/*
 * Copyright (C) 2013 Emilio López <emilio@elopez.com.ar>
 *
 * 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 factor-based 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/delay.h>

#include "clk-factors.h"

/*
 * DOC: basic adjustable factor-based 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 * N * (K + 1) >> P) / (M + 1)
 * parent - fixed parent.  No clk_set_parent support
 */

#define to_clk_factors(_hw) container_of(_hw, struct clk_factors, hw)

#define SETMASK(len, pos)		(((1U << (len)) - 1) << (pos))
#define CLRMASK(len, pos)		(~(SETMASK(len, pos)))
#define FACTOR_GET(bit, len, reg)	(((reg) & SETMASK(len, bit)) >> (bit))

#define FACTOR_SET(bit, len, reg, val) \
	(((reg) & CLRMASK(len, bit)) | (val << (bit)))

static unsigned long clk_factors_recalc_rate(struct clk_hw *hw,
					     unsigned long parent_rate)
{
	u8 n = 1, k = 0, p = 0, m = 0;
	u32 reg;
	unsigned long rate;
	struct clk_factors *factors = to_clk_factors(hw);
	struct clk_factors_config *config = factors->config;

	/* Fetch the register value */
	reg = readl(factors->reg);

	/* Get each individual factor if applicable */
	if (config->nwidth != SUNXI_FACTORS_NOT_APPLICABLE)
		n = FACTOR_GET(config->nshift, config->nwidth, reg);
	if (config->kwidth != SUNXI_FACTORS_NOT_APPLICABLE)
		k = FACTOR_GET(config->kshift, config->kwidth, reg);
	if (config->mwidth != SUNXI_FACTORS_NOT_APPLICABLE)
		m = FACTOR_GET(config->mshift, config->mwidth, reg);
	if (config->pwidth != SUNXI_FACTORS_NOT_APPLICABLE)
		p = FACTOR_GET(config->pshift, config->pwidth, reg);

	/* Calculate the rate */
	rate = (parent_rate * n * (k + 1) >> p) / (m + 1);

	return rate;
}

static long clk_factors_round_rate(struct clk_hw *hw, unsigned long rate,
				   unsigned long *parent_rate)
{
	struct clk_factors *factors = to_clk_factors(hw);
	factors->get_factors((u32 *)&rate, (u32)*parent_rate,
			     NULL, NULL, NULL, NULL);

	return rate;
}

static long clk_factors_determine_rate(struct clk_hw *hw, unsigned long rate,
				       unsigned long *best_parent_rate,
				       struct clk **best_parent_p)
{
	struct clk *clk = hw->clk, *parent, *best_parent = NULL;
	int i, num_parents;
	unsigned long parent_rate, best = 0, child_rate, best_child_rate = 0;

	/* find the parent that can help provide the fastest rate <= rate */
	num_parents = __clk_get_num_parents(clk);
	for (i = 0; i < num_parents; i++) {
		parent = clk_get_parent_by_index(clk, i);
		if (!parent)
			continue;
		if (__clk_get_flags(clk) & CLK_SET_RATE_PARENT)
			parent_rate = __clk_round_rate(parent, rate);
		else
			parent_rate = __clk_get_rate(parent);

		child_rate = clk_factors_round_rate(hw, rate, &parent_rate);

		if (child_rate <= rate && child_rate > best_child_rate) {
			best_parent = parent;
			best = parent_rate;
			best_child_rate = child_rate;
		}
	}

	if (best_parent)
		*best_parent_p = best_parent;
	*best_parent_rate = best;

	return best_child_rate;
}

static int clk_factors_set_rate(struct clk_hw *hw, unsigned long rate,
				unsigned long parent_rate)
{
	u8 n = 0, k = 0, m = 0, p = 0;
	u32 reg;
	struct clk_factors *factors = to_clk_factors(hw);
	struct clk_factors_config *config = factors->config;
	unsigned long flags = 0;

	factors->get_factors((u32 *)&rate, (u32)parent_rate, &n, &k, &m, &p);

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

	/* Fetch the register value */
	reg = readl(factors->reg);

	/* Set up the new factors - macros do not do anything if width is 0 */
	reg = FACTOR_SET(config->nshift, config->nwidth, reg, n);
	reg = FACTOR_SET(config->kshift, config->kwidth, reg, k);
	reg = FACTOR_SET(config->mshift, config->mwidth, reg, m);
	reg = FACTOR_SET(config->pshift, config->pwidth, reg, p);

	/* Apply them now */
	writel(reg, factors->reg);

	/* delay 500us so pll stabilizes */
	__delay((rate >> 20) * 500 / 2);

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

	return 0;
}

const struct clk_ops clk_factors_ops = {
	.determine_rate = clk_factors_determine_rate,
	.recalc_rate = clk_factors_recalc_rate,
	.round_rate = clk_factors_round_rate,
	.set_rate = clk_factors_set_rate,
};