drivers/clk/clk-si570.c - kernel/mindspeed - Git at Google

 /*
  * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
  *
  * Copyright (C) 2010, 2011 Ericsson AB.
  * Copyright (C) 2011 Guenter Roeck.
  * Copyright (C) 2011 - 2013 Xilinx Inc.
  *
  * Author: Guenter Roeck <guenter.roeck@ericsson.com>
  *	   Sören Brinkmann <soren.brinkmann@xilinx.com>
  *
  * 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 <linux/clk-provider.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/i2c.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>

 /* Si570 registers */
 #define SI570_REG_HS_N1		7
 #define SI570_REG_N1_RFREQ0	8
 #define SI570_REG_RFREQ1	9
 #define SI570_REG_RFREQ2	10
 #define SI570_REG_RFREQ3	11
 #define SI570_REG_RFREQ4	12
 #define SI570_REG_CONTROL	135
 #define SI570_REG_FREEZE_DCO	137
 #define SI570_DIV_OFFSET_7PPM	6

 #define HS_DIV_SHIFT		5
 #define HS_DIV_MASK		0xe0
 #define HS_DIV_OFFSET		4
 #define N1_6_2_MASK		0x1f
 #define N1_1_0_MASK		0xc0
 #define RFREQ_37_32_MASK	0x3f

 #define SI570_MIN_FREQ		10000000L
 #define SI570_MAX_FREQ		1417500000L
 #define SI598_MAX_FREQ		525000000L

 #define FDCO_MIN		4850000000LL
 #define FDCO_MAX		5670000000LL

 #define SI570_CNTRL_RECALL	(1 << 0)
 #define SI570_CNTRL_FREEZE_M	(1 << 5)
 #define SI570_CNTRL_NEWFREQ	(1 << 6)

 #define SI570_FREEZE_DCO	(1 << 4)

 /**
  * struct clk_si570:
  * @hw:	Clock hw struct
  * @regmap:	Device's regmap
  * @div_offset:	Rgister offset for dividers
  * @max_freq:	Maximum frequency for this device
  * @fxtal:	Factory xtal frequency
  * @n1:		Clock divider N1
  * @hs_div:	Clock divider HSDIV
  * @rfreq:	Clock multiplier RFREQ
  * @frequency:	Current output frequency
  * @i2c_client:	I2C client pointer
  */
 struct clk_si570 {
 	struct clk_hw hw;
 	struct regmap *regmap;
 	unsigned int div_offset;
 	u64 max_freq;
 	u64 fxtal;
 	unsigned int n1;
 	unsigned int hs_div;
 	u64 rfreq;
 	u64 frequency;
 	struct i2c_client *i2c_client;
 };
 #define to_clk_si570(_hw)	container_of(_hw, struct clk_si570, hw)

 enum clk_si570_variant {
 	si57x,
 	si59x
 };

 /**
  * si570_get_divs() - Read clock dividers from HW
  * @data:	Pointer to struct clk_si570
  * @rfreq:	Fractional multiplier (output)
  * @n1:		Divider N1 (output)
  * @hs_div:	Divider HSDIV (output)
  * Returns 0 on success, negative errno otherwise.
  *
  * Retrieve clock dividers and multipliers from the HW.
  */
 static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
 		unsigned int *n1, unsigned int *hs_div)
 {
 	int err;
 	u8 reg[6];
 	u64 tmp;

 	err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
 			reg, ARRAY_SIZE(reg));
 	if (err)
 		return err;

 	*hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
 	*n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
 	/* Handle invalid cases */
 	if (*n1 > 1)
 		*n1 &= ~1;

 	tmp = reg[1] & RFREQ_37_32_MASK;
 	tmp = (tmp << 8) + reg[2];
 	tmp = (tmp << 8) + reg[3];
 	tmp = (tmp << 8) + reg[4];
 	tmp = (tmp << 8) + reg[5];
 	*rfreq = tmp;

 	return 0;
 }

 /**
  * si570_get_defaults() - Get default values
  * @data:	Driver data structure
  * @fout:	Factory frequency output
  * Returns 0 on success, negative errno otherwise.
  */
 static int si570_get_defaults(struct clk_si570 *data, u64 fout)
 {
 	int err;
 	u64 fdco;

 	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);

 	err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
 	if (err)
 		return err;

 	/*
 	 * Accept optional precision loss to avoid arithmetic overflows.
 	 * Acceptable per Silicon Labs Application Note AN334.
 	 */
 	fdco = fout * data->n1 * data->hs_div;
 	if (fdco >= (1LL << 36))
 		data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
 	else
 		data->fxtal = div64_u64(fdco << 28, data->rfreq);

 	data->frequency = fout;

 	return 0;
 }

 /**
  * si570_update_rfreq() - Update clock multiplier
  * @data:	Driver data structure
  * Passes on regmap_bulk_write() return value.
  */
 static int si570_update_rfreq(struct clk_si570 *data)
 {
 	u8 reg[5];

 	reg[0] = ((data->n1 - 1) << 6) |
 		((data->rfreq >> 32) & RFREQ_37_32_MASK);
 	reg[1] = (data->rfreq >> 24) & 0xff;
 	reg[2] = (data->rfreq >> 16) & 0xff;
 	reg[3] = (data->rfreq >> 8) & 0xff;
 	reg[4] = data->rfreq & 0xff;

 	return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
 			data->div_offset, reg, ARRAY_SIZE(reg));
 }

 /**
  * si570_calc_divs() - Caluclate clock dividers
  * @frequency:	Target frequency
  * @data:	Driver data structure
  * @out_rfreq:	RFREG fractional multiplier (output)
  * @out_n1:	Clock divider N1 (output)
  * @out_hs_div:	Clock divider HSDIV (output)
  * Returns 0 on success, negative errno otherwise.
  *
  * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
  * (@out_rfreq) for a given target @frequency.
  */
 static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
 		u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
 {
 	int i;
 	unsigned int n1, hs_div;
 	u64 fdco, best_fdco = ULLONG_MAX;
 	static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };

 	for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
 		hs_div = si570_hs_div_values[i];
 		/* Calculate lowest possible value for n1 */
 		n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
 		if (!n1 || (n1 & 1))
 			n1++;
 		while (n1 <= 128) {
 			fdco = (u64)frequency * (u64)hs_div * (u64)n1;
 			if (fdco > FDCO_MAX)
 				break;
 			if (fdco >= FDCO_MIN && fdco < best_fdco) {
 				*out_n1 = n1;
 				*out_hs_div = hs_div;
 				*out_rfreq = div64_u64(fdco << 28, data->fxtal);
 				best_fdco = fdco;
 			}
 			n1 += (n1 == 1 ? 1 : 2);
 		}
 	}

 	if (best_fdco == ULLONG_MAX)
 		return -EINVAL;

 	return 0;
 }

 static unsigned long si570_recalc_rate(struct clk_hw *hw,
 		unsigned long parent_rate)
 {
 	int err;
 	u64 rfreq, rate;
 	unsigned int n1, hs_div;
 	struct clk_si570 *data = to_clk_si570(hw);

 	err = si570_get_divs(data, &rfreq, &n1, &hs_div);
 	if (err) {
 		dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
 		return data->frequency;
 	}

 	rfreq = div_u64(rfreq, hs_div * n1);
 	rate = (data->fxtal * rfreq) >> 28;

 	return rate;
 }

 static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
 		unsigned long *parent_rate)
 {
 	int err;
 	u64 rfreq;
 	unsigned int n1, hs_div;
 	struct clk_si570 *data = to_clk_si570(hw);

 	if (!rate)
 		return 0;

 	if (div64_u64(abs(rate - data->frequency) * 10000LL,
 				data->frequency) < 35) {
 		rfreq = div64_u64((data->rfreq * rate) +
 				div64_u64(data->frequency, 2), data->frequency);
 		n1 = data->n1;
 		hs_div = data->hs_div;

 	} else {
 		err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
 		if (err) {
 			dev_err(&data->i2c_client->dev,
 					"unable to round rate\n");
 			return 0;
 		}
 	}

 	return rate;
 }

 /**
  * si570_set_frequency() - Adjust output frequency
  * @data:	Driver data structure
  * @frequency:	Target frequency
  * Returns 0 on success.
  *
  * Update output frequency for big frequency changes (> 3,500 ppm).
  */
 static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
 {
 	int err;

 	err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
 			&data->hs_div);
 	if (err)
 		return err;

 	/*
 	 * The DCO reg should be accessed with a read-modify-write operation
 	 * per AN334
 	 */
 	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
 	regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
 			((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
 			(((data->n1 - 1) >> 2) & N1_6_2_MASK));
 	si570_update_rfreq(data);
 	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
 	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);

 	/* Applying a new frequency can take up to 10ms */
 	usleep_range(10000, 12000);

 	return 0;
 }

 /**
  * si570_set_frequency_small() - Adjust output frequency
  * @data:	Driver data structure
  * @frequency:	Target frequency
  * Returns 0 on success.
  *
  * Update output frequency for small frequency changes (< 3,500 ppm).
  */
 static int si570_set_frequency_small(struct clk_si570 *data,
 				     unsigned long frequency)
 {
 	/*
 	 * This is a re-implementation of DIV_ROUND_CLOSEST
 	 * using the div64_u64 function lieu of letting the compiler
 	 * insert EABI calls
 	 */
 	data->rfreq = div64_u64((data->rfreq * frequency) +
 			div_u64(data->frequency, 2), data->frequency);
 	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
 	si570_update_rfreq(data);
 	regmap_write(data->regmap, SI570_REG_CONTROL, 0);

 	/* Applying a new frequency (small change) can take up to 100us */
 	usleep_range(100, 200);

 	return 0;
 }

 static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
 		unsigned long parent_rate)
 {
 	struct clk_si570 *data = to_clk_si570(hw);
 	struct i2c_client *client = data->i2c_client;
 	int err;

 	if (rate < SI570_MIN_FREQ || rate > data->max_freq) {
 		dev_err(&client->dev,
 			"requested frequency %lu Hz is out of range\n", rate);
 		return -EINVAL;
 	}

 	if (div64_u64(abs(rate - data->frequency) * 10000LL,
 				data->frequency) < 35)
 		err = si570_set_frequency_small(data, rate);
 	else
 		err = si570_set_frequency(data, rate);

 	if (err)
 		return err;

 	data->frequency = rate;

 	return 0;
 }

 static const struct clk_ops si570_clk_ops = {
 	.recalc_rate = si570_recalc_rate,
 	.round_rate = si570_round_rate,
 	.set_rate = si570_set_rate,
 };

 static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case SI570_REG_CONTROL:
 		return true;
 	default:
 		return false;
 	}
 }

 static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
 	case SI570_REG_CONTROL:
 	case SI570_REG_FREEZE_DCO:
 		return true;
 	default:
 		return false;
 	}
 }

 static const struct regmap_config si570_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.cache_type = REGCACHE_RBTREE,
 	.max_register = 137,
 	.writeable_reg = si570_regmap_is_writeable,
 	.volatile_reg = si570_regmap_is_volatile,
 };

 static int si570_probe(struct i2c_client *client,
 		const struct i2c_device_id *id)
 {
 	struct clk_si570 *data;
 	struct clk_init_data init;
 	struct clk *clk;
 	u32 initial_fout, factory_fout, stability;
 	int err;
 	enum clk_si570_variant variant = id->driver_data;

 	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;

 	init.ops = &si570_clk_ops;
 	init.flags = CLK_IS_ROOT;
 	init.num_parents = 0;
 	data->hw.init = &init;
 	data->i2c_client = client;

 	if (variant == si57x) {
 		err = of_property_read_u32(client->dev.of_node,
 				"temperature-stability", &stability);
 		if (err) {
 			dev_err(&client->dev,
 				  "'temperature-stability' property missing\n");
 			return err;
 		}
 		/* adjust register offsets for 7ppm devices */
 		if (stability == 7)
 			data->div_offset = SI570_DIV_OFFSET_7PPM;

 		data->max_freq = SI570_MAX_FREQ;
 	} else {
 		data->max_freq = SI598_MAX_FREQ;
 	}

 	if (of_property_read_string(client->dev.of_node, "clock-output-names",
 			&init.name))
 		init.name = client->dev.of_node->name;

 	err = of_property_read_u32(client->dev.of_node, "factory-fout",
 			&factory_fout);
 	if (err) {
 		dev_err(&client->dev, "'factory-fout' property missing\n");
 		return err;
 	}

 	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
 	if (IS_ERR(data->regmap)) {
 		dev_err(&client->dev, "failed to allocate register map\n");
 		return PTR_ERR(data->regmap);
 	}

 	i2c_set_clientdata(client, data);
 	err = si570_get_defaults(data, factory_fout);
 	if (err)
 		return err;

 	clk = devm_clk_register(&client->dev, &data->hw);
 	if (IS_ERR(clk)) {
 		dev_err(&client->dev, "clock registration failed\n");
 		return PTR_ERR(clk);
 	}
 	err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
 			clk);
 	if (err) {
 		dev_err(&client->dev, "unable to add clk provider\n");
 		return err;
 	}

 	/* Read the requested initial output frequency from device tree */
 	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
 				&initial_fout)) {
 		err = clk_set_rate(clk, initial_fout);
 		if (err) {
 			of_clk_del_provider(client->dev.of_node);
 			return err;
 		}
 	}

 	/* Display a message indicating that we've successfully registered */
 	dev_info(&client->dev, "registered, current frequency %llu Hz\n",
 			data->frequency);

 	return 0;
 }

 static int si570_remove(struct i2c_client *client)
 {
 	of_clk_del_provider(client->dev.of_node);
 	return 0;
 }

 static const struct i2c_device_id si570_id[] = {
 	{ "si570", si57x },
 	{ "si571", si57x },
 	{ "si598", si59x },
 	{ "si599", si59x },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, si570_id);

 static const struct of_device_id clk_si570_of_match[] = {
 	{ .compatible = "silabs,si570" },
 	{ .compatible = "silabs,si571" },
 	{ .compatible = "silabs,si598" },
 	{ .compatible = "silabs,si599" },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, clk_si570_of_match);

 static struct i2c_driver si570_driver = {
 	.driver = {
 		.name = "si570",
 		.of_match_table = clk_si570_of_match,
 	},
 	.probe		= si570_probe,
 	.remove		= si570_remove,
 	.id_table	= si570_id,
 };
 module_i2c_driver(si570_driver);

 MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
 MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
 MODULE_DESCRIPTION("Si570 driver");
 MODULE_LICENSE("GPL");
	/*
	* Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
	*
	* Copyright (C) 2010, 2011 Ericsson AB.
	* Copyright (C) 2011 Guenter Roeck.
	* Copyright (C) 2011 - 2013 Xilinx Inc.
	*
	* Author: Guenter Roeck <guenter.roeck@ericsson.com>
	* Sören Brinkmann <soren.brinkmann@xilinx.com>
	*
	* 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 <linux/clk-provider.h>
	#include <linux/delay.h>
	#include <linux/module.h>
	#include <linux/i2c.h>
	#include <linux/regmap.h>
	#include <linux/slab.h>

	/* Si570 registers */
	#define SI570_REG_HS_N1 7
	#define SI570_REG_N1_RFREQ0 8
	#define SI570_REG_RFREQ1 9
	#define SI570_REG_RFREQ2 10
	#define SI570_REG_RFREQ3 11
	#define SI570_REG_RFREQ4 12
	#define SI570_REG_CONTROL 135
	#define SI570_REG_FREEZE_DCO 137
	#define SI570_DIV_OFFSET_7PPM 6

	#define HS_DIV_SHIFT 5
	#define HS_DIV_MASK 0xe0
	#define HS_DIV_OFFSET 4
	#define N1_6_2_MASK 0x1f
	#define N1_1_0_MASK 0xc0
	#define RFREQ_37_32_MASK 0x3f

	#define SI570_MIN_FREQ 10000000L
	#define SI570_MAX_FREQ 1417500000L
	#define SI598_MAX_FREQ 525000000L

	#define FDCO_MIN 4850000000LL
	#define FDCO_MAX 5670000000LL

	#define SI570_CNTRL_RECALL (1 << 0)
	#define SI570_CNTRL_FREEZE_M (1 << 5)
	#define SI570_CNTRL_NEWFREQ (1 << 6)

	#define SI570_FREEZE_DCO (1 << 4)

	/**
	* struct clk_si570:
	* @hw: Clock hw struct
	* @regmap: Device's regmap
	* @div_offset: Rgister offset for dividers
	* @max_freq: Maximum frequency for this device
	* @fxtal: Factory xtal frequency
	* @n1: Clock divider N1
	* @hs_div: Clock divider HSDIV
	* @rfreq: Clock multiplier RFREQ
	* @frequency: Current output frequency
	* @i2c_client: I2C client pointer
	*/
	struct clk_si570 {
	struct clk_hw hw;
	struct regmap *regmap;
	unsigned int div_offset;
	u64 max_freq;
	u64 fxtal;
	unsigned int n1;
	unsigned int hs_div;
	u64 rfreq;
	u64 frequency;
	struct i2c_client *i2c_client;
	};
	#define to_clk_si570(_hw) container_of(_hw, struct clk_si570, hw)

	enum clk_si570_variant {
	si57x,
	si59x
	};

	/**
	* si570_get_divs() - Read clock dividers from HW
	* @data: Pointer to struct clk_si570
	* @rfreq: Fractional multiplier (output)
	* @n1: Divider N1 (output)
	* @hs_div: Divider HSDIV (output)
	* Returns 0 on success, negative errno otherwise.
	*
	* Retrieve clock dividers and multipliers from the HW.
	*/
	static int si570_get_divs(struct clk_si570 data, u64 rfreq,
	unsigned int n1, unsigned int hs_div)
	{
	int err;
	u8 reg[6];
	u64 tmp;

	err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
	reg, ARRAY_SIZE(reg));
	if (err)
	return err;

	*hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
	*n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
	/* Handle invalid cases */
	if (*n1 > 1)
	*n1 &= ~1;

	tmp = reg[1] & RFREQ_37_32_MASK;
	tmp = (tmp << 8) + reg[2];
	tmp = (tmp << 8) + reg[3];
	tmp = (tmp << 8) + reg[4];
	tmp = (tmp << 8) + reg[5];
	*rfreq = tmp;

	return 0;
	}

	/**
	* si570_get_defaults() - Get default values
	* @data: Driver data structure
	* @fout: Factory frequency output
	* Returns 0 on success, negative errno otherwise.
	*/
	static int si570_get_defaults(struct clk_si570 *data, u64 fout)
	{
	int err;
	u64 fdco;

	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);

	err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
	if (err)
	return err;

	/*
	* Accept optional precision loss to avoid arithmetic overflows.
	* Acceptable per Silicon Labs Application Note AN334.
	*/
	fdco = fout * data->n1 * data->hs_div;
	if (fdco >= (1LL << 36))
	data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
	else
	data->fxtal = div64_u64(fdco << 28, data->rfreq);

	data->frequency = fout;

	return 0;
	}

	/**
	* si570_update_rfreq() - Update clock multiplier
	* @data: Driver data structure
	* Passes on regmap_bulk_write() return value.
	*/
	static int si570_update_rfreq(struct clk_si570 *data)
	{
	u8 reg[5];

	reg[0] = ((data->n1 - 1) << 6) \|
	((data->rfreq >> 32) & RFREQ_37_32_MASK);
	reg[1] = (data->rfreq >> 24) & 0xff;
	reg[2] = (data->rfreq >> 16) & 0xff;
	reg[3] = (data->rfreq >> 8) & 0xff;
	reg[4] = data->rfreq & 0xff;

	return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
	data->div_offset, reg, ARRAY_SIZE(reg));
	}

	/**
	* si570_calc_divs() - Caluclate clock dividers
	* @frequency: Target frequency
	* @data: Driver data structure
	* @out_rfreq: RFREG fractional multiplier (output)
	* @out_n1: Clock divider N1 (output)
	* @out_hs_div: Clock divider HSDIV (output)
	* Returns 0 on success, negative errno otherwise.
	*
	* Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
	* (@out_rfreq) for a given target @frequency.
	*/
	static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
	u64 out_rfreq, unsigned int out_n1, unsigned int *out_hs_div)
	{
	int i;
	unsigned int n1, hs_div;
	u64 fdco, best_fdco = ULLONG_MAX;
	static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };

	for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
	hs_div = si570_hs_div_values[i];
	/* Calculate lowest possible value for n1 */
	n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
	if (!n1 \|\| (n1 & 1))
	n1++;
	while (n1 <= 128) {
	fdco = (u64)frequency * (u64)hs_div * (u64)n1;
	if (fdco > FDCO_MAX)
	break;
	if (fdco >= FDCO_MIN && fdco < best_fdco) {
	*out_n1 = n1;
	*out_hs_div = hs_div;
	*out_rfreq = div64_u64(fdco << 28, data->fxtal);
	best_fdco = fdco;
	}
	n1 += (n1 == 1 ? 1 : 2);
	}
	}

	if (best_fdco == ULLONG_MAX)
	return -EINVAL;

	return 0;
	}

	static unsigned long si570_recalc_rate(struct clk_hw *hw,
	unsigned long parent_rate)
	{
	int err;
	u64 rfreq, rate;
	unsigned int n1, hs_div;
	struct clk_si570 *data = to_clk_si570(hw);

	err = si570_get_divs(data, &rfreq, &n1, &hs_div);
	if (err) {
	dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
	return data->frequency;
	}

	rfreq = div_u64(rfreq, hs_div * n1);
	rate = (data->fxtal * rfreq) >> 28;

	return rate;
	}

	static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
	unsigned long *parent_rate)
	{
	int err;
	u64 rfreq;
	unsigned int n1, hs_div;
	struct clk_si570 *data = to_clk_si570(hw);

	if (!rate)
	return 0;

	if (div64_u64(abs(rate - data->frequency) * 10000LL,
	data->frequency) < 35) {
	rfreq = div64_u64((data->rfreq * rate) +
	div64_u64(data->frequency, 2), data->frequency);
	n1 = data->n1;
	hs_div = data->hs_div;

	} else {
	err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
	if (err) {
	dev_err(&data->i2c_client->dev,
	"unable to round rate\n");
	return 0;
	}
	}

	return rate;
	}

	/**
	* si570_set_frequency() - Adjust output frequency
	* @data: Driver data structure
	* @frequency: Target frequency
	* Returns 0 on success.
	*
	* Update output frequency for big frequency changes (> 3,500 ppm).
	*/
	static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
	{
	int err;

	err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
	&data->hs_div);
	if (err)
	return err;

	/*
	* The DCO reg should be accessed with a read-modify-write operation
	* per AN334
	*/
	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
	regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
	((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) \|
	(((data->n1 - 1) >> 2) & N1_6_2_MASK));
	si570_update_rfreq(data);
	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);

	/* Applying a new frequency can take up to 10ms */
	usleep_range(10000, 12000);

	return 0;
	}

	/**
	* si570_set_frequency_small() - Adjust output frequency
	* @data: Driver data structure
	* @frequency: Target frequency
	* Returns 0 on success.
	*
	* Update output frequency for small frequency changes (< 3,500 ppm).
	*/
	static int si570_set_frequency_small(struct clk_si570 *data,
	unsigned long frequency)
	{
	/*
	* This is a re-implementation of DIV_ROUND_CLOSEST
	* using the div64_u64 function lieu of letting the compiler
	* insert EABI calls
	*/
	data->rfreq = div64_u64((data->rfreq * frequency) +
	div_u64(data->frequency, 2), data->frequency);
	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
	si570_update_rfreq(data);
	regmap_write(data->regmap, SI570_REG_CONTROL, 0);

	/* Applying a new frequency (small change) can take up to 100us */
	usleep_range(100, 200);

	return 0;
	}

	static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
	unsigned long parent_rate)
	{
	struct clk_si570 *data = to_clk_si570(hw);
	struct i2c_client *client = data->i2c_client;
	int err;

	if (rate < SI570_MIN_FREQ \|\| rate > data->max_freq) {
	dev_err(&client->dev,
	"requested frequency %lu Hz is out of range\n", rate);
	return -EINVAL;
	}

	if (div64_u64(abs(rate - data->frequency) * 10000LL,
	data->frequency) < 35)
	err = si570_set_frequency_small(data, rate);
	else
	err = si570_set_frequency(data, rate);

	if (err)
	return err;

	data->frequency = rate;

	return 0;
	}

	static const struct clk_ops si570_clk_ops = {
	.recalc_rate = si570_recalc_rate,
	.round_rate = si570_round_rate,
	.set_rate = si570_set_rate,
	};

	static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
	{
	switch (reg) {
	case SI570_REG_CONTROL:
	return true;
	default:
	return false;
	}
	}

	static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
	{
	switch (reg) {
	case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
	case SI570_REG_CONTROL:
	case SI570_REG_FREEZE_DCO:
	return true;
	default:
	return false;
	}
	}

	static const struct regmap_config si570_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.cache_type = REGCACHE_RBTREE,
	.max_register = 137,
	.writeable_reg = si570_regmap_is_writeable,
	.volatile_reg = si570_regmap_is_volatile,
	};

	static int si570_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct clk_si570 *data;
	struct clk_init_data init;
	struct clk *clk;
	u32 initial_fout, factory_fout, stability;
	int err;
	enum clk_si570_variant variant = id->driver_data;

	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
	if (!data)
	return -ENOMEM;

	init.ops = &si570_clk_ops;
	init.flags = CLK_IS_ROOT;
	init.num_parents = 0;
	data->hw.init = &init;
	data->i2c_client = client;

	if (variant == si57x) {
	err = of_property_read_u32(client->dev.of_node,
	"temperature-stability", &stability);
	if (err) {
	dev_err(&client->dev,
	"'temperature-stability' property missing\n");
	return err;
	}
	/* adjust register offsets for 7ppm devices */
	if (stability == 7)
	data->div_offset = SI570_DIV_OFFSET_7PPM;

	data->max_freq = SI570_MAX_FREQ;
	} else {
	data->max_freq = SI598_MAX_FREQ;
	}

	if (of_property_read_string(client->dev.of_node, "clock-output-names",
	&init.name))
	init.name = client->dev.of_node->name;

	err = of_property_read_u32(client->dev.of_node, "factory-fout",
	&factory_fout);
	if (err) {
	dev_err(&client->dev, "'factory-fout' property missing\n");
	return err;
	}

	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
	if (IS_ERR(data->regmap)) {
	dev_err(&client->dev, "failed to allocate register map\n");
	return PTR_ERR(data->regmap);
	}

	i2c_set_clientdata(client, data);
	err = si570_get_defaults(data, factory_fout);
	if (err)
	return err;

	clk = devm_clk_register(&client->dev, &data->hw);
	if (IS_ERR(clk)) {
	dev_err(&client->dev, "clock registration failed\n");
	return PTR_ERR(clk);
	}
	err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
	clk);
	if (err) {
	dev_err(&client->dev, "unable to add clk provider\n");
	return err;
	}

	/* Read the requested initial output frequency from device tree */
	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
	&initial_fout)) {
	err = clk_set_rate(clk, initial_fout);
	if (err) {
	of_clk_del_provider(client->dev.of_node);
	return err;
	}
	}

	/* Display a message indicating that we've successfully registered */
	dev_info(&client->dev, "registered, current frequency %llu Hz\n",
	data->frequency);

	return 0;
	}

	static int si570_remove(struct i2c_client *client)
	{
	of_clk_del_provider(client->dev.of_node);
	return 0;
	}

	static const struct i2c_device_id si570_id[] = {
	{ "si570", si57x },
	{ "si571", si57x },
	{ "si598", si59x },
	{ "si599", si59x },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, si570_id);

	static const struct of_device_id clk_si570_of_match[] = {
	{ .compatible = "silabs,si570" },
	{ .compatible = "silabs,si571" },
	{ .compatible = "silabs,si598" },
	{ .compatible = "silabs,si599" },
	{ },
	};
	MODULE_DEVICE_TABLE(of, clk_si570_of_match);

	static struct i2c_driver si570_driver = {
	.driver = {
	.name = "si570",
	.of_match_table = clk_si570_of_match,
	},
	.probe = si570_probe,
	.remove = si570_remove,
	.id_table = si570_id,
	};
	module_i2c_driver(si570_driver);

	MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
	MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
	MODULE_DESCRIPTION("Si570 driver");
	MODULE_LICENSE("GPL");