/*
 * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
 *
 * 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.
 */

#include <linux/clk-provider.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/mfd/syscon.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/regmap.h>
#include <linux/slab.h>

#define PMU_XTAL_FREQ_RATIO			0x66c
#define  XTAL_ALP_PER_4ILP			0x00001fff
#define  XTAL_CTL_EN				0x80000000
#define PMU_SLOW_CLK_PERIOD			0x6dc

struct bcm53573_ilp {
	struct clk_hw hw;
	struct regmap *regmap;
};

static int bcm53573_ilp_enable(struct clk_hw *hw)
{
	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);

	regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0x10199);
	regmap_write(ilp->regmap, 0x674, 0x10000);

	return 0;
}

static void bcm53573_ilp_disable(struct clk_hw *hw)
{
	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);

	regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0);
	regmap_write(ilp->regmap, 0x674, 0);
}

static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
					      unsigned long parent_rate)
{
	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
	struct regmap *regmap = ilp->regmap;
	u32 last_val, cur_val;
	int sum = 0, num = 0, loop_num = 0;
	int avg;

	/* Enable measurement */
	regmap_write(regmap, PMU_XTAL_FREQ_RATIO, XTAL_CTL_EN);

	/* Read initial value */
	regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &last_val);
	last_val &= XTAL_ALP_PER_4ILP;

	/*
	 * At minimum we should loop for a bit to let hardware do the
	 * measurement. This isn't very accurate however, so for a better
	 * precision lets try getting 20 different values for and use average.
	 */
	while (num < 20) {
		regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &cur_val);
		cur_val &= XTAL_ALP_PER_4ILP;

		if (cur_val != last_val) {
			/* Got different value, use it */
			sum += cur_val;
			num++;
			loop_num = 0;
			last_val = cur_val;
		} else if (++loop_num > 5000) {
			/* Same value over and over, give up */
			sum += cur_val;
			num++;
			break;
		}

		cpu_relax();
	}

	/* Disable measurement to save power */
	regmap_write(regmap, PMU_XTAL_FREQ_RATIO, 0x0);

	avg = sum / num;

	return parent_rate * 4 / avg;
}

static const struct clk_ops bcm53573_ilp_clk_ops = {
	.enable = bcm53573_ilp_enable,
	.disable = bcm53573_ilp_disable,
	.recalc_rate = bcm53573_ilp_recalc_rate,
};

static void bcm53573_ilp_init(struct device_node *np)
{
	struct bcm53573_ilp *ilp;
	struct clk_init_data init = { };
	const char *parent_name;
	int err;

	ilp = kzalloc(sizeof(*ilp), GFP_KERNEL);
	if (!ilp)
		return;

	parent_name = of_clk_get_parent_name(np, 0);
	if (!parent_name) {
		err = -ENOENT;
		goto err_free_ilp;
	}

	ilp->regmap = syscon_node_to_regmap(of_get_parent(np));
	if (IS_ERR(ilp->regmap)) {
		err = PTR_ERR(ilp->regmap);
		goto err_free_ilp;
	}

	init.name = np->name;
	init.ops = &bcm53573_ilp_clk_ops;
	init.parent_names = &parent_name;
	init.num_parents = 1;

	ilp->hw.init = &init;
	err = clk_hw_register(NULL, &ilp->hw);
	if (err)
		goto err_free_ilp;

	err = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &ilp->hw);
	if (err)
		goto err_clk_hw_unregister;

	return;

err_clk_hw_unregister:
	clk_hw_unregister(&ilp->hw);
err_free_ilp:
	kfree(ilp);
	pr_err("Failed to init ILP clock: %d\n", err);
}

/* We need it very early for arch code, before device model gets ready */
CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);