/*
 * clkt_clksel.c - OMAP2/3/4 clksel clock functions
 *
 * Copyright (C) 2005-2008 Texas Instruments, Inc.
 * Copyright (C) 2004-2010 Nokia Corporation
 *
 * Contacts:
 * Richard Woodruff <r-woodruff2@ti.com>
 * Paul Walmsley
 *
 * 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.
 *
 * XXX At some point these clksel clocks should be split into
 * "divider" clocks and "mux" clocks to better match the hardware.
 *
 * XXX Currently these clocks are only used in the OMAP2/3/4 code, but
 * many of the OMAP1 clocks should be convertible to use this
 * mechanism.
 */
#undef DEBUG

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/clk.h>
#include <linux/io.h>

#include <plat/clock.h>

#include "clock.h"
#include "cm.h"
#include "cm-regbits-24xx.h"
#include "cm-regbits-34xx.h"

/* Private functions */

/**
 * _omap2_get_clksel_by_parent - return clksel struct for a given clk & parent
 * @clk: OMAP struct clk ptr to inspect
 * @src_clk: OMAP struct clk ptr of the parent clk to search for
 *
 * Scan the struct clksel array associated with the clock to find
 * the element associated with the supplied parent clock address.
 * Returns a pointer to the struct clksel on success or NULL on error.
 */
static const struct clksel *_omap2_get_clksel_by_parent(struct clk *clk,
							struct clk *src_clk)
{
	const struct clksel *clks;

	if (!clk->clksel)
		return NULL;

	for (clks = clk->clksel; clks->parent; clks++) {
		if (clks->parent == src_clk)
			break; /* Found the requested parent */
	}

	if (!clks->parent) {
		printk(KERN_ERR "clock: Could not find parent clock %s in "
		       "clksel array of clock %s\n", src_clk->name,
		       clk->name);
		return NULL;
	}

	return clks;
}

/**
 * _omap2_clksel_get_src_field - find the new clksel divisor to use
 * @src_clk: planned new parent struct clk *
 * @clk: struct clk * that is being reparented
 * @field_val: pointer to a u32 to contain the register data for the divisor
 *
 * Given an intended new parent struct clk * @src_clk, and the struct
 * clk * @clk to the clock that is being reparented, find the
 * appropriate rate divisor for the new clock (returned as the return
 * value), and the corresponding register bitfield data to program to
 * reach that divisor (returned in the u32 pointed to by @field_val).
 * Returns 0 on error, or returns the newly-selected divisor upon
 * success (in this latter case, the corresponding register bitfield
 * value is passed back in the variable pointed to by @field_val)
 */
static u8 _omap2_clksel_get_src_field(struct clk *src_clk, struct clk *clk,
				      u32 *field_val)
{
	const struct clksel *clks;
	const struct clksel_rate *clkr, *max_clkr;
	u8 max_div = 0;

	clks = _omap2_get_clksel_by_parent(clk, src_clk);
	if (!clks)
		return 0;

	/*
	 * Find the highest divisor (e.g., the one resulting in the
	 * lowest rate) to use as the default.  This should avoid
	 * clock rates that are too high for the device.  XXX A better
	 * solution here would be to try to determine if there is a
	 * divisor matching the original clock rate before the parent
	 * switch, and if it cannot be found, to fall back to the
	 * highest divisor.
	 */
	for (clkr = clks->rates; clkr->div; clkr++) {
		if (!(clkr->flags & cpu_mask))
			continue;

		if (clkr->div > max_div) {
			max_div = clkr->div;
			max_clkr = clkr;
		}
	}

	if (max_div == 0) {
		WARN(1, "clock: Could not find divisor for "
		       "clock %s parent %s\n", clk->name,
		       src_clk->parent->name);
		return 0;
	}

	*field_val = max_clkr->val;

	return max_div;
}


/* Public functions */

/**
 * omap2_init_clksel_parent - set a clksel clk's parent field from the hardware
 * @clk: OMAP clock struct ptr to use
 *
 * Given a pointer to a source-selectable struct clk, read the hardware
 * register and determine what its parent is currently set to.  Update the
 * clk->parent field with the appropriate clk ptr.
 */
void omap2_init_clksel_parent(struct clk *clk)
{
	const struct clksel *clks;
	const struct clksel_rate *clkr;
	u32 r, found = 0;

	if (!clk->clksel)
		return;

	r = __raw_readl(clk->clksel_reg) & clk->clksel_mask;
	r >>= __ffs(clk->clksel_mask);

	for (clks = clk->clksel; clks->parent && !found; clks++) {
		for (clkr = clks->rates; clkr->div && !found; clkr++) {
			if ((clkr->flags & cpu_mask) && (clkr->val == r)) {
				if (clk->parent != clks->parent) {
					pr_debug("clock: inited %s parent "
						 "to %s (was %s)\n",
						 clk->name, clks->parent->name,
						 ((clk->parent) ?
						  clk->parent->name : "NULL"));
					clk_reparent(clk, clks->parent);
				};
				found = 1;
			}
		}
	}

	if (!found)
		printk(KERN_ERR "clock: init parent: could not find "
		       "regval %0x for clock %s\n", r,  clk->name);

	return;
}

/*
 * Used for clocks that are part of CLKSEL_xyz governed clocks.
 * REVISIT: Maybe change to use clk->enable() functions like on omap1?
 */
unsigned long omap2_clksel_recalc(struct clk *clk)
{
	unsigned long rate;
	u32 div = 0;

	pr_debug("clock: recalc'ing clksel clk %s\n", clk->name);

	div = omap2_clksel_get_divisor(clk);
	if (div == 0)
		return clk->rate;

	rate = clk->parent->rate / div;

	pr_debug("clock: new clock rate is %ld (div %d)\n", rate, div);

	return rate;
}

/**
 * omap2_clksel_round_rate_div - find divisor for the given clock and rate
 * @clk: OMAP struct clk to use
 * @target_rate: desired clock rate
 * @new_div: ptr to where we should store the divisor
 *
 * Finds 'best' divider value in an array based on the source and target
 * rates.  The divider array must be sorted with smallest divider first.
 *
 * Returns the rounded clock rate or returns 0xffffffff on error.
 */
u32 omap2_clksel_round_rate_div(struct clk *clk, unsigned long target_rate,
				u32 *new_div)
{
	unsigned long test_rate;
	const struct clksel *clks;
	const struct clksel_rate *clkr;
	u32 last_div = 0;

	pr_debug("clock: clksel_round_rate_div: %s target_rate %ld\n",
		 clk->name, target_rate);

	*new_div = 1;

	clks = _omap2_get_clksel_by_parent(clk, clk->parent);
	if (!clks)
		return ~0;

	for (clkr = clks->rates; clkr->div; clkr++) {
		if (!(clkr->flags & cpu_mask))
			continue;

		/* Sanity check */
		if (clkr->div <= last_div)
			pr_err("clock: clksel_rate table not sorted "
			       "for clock %s", clk->name);

		last_div = clkr->div;

		test_rate = clk->parent->rate / clkr->div;

		if (test_rate <= target_rate)
			break; /* found it */
	}

	if (!clkr->div) {
		pr_err("clock: Could not find divisor for target "
		       "rate %ld for clock %s parent %s\n", target_rate,
		       clk->name, clk->parent->name);
		return ~0;
	}

	*new_div = clkr->div;

	pr_debug("clock: new_div = %d, new_rate = %ld\n", *new_div,
		 (clk->parent->rate / clkr->div));

	return clk->parent->rate / clkr->div;
}

/**
 * omap2_clksel_round_rate - find rounded rate for the given clock and rate
 * @clk: OMAP struct clk to use
 * @target_rate: desired clock rate
 *
 * Compatibility wrapper for OMAP clock framework
 * Finds best target rate based on the source clock and possible dividers.
 * rates. The divider array must be sorted with smallest divider first.
 * Note that this will not work for clocks which are part of CONFIG_PARTICIPANT,
 * they are only settable as part of virtual_prcm set.
 *
 * Returns the rounded clock rate or returns 0xffffffff on error.
 */
long omap2_clksel_round_rate(struct clk *clk, unsigned long target_rate)
{
	u32 new_div;

	return omap2_clksel_round_rate_div(clk, target_rate, &new_div);
}


/* Given a clock and a rate apply a clock specific rounding function */
long omap2_clk_round_rate(struct clk *clk, unsigned long rate)
{
	if (clk->round_rate)
		return clk->round_rate(clk, rate);

	return clk->rate;
}

/**
 * omap2_clksel_to_divisor() - turn clksel field value into integer divider
 * @clk: OMAP struct clk to use
 * @field_val: register field value to find
 *
 * Given a struct clk of a rate-selectable clksel clock, and a register field
 * value to search for, find the corresponding clock divisor.  The register
 * field value should be pre-masked and shifted down so the LSB is at bit 0
 * before calling.  Returns 0 on error
 */
u32 omap2_clksel_to_divisor(struct clk *clk, u32 field_val)
{
	const struct clksel *clks;
	const struct clksel_rate *clkr;

	clks = _omap2_get_clksel_by_parent(clk, clk->parent);
	if (!clks)
		return 0;

	for (clkr = clks->rates; clkr->div; clkr++) {
		if ((clkr->flags & cpu_mask) && (clkr->val == field_val))
			break;
	}

	if (!clkr->div) {
		printk(KERN_ERR "clock: Could not find fieldval %d for "
		       "clock %s parent %s\n", field_val, clk->name,
		       clk->parent->name);
		return 0;
	}

	return clkr->div;
}

/**
 * omap2_divisor_to_clksel() - turn clksel integer divisor into a field value
 * @clk: OMAP struct clk to use
 * @div: integer divisor to search for
 *
 * Given a struct clk of a rate-selectable clksel clock, and a clock divisor,
 * find the corresponding register field value.  The return register value is
 * the value before left-shifting.  Returns ~0 on error
 */
u32 omap2_divisor_to_clksel(struct clk *clk, u32 div)
{
	const struct clksel *clks;
	const struct clksel_rate *clkr;

	/* should never happen */
	WARN_ON(div == 0);

	clks = _omap2_get_clksel_by_parent(clk, clk->parent);
	if (!clks)
		return ~0;

	for (clkr = clks->rates; clkr->div; clkr++) {
		if ((clkr->flags & cpu_mask) && (clkr->div == div))
			break;
	}

	if (!clkr->div) {
		printk(KERN_ERR "clock: Could not find divisor %d for "
		       "clock %s parent %s\n", div, clk->name,
		       clk->parent->name);
		return ~0;
	}

	return clkr->val;
}

/**
 * omap2_clksel_get_divisor - get current divider applied to parent clock.
 * @clk: OMAP struct clk to use.
 *
 * Returns the integer divisor upon success or 0 on error.
 */
u32 omap2_clksel_get_divisor(struct clk *clk)
{
	u32 v;

	if (!clk->clksel_mask)
		return 0;

	v = __raw_readl(clk->clksel_reg) & clk->clksel_mask;
	v >>= __ffs(clk->clksel_mask);

	return omap2_clksel_to_divisor(clk, v);
}

int omap2_clksel_set_rate(struct clk *clk, unsigned long rate)
{
	u32 v, field_val, validrate, new_div = 0;

	if (!clk->clksel_mask)
		return -EINVAL;

	validrate = omap2_clksel_round_rate_div(clk, rate, &new_div);
	if (validrate != rate)
		return -EINVAL;

	field_val = omap2_divisor_to_clksel(clk, new_div);
	if (field_val == ~0)
		return -EINVAL;

	v = __raw_readl(clk->clksel_reg);
	v &= ~clk->clksel_mask;
	v |= field_val << __ffs(clk->clksel_mask);
	__raw_writel(v, clk->clksel_reg);
	v = __raw_readl(clk->clksel_reg); /* OCP barrier */

	clk->rate = clk->parent->rate / new_div;

	return 0;
}

int omap2_clksel_set_parent(struct clk *clk, struct clk *new_parent)
{
	u32 field_val, v, parent_div;

	if (!clk->clksel || !clk->clksel_mask)
		return -EINVAL;

	parent_div = _omap2_clksel_get_src_field(new_parent, clk, &field_val);
	if (!parent_div)
		return -EINVAL;

	/* Set new source value (previous dividers if any in effect) */
	v = __raw_readl(clk->clksel_reg);
	v &= ~clk->clksel_mask;
	v |= field_val << __ffs(clk->clksel_mask);
	__raw_writel(v, clk->clksel_reg);
	v = __raw_readl(clk->clksel_reg);    /* OCP barrier */

	clk_reparent(clk, new_parent);

	/* CLKSEL clocks follow their parents' rates, divided by a divisor */
	clk->rate = new_parent->rate;

	if (parent_div > 0)
		clk->rate /= parent_div;

	pr_debug("clock: set parent of %s to %s (new rate %ld)\n",
		 clk->name, clk->parent->name, clk->rate);

	return 0;
}