/*
 * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
 * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
 * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
 *
 * 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.
 *
 * Adjustable divider clock implementation
 */

#include <linux/clk-provider.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/log2.h>

/*
 * DOC: basic adjustable divider clock that cannot gate
 *
 * Traits of this clock:
 * prepare - clk_prepare only ensures that parents are prepared
 * enable - clk_enable only ensures that parents are enabled
 * rate - rate is adjustable.  clk->rate = parent->rate / divisor
 * parent - fixed parent.  No clk_set_parent support
 */

#define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)

#define div_mask(d)     ((1 << ((d)->width)) - 1)

static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
{
        unsigned int maxdiv = 0;
        const struct clk_div_table *clkt;

        for (clkt = table; clkt->div; clkt++)
                if (clkt->div > maxdiv)
                        maxdiv = clkt->div;
        return maxdiv;
}

static unsigned int _get_maxdiv(struct clk_divider *divider)
{
        if (divider->flags & CLK_DIVIDER_ONE_BASED)
                return div_mask(divider);
        if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
                return 1 << div_mask(divider);
        if (divider->table)
                return _get_table_maxdiv(divider->table);
        return div_mask(divider) + 1;
}

static unsigned int _get_table_div(const struct clk_div_table *table,
                                                        unsigned int val)
{
        const struct clk_div_table *clkt;

        for (clkt = table; clkt->div; clkt++)
                if (clkt->val == val)
                        return clkt->div;
        return 0;
}

static unsigned int _get_div(struct clk_divider *divider, unsigned int val)
{
        if (divider->flags & CLK_DIVIDER_ONE_BASED)
                return val;
        if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
                return 1 << val;
        if (divider->table)
                return _get_table_div(divider->table, val);
        return val + 1;
}

static unsigned int _get_table_val(const struct clk_div_table *table,
                                                        unsigned int div)
{
        const struct clk_div_table *clkt;

        for (clkt = table; clkt->div; clkt++)
                if (clkt->div == div)
                        return clkt->val;
        return 0;
}

static unsigned int _get_val(struct clk_divider *divider, u8 div)
{
        if (divider->flags & CLK_DIVIDER_ONE_BASED)
                return div;
        if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
                return __ffs(div);
        if (divider->table)
                return  _get_table_val(divider->table, div);
        return div - 1;
}

static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
{
        struct clk_divider *divider = to_clk_divider(hw);
        unsigned int div, val;

        val = clk_readl(divider->reg) >> divider->shift;
        val &= div_mask(divider);

        div = _get_div(divider, val);
        if (!div) {
                WARN(!(divider->flags & CLK_DIVIDER_ALLOW_ZERO),
                        "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
                        __clk_get_name(hw->clk));
                return parent_rate;
        }

        return parent_rate / div;
}

/*
 * The reverse of DIV_ROUND_UP: The maximum number which
 * divided by m is r
 */
#define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)

static bool _is_valid_table_div(const struct clk_div_table *table,
                                                         unsigned int div)
{
        const struct clk_div_table *clkt;

        for (clkt = table; clkt->div; clkt++)
                if (clkt->div == div)
                        return true;
        return false;
}

static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
{
        if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
                return is_power_of_2(div);
        if (divider->table)
                return _is_valid_table_div(divider->table, div);
        return true;
}

static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
                unsigned long *best_parent_rate)
{
        struct clk_divider *divider = to_clk_divider(hw);
        int i, bestdiv = 0;
        unsigned long parent_rate, best = 0, now, maxdiv;

        if (!rate)
                rate = 1;

        maxdiv = _get_maxdiv(divider);

        if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
                parent_rate = *best_parent_rate;
                bestdiv = DIV_ROUND_UP(parent_rate, rate);
                bestdiv = bestdiv == 0 ? 1 : bestdiv;
                bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
                return bestdiv;
        }

        /*
         * The maximum divider we can use without overflowing
         * unsigned long in rate * i below
         */
        maxdiv = min(ULONG_MAX / rate, maxdiv);

        for (i = 1; i <= maxdiv; i++) {
                if (!_is_valid_div(divider, i))
                        continue;
                parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
                                MULT_ROUND_UP(rate, i));
                now = parent_rate / i;
                if (now <= rate && now > best) {
                        bestdiv = i;
                        best = now;
                        *best_parent_rate = parent_rate;
                }
        }

        if (!bestdiv) {
                bestdiv = _get_maxdiv(divider);
                *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
        }

        return bestdiv;
}

static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long *prate)
{
        int div;
        div = clk_divider_bestdiv(hw, rate, prate);

        return *prate / div;
}

static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long parent_rate)
{
        struct clk_divider *divider = to_clk_divider(hw);
        unsigned int div, value;
        unsigned long flags = 0;
        u32 val;

        div = parent_rate / rate;
        value = _get_val(divider, div);

        if (value > div_mask(divider))
                value = div_mask(divider);

        if (divider->lock)
                spin_lock_irqsave(divider->lock, flags);

        val = clk_readl(divider->reg);
        val &= ~(div_mask(divider) << divider->shift);
        val |= value << divider->shift;
        clk_writel(val, divider->reg);

        if (divider->lock)
                spin_unlock_irqrestore(divider->lock, flags);

        return 0;
}

const struct clk_ops clk_divider_ops = {
        .recalc_rate = clk_divider_recalc_rate,
        .round_rate = clk_divider_round_rate,
        .set_rate = clk_divider_set_rate,
};
EXPORT_SYMBOL_GPL(clk_divider_ops);

static struct clk *_register_divider(struct device *dev, const char *name,
                const char *parent_name, unsigned long flags,
                void __iomem *reg, u8 shift, u8 width,
                u8 clk_divider_flags, const struct clk_div_table *table,
                spinlock_t *lock)
{
        struct clk_divider *div;
        struct clk *clk;
        struct clk_init_data init;

        /* allocate the divider */
        div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
        if (!div) {
                pr_err("%s: could not allocate divider clk\n", __func__);
                return ERR_PTR(-ENOMEM);
        }

        init.name = name;
        init.ops = &clk_divider_ops;
        init.flags = flags | CLK_IS_BASIC;
        init.parent_names = (parent_name ? &parent_name: NULL);
        init.num_parents = (parent_name ? 1 : 0);

        /* struct clk_divider assignments */
        div->reg = reg;
        div->shift = shift;
        div->width = width;
        div->flags = clk_divider_flags;
        div->lock = lock;
        div->hw.init = &init;
        div->table = table;

        /* register the clock */
        clk = clk_register(dev, &div->hw);

        if (IS_ERR(clk))
                kfree(div);

        return clk;
}

/**
 * clk_register_divider - register a divider clock with the clock framework
 * @dev: device registering this clock
 * @name: name of this clock
 * @parent_name: name of clock's parent
 * @flags: framework-specific flags
 * @reg: register address to adjust divider
 * @shift: number of bits to shift the bitfield
 * @width: width of the bitfield
 * @clk_divider_flags: divider-specific flags for this clock
 * @lock: shared register lock for this clock
 */
struct clk *clk_register_divider(struct device *dev, const char *name,
                const char *parent_name, unsigned long flags,
                void __iomem *reg, u8 shift, u8 width,
                u8 clk_divider_flags, spinlock_t *lock)
{
        return _register_divider(dev, name, parent_name, flags, reg, shift,
                        width, clk_divider_flags, NULL, lock);
}

/**
 * clk_register_divider_table - register a table based divider clock with
 * the clock framework
 * @dev: device registering this clock
 * @name: name of this clock
 * @parent_name: name of clock's parent
 * @flags: framework-specific flags
 * @reg: register address to adjust divider
 * @shift: number of bits to shift the bitfield
 * @width: width of the bitfield
 * @clk_divider_flags: divider-specific flags for this clock
 * @table: array of divider/value pairs ending with a div set to 0
 * @lock: shared register lock for this clock
 */
struct clk *clk_register_divider_table(struct device *dev, const char *name,
                const char *parent_name, unsigned long flags,
                void __iomem *reg, u8 shift, u8 width,
                u8 clk_divider_flags, const struct clk_div_table *table,
                spinlock_t *lock)
{
        return _register_divider(dev, name, parent_name, flags, reg, shift,
                        width, clk_divider_flags, table, lock);
}