/*
 * Copyright (C) 2013 - 2014 Texas Instruments Incorporated - http://www.ti.com
 *
 * Authors:
 *    Jyri Sarha <jsarha@ti.com>
 *    Sergej Sawazki <ce3a@gmx.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Gpio controlled clock implementation
 */

#include <linux/clk-provider.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/of_gpio.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/of_device.h>

/**
 * DOC: basic gpio gated clock which can be enabled and disabled
 *      with gpio output
 * Traits of this clock:
 * prepare - clk_(un)prepare only ensures parent is (un)prepared
 * enable - clk_enable and clk_disable are functional & control gpio
 * rate - inherits rate from parent.  No clk_set_rate support
 * parent - fixed parent.  No clk_set_parent support
 */

static int clk_gpio_gate_enable(struct clk_hw *hw)
{
        struct clk_gpio *clk = to_clk_gpio(hw);

        gpiod_set_value(clk->gpiod, 1);

        return 0;
}

static void clk_gpio_gate_disable(struct clk_hw *hw)
{
        struct clk_gpio *clk = to_clk_gpio(hw);

        gpiod_set_value(clk->gpiod, 0);
}

static int clk_gpio_gate_is_enabled(struct clk_hw *hw)
{
        struct clk_gpio *clk = to_clk_gpio(hw);

        return gpiod_get_value(clk->gpiod);
}

const struct clk_ops clk_gpio_gate_ops = {
        .enable = clk_gpio_gate_enable,
        .disable = clk_gpio_gate_disable,
        .is_enabled = clk_gpio_gate_is_enabled,
};
EXPORT_SYMBOL_GPL(clk_gpio_gate_ops);

/**
 * DOC: basic clock multiplexer which can be controlled with a gpio output
 * Traits of this clock:
 * prepare - clk_prepare only ensures that parents are prepared
 * rate - rate is only affected by parent switching.  No clk_set_rate support
 * parent - parent is adjustable through clk_set_parent
 */

static u8 clk_gpio_mux_get_parent(struct clk_hw *hw)
{
        struct clk_gpio *clk = to_clk_gpio(hw);

        return gpiod_get_value(clk->gpiod);
}

static int clk_gpio_mux_set_parent(struct clk_hw *hw, u8 index)
{
        struct clk_gpio *clk = to_clk_gpio(hw);

        gpiod_set_value(clk->gpiod, index);

        return 0;
}

const struct clk_ops clk_gpio_mux_ops = {
        .get_parent = clk_gpio_mux_get_parent,
        .set_parent = clk_gpio_mux_set_parent,
        .determine_rate = __clk_mux_determine_rate,
};
EXPORT_SYMBOL_GPL(clk_gpio_mux_ops);

static struct clk_hw *clk_register_gpio(struct device *dev, const char *name,
                const char * const *parent_names, u8 num_parents, unsigned gpio,
                bool active_low, unsigned long flags,
                const struct clk_ops *clk_gpio_ops)
{
        struct clk_gpio *clk_gpio;
        struct clk_hw *hw;
        struct clk_init_data init = {};
        unsigned long gpio_flags;
        int err;

        if (dev)
                clk_gpio = devm_kzalloc(dev, sizeof(*clk_gpio), GFP_KERNEL);
        else
                clk_gpio = kzalloc(sizeof(*clk_gpio), GFP_KERNEL);

        if (!clk_gpio)
                return ERR_PTR(-ENOMEM);

        if (active_low)
                gpio_flags = GPIOF_ACTIVE_LOW | GPIOF_OUT_INIT_HIGH;
        else
                gpio_flags = GPIOF_OUT_INIT_LOW;

        if (dev)
                err = devm_gpio_request_one(dev, gpio, gpio_flags, name);
        else
                err = gpio_request_one(gpio, gpio_flags, name);
        if (err) {
                if (err != -EPROBE_DEFER)
                        pr_err("%s: %s: Error requesting clock control gpio %u\n",
                                        __func__, name, gpio);
                if (!dev)
                        kfree(clk_gpio);

                return ERR_PTR(err);
        }

        init.name = name;
        init.ops = clk_gpio_ops;
        init.flags = flags | CLK_IS_BASIC;
        init.parent_names = parent_names;
        init.num_parents = num_parents;

        clk_gpio->gpiod = gpio_to_desc(gpio);
        clk_gpio->hw.init = &init;

        hw = &clk_gpio->hw;
        if (dev)
                err = devm_clk_hw_register(dev, hw);
        else
                err = clk_hw_register(NULL, hw);

        if (!err)
                return hw;

        if (!dev) {
                gpiod_put(clk_gpio->gpiod);
                kfree(clk_gpio);
        }

        return ERR_PTR(err);
}

/**
 * clk_hw_register_gpio_gate - register a gpio clock gate with the clock
 * framework
 * @dev: device that is registering this clock
 * @name: name of this clock
 * @parent_name: name of this clock's parent
 * @gpio: gpio number to gate this clock
 * @active_low: true if gpio should be set to 0 to enable clock
 * @flags: clock flags
 */
struct clk_hw *clk_hw_register_gpio_gate(struct device *dev, const char *name,
                const char *parent_name, unsigned gpio, bool active_low,
                unsigned long flags)
{
        return clk_register_gpio(dev, name,
                        (parent_name ? &parent_name : NULL),
                        (parent_name ? 1 : 0), gpio, active_low, flags,
                        &clk_gpio_gate_ops);
}
EXPORT_SYMBOL_GPL(clk_hw_register_gpio_gate);

struct clk *clk_register_gpio_gate(struct device *dev, const char *name,
                const char *parent_name, unsigned gpio, bool active_low,
                unsigned long flags)
{
        struct clk_hw *hw;

        hw = clk_hw_register_gpio_gate(dev, name, parent_name, gpio, active_low,
                                       flags);
        if (IS_ERR(hw))
                return ERR_CAST(hw);
        return hw->clk;
}
EXPORT_SYMBOL_GPL(clk_register_gpio_gate);

/**
 * clk_hw_register_gpio_mux - register a gpio clock mux with the clock framework
 * @dev: device that is registering this clock
 * @name: name of this clock
 * @parent_names: names of this clock's parents
 * @num_parents: number of parents listed in @parent_names
 * @gpio: gpio number to gate this clock
 * @active_low: true if gpio should be set to 0 to enable clock
 * @flags: clock flags
 */
struct clk_hw *clk_hw_register_gpio_mux(struct device *dev, const char *name,
                const char * const *parent_names, u8 num_parents, unsigned gpio,
                bool active_low, unsigned long flags)
{
        if (num_parents != 2) {
                pr_err("mux-clock %s must have 2 parents\n", name);
                return ERR_PTR(-EINVAL);
        }

        return clk_register_gpio(dev, name, parent_names, num_parents,
                        gpio, active_low, flags, &clk_gpio_mux_ops);
}
EXPORT_SYMBOL_GPL(clk_hw_register_gpio_mux);

struct clk *clk_register_gpio_mux(struct device *dev, const char *name,
                const char * const *parent_names, u8 num_parents, unsigned gpio,
                bool active_low, unsigned long flags)
{
        struct clk_hw *hw;

        hw = clk_hw_register_gpio_mux(dev, name, parent_names, num_parents,
                        gpio, active_low, flags);
        if (IS_ERR(hw))
                return ERR_CAST(hw);
        return hw->clk;
}
EXPORT_SYMBOL_GPL(clk_register_gpio_mux);

static int gpio_clk_driver_probe(struct platform_device *pdev)
{
        struct device_node *node = pdev->dev.of_node;
        const char **parent_names, *gpio_name;
        unsigned int num_parents;
        int gpio;
        enum of_gpio_flags of_flags;
        struct clk *clk;
        bool active_low, is_mux;

        num_parents = of_clk_get_parent_count(node);
        if (num_parents) {
                parent_names = devm_kcalloc(&pdev->dev, num_parents,
                                            sizeof(char *), GFP_KERNEL);
                if (!parent_names)
                        return -ENOMEM;

                of_clk_parent_fill(node, parent_names, num_parents);
        } else {
                parent_names = NULL;
        }

        is_mux = of_device_is_compatible(node, "gpio-mux-clock");

        gpio_name = is_mux ? "select-gpios" : "enable-gpios";
        gpio = of_get_named_gpio_flags(node, gpio_name, 0, &of_flags);
        if (gpio < 0) {
                if (gpio == -EPROBE_DEFER)
                        pr_debug("%s: %s: GPIOs not yet available, retry later\n",
                                        node->name, __func__);
                else
                        pr_err("%s: %s: Can't get '%s' DT property\n",
                                        node->name, __func__,
                                        gpio_name);
                return gpio;
        }

        active_low = of_flags & OF_GPIO_ACTIVE_LOW;

        if (is_mux)
                clk = clk_register_gpio_mux(&pdev->dev, node->name,
                                parent_names, num_parents, gpio, active_low, 0);
        else
                clk = clk_register_gpio_gate(&pdev->dev, node->name,
                                parent_names ?  parent_names[0] : NULL, gpio,
                                active_low, 0);
        if (IS_ERR(clk))
                return PTR_ERR(clk);

        return of_clk_add_provider(node, of_clk_src_simple_get, clk);
}

static const struct of_device_id gpio_clk_match_table[] = {
        { .compatible = "gpio-mux-clock" },
        { .compatible = "gpio-gate-clock" },
        { }
};

static struct platform_driver gpio_clk_driver = {
        .probe          = gpio_clk_driver_probe,
        .driver         = {
                .name   = "gpio-clk",
                .of_match_table = gpio_clk_match_table,
        },
};
builtin_platform_driver(gpio_clk_driver);