barebox/drivers/clk/clk-divider.c

/*
 * clk-divider.c - generic barebox clock support. Based on Linux clk support
 *
 * Copyright (c) 2012 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
 *
 * 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.
 *
 * 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 <common.h>
#include <io.h>
#include <malloc.h>
#include <linux/clk.h>
#include <linux/err.h>

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

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

static unsigned long clk_divider_recalc_rate(struct clk *clk,
		unsigned long parent_rate)
{
	struct clk_divider *divider = container_of(clk, struct clk_divider, clk);
	unsigned int div, val;

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

	div = _get_div(divider, val);

	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->table)
		return _is_valid_table_div(divider->table, div);
	return true;
}

static int clk_divider_bestdiv(struct clk *clk, unsigned long rate,
		unsigned long *best_parent_rate)
{
	struct clk_divider *divider = container_of(clk, struct clk_divider, clk);
	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(divider);

	if (!(clk->flags & 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;
		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_round_rate(clk_get_parent(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(clk), 1);
	}

	return bestdiv;
}

static long clk_divider_round_rate(struct clk *clk, unsigned long rate,
		unsigned long *parent_rate)
{
	int div;

	div = clk_divider_bestdiv(clk, rate, parent_rate);

	return *parent_rate / div;
}

static int clk_divider_set_rate(struct clk *clk, unsigned long rate,
		unsigned long parent_rate)
{
	struct clk_divider *divider = container_of(clk, struct clk_divider, clk);
	unsigned int div, value;
	u32 val;

	if (clk->flags & CLK_SET_RATE_PARENT) {
		unsigned long best_parent_rate = parent_rate;
		div = clk_divider_bestdiv(clk, rate, &best_parent_rate);
		clk_set_rate(clk_get_parent(clk), best_parent_rate);
	} else {
		div = parent_rate / rate;
	}

	value = _get_val(divider, div);

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

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

	return 0;
}

struct clk_ops clk_divider_ops = {
	.set_rate = clk_divider_set_rate,
	.recalc_rate = clk_divider_recalc_rate,
	.round_rate = clk_divider_round_rate,
};

struct clk *clk_divider(const char *name, const char *parent,
		void __iomem *reg, u8 shift, u8 width, unsigned flags)
{
	struct clk_divider *div = xzalloc(sizeof(*div));
	int ret;

	div->shift = shift;
	div->reg = reg;
	div->width = width;
	div->parent = parent;
	div->clk.ops = &clk_divider_ops;
	div->clk.name = name;
	div->clk.flags = flags;
	div->clk.parent_names = &div->parent;
	div->clk.num_parents = 1;

	ret = clk_register(&div->clk);
	if (ret) {
		free(div);
		return ERR_PTR(ret);
	}

	return &div->clk;
}

struct clk *clk_divider_one_based(const char *name, const char *parent,
		void __iomem *reg, u8 shift, u8 width, unsigned flags)
{
	struct clk_divider *div;
	struct clk *clk;

	clk = clk_divider(name, parent, reg, shift, width, flags);
	if (IS_ERR(clk))
		return clk;

	div = container_of(clk, struct clk_divider, clk);
	div->flags |= CLK_DIVIDER_ONE_BASED;

	return clk;
}

struct clk *clk_divider_table(const char *name,
		const char *parent, void __iomem *reg, u8 shift, u8 width,
		const struct clk_div_table *table, unsigned flags)
{
	struct clk_divider *div = xzalloc(sizeof(*div));
	const struct clk_div_table *clkt;
	int ret, max_div = 0;

	div->shift = shift;
	div->reg = reg;
	div->width = width;
	div->parent = parent;
	div->clk.ops = &clk_divider_ops;
	div->clk.name = name;
	div->clk.flags = flags;
	div->clk.parent_names = &div->parent;
	div->clk.num_parents = 1;
	div->table = table;

	for (clkt = div->table; clkt->div; clkt++) {
		if (clkt->div > max_div) {
			max_div = clkt->div;
			div->max_div_index = div->table_size;
		}
		div->table_size++;
	}

	ret = clk_register(&div->clk);
	if (ret) {
		free(div);
		return ERR_PTR(ret);
	}

	return &div->clk;
}