpufreq *cpufreq = cpufreq_get_driver_data();
        int ret;

        /*
         * Take an extra reference to the main pll so it doesn't turn
         * off when we move the cpu off of it as enabling it again while we
         * switch to it from tegra_target() would take additional time.
         *
         * When target-freq is equal to intermediate freq we don't need to
         * switch to an intermediate freq and so this routine isn't called.
         * Also, we wouldn't be using pll_x anymore and must not take extra
         * reference to it, as it can be disabled now to save some power.
         */
        clk_prepare_enable(cpufreq->pll_x_clk);

        ret = clk_set_parent(cpufreq->cpu_clk, cpufreq->pll_p_clk);
        if (ret)
                clk_disable_unprepare(cpufreq->pll_x_clk);
        else
                cpufreq->pll_x_prepared = true;

        return ret;
}

static int tegra_target(struct cpufreq_policy *policy, unsigned int index)
{
        struct tegra20_cpufreq *cpufreq = cpufreq_get_driver_data();
        unsigned long rate = freq_table[index].frequency;
        unsigned int ifreq = clk_get_rate(cpufreq->pll_p_clk) / 1000;
        int ret;

        /*
         * target freq == pll_p, don't need to take extra reference to pll_x_clk
         * as it isn't used anymore.
         */
        if (rate == ifreq)
                return clk_set_parent(cpufreq->cpu_clk, cpufreq->pll_p_clk);

        ret = clk_set_rate(cpufreq->pll_x_clk, rate * 1000);
        /* Restore to earlier frequency on error, i.e. pll_x */
        if (ret)
                dev_err(cpufreq->dev, "Failed to change pll_x to %lu\n", rate);

        ret = clk_set_parent(cpufreq->cpu_clk, cpufreq->pll_x_clk);
        /* This shouldn't fail while changing or restoring */
        WARN_ON(ret);

        /*
         * Drop count to pll_x clock only if we switched to intermediate freq
         * earlier while transitioning to a target frequency.
         */
        if (cpufreq->pll_x_prepared) {
                clk_disable_unprepare(cpufreq->pll_x_clk);
                cpufreq->pll_x_prepared = false;
        }

        return ret;
}

static int tegra_cpu_init(struct cpufreq_policy *policy)
{
        struct tegra20_cpufreq *cpufreq = cpufreq_get_driver_data();
        int ret;

        clk_prepare_enable(cpufreq->cpu_clk);

        /* FIXME: what's the actual transition time? */
        ret = cpufreq_generic_init(policy, freq_table, 300 * 1000);
        if (ret) {
                clk_disable_unprepare(cpufreq->cpu_clk);
                return ret;
        }

        policy->clk = cpufreq->cpu_clk;
        policy->suspend_freq = freq_table[0].frequency;
        return 0;
}

static int tegra_cpu_exit(struct cpufreq_policy *policy)
{
        struct tegra20_cpufreq *cpufreq = cpufreq_get_driver_data();

        clk_disable_unprepare(cpufreq->cpu_clk);
        return 0;
}

static int tegra20_cpufreq_probe(struct platform_device *pdev)
{
        struct tegra20_cpufreq *cpufreq;
        int err;

        cpufreq = devm_kzalloc(&pdev->dev, sizeof(*cpufreq), GFP_KERNEL);
        if (!cpufreq)
                return -ENOMEM;

        cpufreq->cpu_clk = clk_get_sys(NULL, "cclk");
        if (IS_ERR(cpufreq->cpu_clk))
                return PTR_ERR(cpufreq->cpu_clk);

        cpufreq->pll_x_clk = clk_get_sys(NULL, "pll_x");
        if (IS_ERR(cpufreq->pll_x_clk)) {
                err = PTR_ERR(cpufreq->pll_x_clk);
                goto put_cpu;
        }

        cpufreq->pll_p_clk = clk_get_sys(NULL, "pll_p");
        if (IS_ERR(cpufreq->pll_p_clk)) {
                err = PTR_ERR(cpufreq->pll_p_clk);
                goto put_pll_x;
        }

        cpufreq->dev = &pdev->dev;
        cpufreq->driver.get = cpufreq_generic_get;
        cpufreq->driver.attr = cpufreq_generic_attr;
        cpufreq->driver.init = tegra_cpu_init;
        cpufreq->driver.exit = tegra_cpu_exit;
        cpufreq->driver.flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK;
        cpufreq->driver.verify = cpufreq_generic_frequency_table_verify;
        cpufreq->driver.suspend = cpufreq_generic_suspend;
        cpufreq->driver.driver_data = cpufreq;
        cpufreq->driver.target_index = tegra_target;
        cpufreq->driver.get_intermediate = tegra_get_intermediate;
        cpufreq->driver.target_intermediate = tegra_target_intermediate;
        snprintf(cpufreq->driver.name, CPUFREQ_NAME_LEN, "tegra");

        err = cpufreq_register_driver(&cpufreq->driver);
        if (err)
                goto put_pll_p;

        platform_set_drvdata(pdev, cpufreq);

        return 0;

put_pll_p:
        clk_put(cpufreq->pll_p_clk);
put_pll_x:
        clk_put(cpufreq->pll_x_clk);
put_cpu:
        clk_put(cpufreq->cpu_clk);

        return err;
}

static int tegra20_cpufreq_remove(struct platform_device *pdev)
{
        struct tegra20_cpufreq *cpufreq = platform_get_drvdata(pdev);

        cpufreq_unregister_driver(&cpufreq->driver);

        clk_put(cpufreq->pll_p_clk);
        clk_put(cpufreq->pll_x_clk);
        clk_put(cpufreq->cpu_clk);

        return 0;
}

static struct platform_driver tegra20_cpufreq_driver = {
        .probe          = tegra20_cpufreq_probe,
        .remove         = tegra20_cpufreq_remove,
        .driver         = {
                .name   = "tegra20-cpufreq",
        },
};
module_platform_driver(tegra20_cpufreq_driver);

MODULE_ALIAS("platform:tegra20-cpufreq");
MODULE_AUTHOR("Colin Cross <ccross@android.com>");
MODULE_DESCRIPTION("NVIDIA Tegra20 cpufreq driver");
MODULE_LICENSE("GPL");