1/*
  2 * Driver for Silicon Labs Si514 Programmable Oscillator
  3 *
  4 * Copyright (C) 2015 Topic Embedded Products
  5 *
  6 * Author: Mike Looijmans <mike.looijmans@topic.nl>
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License as published by
 10 * the Free Software Foundation; either version 2 of the License, or
 11 * (at your option) any later version.
 12 *
 13 * This program is distributed in the hope that it will be useful,
 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 16 * GNU General Public License for more details.
 17 */
 18
 19#include <linux/clk-provider.h>
 20#include <linux/delay.h>
 21#include <linux/module.h>
 22#include <linux/i2c.h>
 23#include <linux/regmap.h>
 24#include <linux/slab.h>
 25
 26/* I2C registers */
 27#define SI514_REG_LP		0
 28#define SI514_REG_M_FRAC1	5
 29#define SI514_REG_M_FRAC2	6
 30#define SI514_REG_M_FRAC3	7
 31#define SI514_REG_M_INT_FRAC	8
 32#define SI514_REG_M_INT		9
 33#define SI514_REG_HS_DIV	10
 34#define SI514_REG_LS_HS_DIV	11
 35#define SI514_REG_OE_STATE	14
 36#define SI514_REG_RESET		128
 37#define SI514_REG_CONTROL	132
 38
 39/* Register values */
 40#define SI514_RESET_RST		BIT(7)
 41
 42#define SI514_CONTROL_FCAL	BIT(0)
 43#define SI514_CONTROL_OE	BIT(2)
 44
 45#define SI514_MIN_FREQ	    100000U
 46#define SI514_MAX_FREQ	 250000000U
 47
 48#define FXO		  31980000U
 49
 50#define FVCO_MIN	2080000000U
 51#define FVCO_MAX	2500000000U
 52
 53#define HS_DIV_MAX	1022
 54
 55struct clk_si514 {
 56	struct clk_hw hw;
 57	struct regmap *regmap;
 58	struct i2c_client *i2c_client;
 59};
 60#define to_clk_si514(_hw)	container_of(_hw, struct clk_si514, hw)
 61
 62/* Multiplier/divider settings */
 63struct clk_si514_muldiv {
 64	u32 m_frac;  /* 29-bit Fractional part of multiplier M */
 65	u8 m_int; /* Integer part of multiplier M, 65..78 */
 66	u8 ls_div_bits; /* 2nd divider, as 2^x */
 67	u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
 68};
 69
 70/* Enables or disables the output driver */
 71static int si514_enable_output(struct clk_si514 *data, bool enable)
 72{
 73	return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
 74		SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
 75}
 76
 77/* Retrieve clock multiplier and dividers from hardware */
 78static int si514_get_muldiv(struct clk_si514 *data,
 79	struct clk_si514_muldiv *settings)
 80{
 81	int err;
 82	u8 reg[7];
 83
 84	err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
 85			reg, ARRAY_SIZE(reg));
 86	if (err)
 87		return err;
 88
 89	settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
 90			   (reg[3] & 0x1F) << 24;
 91	settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
 92	settings->ls_div_bits = (reg[6] >> 4) & 0x07;
 93	settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
 94	return 0;
 95}
 96
 97static int si514_set_muldiv(struct clk_si514 *data,
 98	struct clk_si514_muldiv *settings)
 99{
100	u8 lp;
101	u8 reg[7];
102	int err;
103
104	/* Calculate LP1/LP2 according to table 13 in the datasheet */
105	/* 65.259980246 */
106	if (settings->m_int < 65 ||
107		(settings->m_int == 65 && settings->m_frac <= 139575831))
108		lp = 0x22;
109	/* 67.859763463 */
110	else if (settings->m_int < 67 ||
111		(settings->m_int == 67 && settings->m_frac <= 461581994))
112		lp = 0x23;
113	/* 72.937624981 */
114	else if (settings->m_int < 72 ||
115		(settings->m_int == 72 && settings->m_frac <= 503383578))
116		lp = 0x33;
117	/* 75.843265046 */
118	else if (settings->m_int < 75 ||
119		(settings->m_int == 75 && settings->m_frac <= 452724474))
120		lp = 0x34;
121	else
122		lp = 0x44;
123
124	err = regmap_write(data->regmap, SI514_REG_LP, lp);
125	if (err < 0)
126		return err;
127
128	reg[0] = settings->m_frac;
129	reg[1] = settings->m_frac >> 8;
130	reg[2] = settings->m_frac >> 16;
131	reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
132	reg[4] = settings->m_int >> 3;
133	reg[5] = settings->hs_div;
134	reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
135
136	err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
137	if (err < 0)
138		return err;
139	/*
140	 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
141	 * must be written last
142	 */
143	return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
144}
145
146/* Calculate divider settings for a given frequency */
147static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
148	unsigned long frequency)
149{
150	u64 m;
151	u32 ls_freq;
152	u32 tmp;
153	u8 res;
154
155	if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
156		return -EINVAL;
157
158	/* Determine the minimum value of LS_DIV and resulting target freq. */
159	ls_freq = frequency;
160	if (frequency >= (FVCO_MIN / HS_DIV_MAX))
161		settings->ls_div_bits = 0;
162	else {
163		res = 1;
164		tmp = 2 * HS_DIV_MAX;
165		while (tmp <= (HS_DIV_MAX * 32)) {
166			if ((frequency * tmp) >= FVCO_MIN)
167				break;
168			++res;
169			tmp <<= 1;
170		}
171		settings->ls_div_bits = res;
172		ls_freq = frequency << res;
173	}
174
175	/* Determine minimum HS_DIV, round up to even number */
176	settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
177
178	/* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
179	m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
180	do_div(m, FXO);
181	settings->m_frac = (u32)m & (BIT(29) - 1);
182	settings->m_int = (u32)(m >> 29);
183
184	return 0;
185}
186
187/* Calculate resulting frequency given the register settings */
188static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
189{
190	u64 m = settings->m_frac | ((u64)settings->m_int << 29);
191	u32 d = settings->hs_div * BIT(settings->ls_div_bits);
192
193	return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
194}
195
196static unsigned long si514_recalc_rate(struct clk_hw *hw,
197		unsigned long parent_rate)
198{
199	struct clk_si514 *data = to_clk_si514(hw);
200	struct clk_si514_muldiv settings;
201	int err;
202
203	err = si514_get_muldiv(data, &settings);
204	if (err) {
205		dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
206		return 0;
207	}
208
209	return si514_calc_rate(&settings);
210}
211
212static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
213		unsigned long *parent_rate)
214{
215	struct clk_si514_muldiv settings;
216	int err;
217
218	if (!rate)
219		return 0;
220
221	err = si514_calc_muldiv(&settings, rate);
222	if (err)
223		return err;
224
225	return si514_calc_rate(&settings);
226}
227
228/*
229 * Update output frequency for big frequency changes (> 1000 ppm).
230 * The chip supports <1000ppm changes "on the fly", we haven't implemented
231 * that here.
232 */
233static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
234		unsigned long parent_rate)
235{
236	struct clk_si514 *data = to_clk_si514(hw);
237	struct clk_si514_muldiv settings;
238	int err;
239
240	err = si514_calc_muldiv(&settings, rate);
241	if (err)
242		return err;
243
244	si514_enable_output(data, false);
245
246	err = si514_set_muldiv(data, &settings);
247	if (err < 0)
248		return err; /* Undefined state now, best to leave disabled */
249
250	/* Trigger calibration */
251	err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
252	if (err < 0)
253		return err;
254
255	/* Applying a new frequency can take up to 10ms */
256	usleep_range(10000, 12000);
257
258	si514_enable_output(data, true);
259
260	return err;
261}
262
263static const struct clk_ops si514_clk_ops = {
264	.recalc_rate = si514_recalc_rate,
265	.round_rate = si514_round_rate,
266	.set_rate = si514_set_rate,
267};
268
269static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
270{
271	switch (reg) {
272	case SI514_REG_CONTROL:
273	case SI514_REG_RESET:
274		return true;
275	default:
276		return false;
277	}
278}
279
280static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
281{
282	switch (reg) {
283	case SI514_REG_LP:
284	case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
285	case SI514_REG_OE_STATE:
286	case SI514_REG_RESET:
287	case SI514_REG_CONTROL:
288		return true;
289	default:
290		return false;
291	}
292}
293
294static const struct regmap_config si514_regmap_config = {
295	.reg_bits = 8,
296	.val_bits = 8,
297	.cache_type = REGCACHE_RBTREE,
298	.max_register = SI514_REG_CONTROL,
299	.writeable_reg = si514_regmap_is_writeable,
300	.volatile_reg = si514_regmap_is_volatile,
301};
302
303static int si514_probe(struct i2c_client *client,
304		const struct i2c_device_id *id)
305{
306	struct clk_si514 *data;
307	struct clk_init_data init;
308	int err;
309
310	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
311	if (!data)
312		return -ENOMEM;
313
314	init.ops = &si514_clk_ops;
315	init.flags = 0;
316	init.num_parents = 0;
317	data->hw.init = &init;
318	data->i2c_client = client;
319
320	if (of_property_read_string(client->dev.of_node, "clock-output-names",
321			&init.name))
322		init.name = client->dev.of_node->name;
323
324	data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
325	if (IS_ERR(data->regmap)) {
326		dev_err(&client->dev, "failed to allocate register map\n");
327		return PTR_ERR(data->regmap);
328	}
329
330	i2c_set_clientdata(client, data);
331
332	err = devm_clk_hw_register(&client->dev, &data->hw);
333	if (err) {
334		dev_err(&client->dev, "clock registration failed\n");
335		return err;
336	}
337	err = of_clk_add_hw_provider(client->dev.of_node, of_clk_hw_simple_get,
338				     &data->hw);
339	if (err) {
340		dev_err(&client->dev, "unable to add clk provider\n");
341		return err;
342	}
343
344	return 0;
345}
346
347static int si514_remove(struct i2c_client *client)
348{
349	of_clk_del_provider(client->dev.of_node);
350	return 0;
351}
352
353static const struct i2c_device_id si514_id[] = {
354	{ "si514", 0 },
355	{ }
356};
357MODULE_DEVICE_TABLE(i2c, si514_id);
358
359static const struct of_device_id clk_si514_of_match[] = {
360	{ .compatible = "silabs,si514" },
361	{ },
362};
363MODULE_DEVICE_TABLE(of, clk_si514_of_match);
364
365static struct i2c_driver si514_driver = {
366	.driver = {
367		.name = "si514",
368		.of_match_table = clk_si514_of_match,
369	},
370	.probe		= si514_probe,
371	.remove		= si514_remove,
372	.id_table	= si514_id,
373};
374module_i2c_driver(si514_driver);
375
376MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
377MODULE_DESCRIPTION("Si514 driver");
378MODULE_LICENSE("GPL");