/*
 * 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 = ceiling(parent->rate / divisor)
 * parent - fixed parent.  No clk_set_parent support
 */

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

static unsigned int _get_table_maxdiv(const struct clk_div_table *table,
                                      u8 width)
{
        unsigned int maxdiv = 0, mask = div_mask(width);
        const struct clk_div_table *clkt;

        for (clkt = table; clkt->div; clkt++)
                if (clkt->div > maxdiv && clkt->val <= mask)
                        maxdiv = clkt->div;
        return maxdiv;
}

static unsigned int _get_table_mindiv(const struct clk_div_table *table)
{
        unsigned int mindiv = UINT_MAX;
        const struct clk_div_table *clkt;

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

static unsigned int _get_maxdiv(const struct clk_div_table *table, u8 width,
                                unsigned long flags)
{
        if (flags & CLK_DIVIDER_ONE_BASED)
                return div_mask(width);
        if (flags & CLK_DIVIDER_POWER_OF_TWO)
                return 1 << div_mask(width);
        if (table)
                return _get_table_maxdiv(table, width);
        return div_mask(width) + 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(const struct clk_div_table *table,
                             unsigned int val, unsigned long flags, u8 width)
{
        if (flags & CLK_DIVIDER_ONE_BASED)
                return val;
        if (flags & CLK_DIVIDER_POWER_OF_TWO)
                return 1 << val;
        if (flags & CLK_DIVIDER_MAX_AT_ZERO)
                return val ? val : div_mask(width) + 1;
        if (table)
                return _get_table_div(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(const struct clk_div_table *table,
                             unsigned int div, unsigned long flags, u8 width)
{
        if (flags & CLK_DIVIDER_ONE_BASED)
                return div;
        if (flags & CLK_DIVIDER_POWER_OF_TWO)
                return __ffs(div);
        if (flags & CLK_DIVIDER_MAX_AT_ZERO)
                return (div == div_mask(width) + 1) ? 0 : div;
        if (table)
                return  _get_table_val(table, div);
        return div - 1;
}

unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
                                  unsigned int val,
                                  const struct clk_div_table *table,
                                  unsigned long flags)
{
        struct clk_divider *divider = to_clk_divider(hw);
        unsigned int div;

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

        return DIV_ROUND_UP_ULL((u64)parent_rate, div);
}
EXPORT_SYMBOL_GPL(divider_recalc_rate);

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 val;

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

        return divider_recalc_rate(hw, parent_rate, val, divider->table,
                                   divider->flags);
}

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(const struct clk_div_table *table, unsigned int div,
                          unsigned long flags)
{
        if (flags & CLK_DIVIDER_POWER_OF_TWO)
                return is_power_of_2(div);
        if (table)
                return _is_valid_table_div(table, div);
        return true;
}

static int _round_up_table(const struct clk_div_table *table, int div)
{
        const struct clk_div_table *clkt;
        int up = INT_MAX;

        for (clkt = table; clkt->div; clkt++) {
                if (clkt->div == div)
                        return clkt->div;
                else if (clkt->div < div)
                        continue;

                if ((clkt->div - div) < (up - div))
                        up = clkt->div;
        }

        return up;
}

static int _round_down_table(const struct clk_div_table *table, int div)
{
        const struct clk_div_table *clkt;
        int down = _get_table_mindiv(table);

        for (clkt = table; clkt->div; clkt++) {
                if (clkt->div == div)
                        return clkt->div;
                else if (clkt->div > div)
                        continue;

                if ((div - clkt->div) < (div - down))
                        down = clkt->div;
        }

        return down;
}

static int _div_round_up(const struct clk_div_table *table,
                         unsigned long parent_rate, unsigned long rate,
                         unsigned long flags)
{
        int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);

        if (flags & CLK_DIVIDER_POWER_OF_TWO)
                div = __roundup_pow_of_two(div);
        if (table)
                div = _round_up_table(table, div);

        return div;
}

static int _div_round_closest(const struct clk_div_table *table,
                              unsigned long parent_rate, unsigned long rate,
                              unsigned long flags)
{
        int up, down;
        unsigned long up_rate, down_rate;

        up = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
        down = parent_rate / rate;

        if (flags & CLK_DIVIDER_POWER_OF_TWO) {
                up = __roundup_pow_of_two(up);
                down = __rounddown_pow_of_two(down);
        } else if (table) {
                up = _round_up_table(table, up);
                down = _round_down_table(table, down);
        }

        up_rate = DIV_ROUND_UP_ULL((u64)parent_rate, up);
        down_rate = DIV_ROUND_UP_ULL((u64)parent_rate, down);

        return (rate - up_rate) <= (down_rate - rate) ? up : down;
}

static int _div_round(const struct clk_div_table *table,
                      unsigned long parent_rate, unsigned long rate,
                      unsigned long flags)
{
        if (flags & CLK_DIVIDER_ROUND_CLOSEST)
                return _div_round_closest(table, parent_rate, rate, flags);

        return _div_round_up(table, parent_rate, rate, flags);
}

static bool _is_best_div(unsigned long rate, unsigned long now,
                         unsigned long best, unsigned long flags)
{
        if (flags & CLK_DIVIDER_ROUND_CLOSEST)
                return abs(rate - now) < abs(rate - best);

        return now <= rate && now > best;
}

static int _next_div(const struct clk_div_table *table, int div,
                     unsigned long flags)
{
        div++;

        if (flags & CLK_DIVIDER_POWER_OF_TWO)
                return __roundup_pow_of_two(div);
        if (table)
                return _round_up_table(table, div);

        return div;
}

static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
                               unsigned long *best_parent_rate,
                               const struct clk_div_table *table, u8 width,
                               unsigned long flags)
{
        int i, bestdiv = 0;
        unsigned long parent_rate, best = 0, now, maxdiv;
        unsigned long parent_rate_saved = *best_parent_rate;

        if (!rate)
                rate = 1;

        maxdiv = _get_maxdiv(table, width, flags);

        if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
                parent_rate = *best_parent_rate;
                bestdiv = _div_round(table, parent_rate, rate, flags);
                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 = _next_div(table, 0, flags); i <= maxdiv;
                                             i = _next_div(table, i, flags)) {
                if (rate * i == parent_rate_saved) {
                        /*
                         * It's the most ideal case if the requested rate can be
                         * divided from parent clock without needing to change
                         * parent rate, so return the divider immediately.
                         */
                        *best_parent_rate = parent_rate_saved;
                        return i;
                }
                parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw),
                                               rate * i);
                now = DIV_ROUND_UP_ULL((u64)parent_rate, i);
                if (_is_best_div(rate, now, best, flags)) {
                        bestdiv = i;
                        best = now;
                        *best_parent_rate = parent_rate;
                }
        }

        if (!bestdiv) {
                bestdiv = _get_maxdiv(table, width, flags);
                *best_parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw), 1);
        }

        return bestdiv;
}

long divider_round_rate(struct clk_hw *hw, unsigned long rate,
                        unsigned long *prate, const struct clk_div_table *table,
                        u8 width, unsigned long flags)
{
        int div;

        div = clk_divider_bestdiv(hw, rate, prate, table, width, flags);

        return DIV_ROUND_UP_ULL((u64)*prate, div);
}
EXPORT_SYMBOL_GPL(divider_round_rate);

static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long *prate)
{
        struct clk_divider *divider = to_clk_divider(hw);
        int bestdiv;

        /* if read only, just return current value */
        if (divider->flags & CLK_DIVIDER_READ_ONLY) {
                bestdiv = readl(divider->reg) >> divider->shift;
                bestdiv &= div_mask(divider->width);
                bestdiv = _get_div(divider->table, bestdiv, divider->flags,
                        divider->width);
                return DIV_ROUND_UP_ULL((u64)*prate, bestdiv);
        }

        return divider_round_rate(hw, rate, prate, divider->table,
                                  divider->width, divider->flags);
}

int divider_get_val(unsigned long rate, unsigned long parent_rate,
                    const struct clk_div_table *table, u8 width,
                    unsigned long flags)
{
        unsigned int div, value;

        div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);

        if (!_is_valid_div(table, div, flags))
                return -EINVAL;

        value = _get_val(table, div, flags, width);

        return min_t(unsigned int, value, div_mask(width));
}
EXPORT_SYMBOL_GPL(divider_get_val);

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 value;
        unsigned long flags = 0;
        u32 val;

        value = divider_get_val(rate, parent_rate, divider->table,
                                divider->width, divider->flags);

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

        if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
                val = div_mask(divider->width) << (divider->shift + 16);
        } else {
                val = clk_readl(divider->reg);
                val &= ~(div_mask(divider->width) << divider->shift);
        }
        val |= value << divider->shift;
        clk_writel(val, divider->reg);

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

        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);

const struct clk_ops clk_divider_ro_ops = {
        .recalc_rate = clk_divider_recalc_rate,
        .round_rate = clk_divider_round_rate,
};
EXPORT_SYMBOL_GPL(clk_divider_ro_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;

        if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
                if (width + shift > 16) {
                        pr_warn("divider value exceeds LOWORD field\n");
                        return ERR_PTR(-EINVAL);
                }
        }

        /* allocate the divider */
        div = kzalloc(sizeof(*div), GFP_KERNEL);
        if (!div)
                return ERR_PTR(-ENOMEM);

        init.name = name;
        if (clk_divider_flags & CLK_DIVIDER_READ_ONLY)
                init.ops = &clk_divider_ro_ops;
        else
                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);
}
EXPORT_SYMBOL_GPL(clk_register_divider);

/**
 * 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);
}
EXPORT_SYMBOL_GPL(clk_register_divider_table);

void clk_unregister_divider(struct clk *clk)
{
        struct clk_divider *div;
        struct clk_hw *hw;

        hw = __clk_get_hw(clk);
        if (!hw)
                return;

        div = to_clk_divider(hw);

        clk_unregister(clk);
        kfree(div);
}
EXPORT_SYMBOL_GPL(clk_unregister_divider);