clk-si514.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Driver for Silicon Labs Si514 Programmable Oscillator
  4 *
  5 * Copyright (C) 2015 Topic Embedded Products
  6 *
  7 * Author: Mike Looijmans <mike.looijmans@topic.nl>
  8 */
  9
 10#include <linux/clk-provider.h>
 11#include <linux/delay.h>
 12#include <linux/module.h>
 13#include <linux/i2c.h>
 14#include <linux/regmap.h>
 15#include <linux/slab.h>
 16
 17/* I2C registers */
 18#define SI514_REG_LP		0
 19#define SI514_REG_M_FRAC1	5
 20#define SI514_REG_M_FRAC2	6
 21#define SI514_REG_M_FRAC3	7
 22#define SI514_REG_M_INT_FRAC	8
 23#define SI514_REG_M_INT		9
 24#define SI514_REG_HS_DIV	10
 25#define SI514_REG_LS_HS_DIV	11
 26#define SI514_REG_OE_STATE	14
 27#define SI514_REG_RESET		128
 28#define SI514_REG_CONTROL	132
 29
 30/* Register values */
 31#define SI514_RESET_RST		BIT(7)
 32
 33#define SI514_CONTROL_FCAL	BIT(0)
 34#define SI514_CONTROL_OE	BIT(2)
 35
 36#define SI514_MIN_FREQ	    100000U
 37#define SI514_MAX_FREQ	 250000000U
 38
 39#define FXO		  31980000U
 40
 41#define FVCO_MIN	2080000000U
 42#define FVCO_MAX	2500000000U
 43
 44#define HS_DIV_MAX	1022
 45
 46struct clk_si514 {
 47	struct clk_hw hw;
 48	struct regmap *regmap;
 49	struct i2c_client *i2c_client;
 50};
 51#define to_clk_si514(_hw)	container_of(_hw, struct clk_si514, hw)
 52
 53/* Multiplier/divider settings */
 54struct clk_si514_muldiv {
 55	u32 m_frac;  /* 29-bit Fractional part of multiplier M */
 56	u8 m_int; /* Integer part of multiplier M, 65..78 */
 57	u8 ls_div_bits; /* 2nd divider, as 2^x */
 58	u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
 59};
 60
 61/* Enables or disables the output driver */
 62static int si514_enable_output(struct clk_si514 *data, bool enable)
 63{
 64	return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
 65		SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
 66}
 67
 68static int si514_prepare(struct clk_hw *hw)
 69{
 70	struct clk_si514 *data = to_clk_si514(hw);
 71
 72	return si514_enable_output(data, true);
 73}
 74
 75static void si514_unprepare(struct clk_hw *hw)
 76{
 77	struct clk_si514 *data = to_clk_si514(hw);
 78
 79	si514_enable_output(data, false);
 80}
 81
 82static int si514_is_prepared(struct clk_hw *hw)
 83{
 84	struct clk_si514 *data = to_clk_si514(hw);
 85	unsigned int val;
 86	int err;
 87
 88	err = regmap_read(data->regmap, SI514_REG_CONTROL, &val);
 89	if (err < 0)
 90		return err;
 91
 92	return !!(val & SI514_CONTROL_OE);
 93}
 94
 95/* Retrieve clock multiplier and dividers from hardware */
 96static int si514_get_muldiv(struct clk_si514 *data,
 97	struct clk_si514_muldiv *settings)
 98{
 99	int err;
100	u8 reg[7];
101
102	err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
103			reg, ARRAY_SIZE(reg));
104	if (err)
105		return err;
106
107	settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
108			   (reg[3] & 0x1F) << 24;
109	settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
110	settings->ls_div_bits = (reg[6] >> 4) & 0x07;
111	settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
112	return 0;
113}
114
115static int si514_set_muldiv(struct clk_si514 *data,
116	struct clk_si514_muldiv *settings)
117{
118	u8 lp;
119	u8 reg[7];
120	int err;
121
122	/* Calculate LP1/LP2 according to table 13 in the datasheet */
123	/* 65.259980246 */
124	if (settings->m_int < 65 ||
125		(settings->m_int == 65 && settings->m_frac <= 139575831))
126		lp = 0x22;
127	/* 67.859763463 */
128	else if (settings->m_int < 67 ||
129		(settings->m_int == 67 && settings->m_frac <= 461581994))
130		lp = 0x23;
131	/* 72.937624981 */
132	else if (settings->m_int < 72 ||
133		(settings->m_int == 72 && settings->m_frac <= 503383578))
134		lp = 0x33;
135	/* 75.843265046 */
136	else if (settings->m_int < 75 ||
137		(settings->m_int == 75 && settings->m_frac <= 452724474))
138		lp = 0x34;
139	else
140		lp = 0x44;
141
142	err = regmap_write(data->regmap, SI514_REG_LP, lp);
143	if (err < 0)
144		return err;
145
146	reg[0] = settings->m_frac;
147	reg[1] = settings->m_frac >> 8;
148	reg[2] = settings->m_frac >> 16;
149	reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
150	reg[4] = settings->m_int >> 3;
151	reg[5] = settings->hs_div;
152	reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
153
154	err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
155	if (err < 0)
156		return err;
157	/*
158	 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
159	 * must be written last
160	 */
161	return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
162}
163
164/* Calculate divider settings for a given frequency */
165static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
166	unsigned long frequency)
167{
168	u64 m;
169	u32 ls_freq;
170	u32 tmp;
171	u8 res;
172
173	if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
174		return -EINVAL;
175
176	/* Determine the minimum value of LS_DIV and resulting target freq. */
177	ls_freq = frequency;
178	if (frequency >= (FVCO_MIN / HS_DIV_MAX))
179		settings->ls_div_bits = 0;
180	else {
181		res = 1;
182		tmp = 2 * HS_DIV_MAX;
183		while (tmp <= (HS_DIV_MAX * 32)) {
184			if ((frequency * tmp) >= FVCO_MIN)
185				break;
186			++res;
187			tmp <<= 1;
188		}
189		settings->ls_div_bits = res;
190		ls_freq = frequency << res;
191	}
192
193	/* Determine minimum HS_DIV, round up to even number */
194	settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
195
196	/* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
197	m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
198	do_div(m, FXO);
199	settings->m_frac = (u32)m & (BIT(29) - 1);
200	settings->m_int = (u32)(m >> 29);
201
202	return 0;
203}
204
205/* Calculate resulting frequency given the register settings */
206static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
207{
208	u64 m = settings->m_frac | ((u64)settings->m_int << 29);
209	u32 d = settings->hs_div * BIT(settings->ls_div_bits);
210
211	return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
212}
213
214static unsigned long si514_recalc_rate(struct clk_hw *hw,
215		unsigned long parent_rate)
216{
217	struct clk_si514 *data = to_clk_si514(hw);
218	struct clk_si514_muldiv settings;
219	int err;
220
221	err = si514_get_muldiv(data, &settings);
222	if (err) {
223		dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
224		return 0;
225	}
226
227	return si514_calc_rate(&settings);
228}
229
230static int si514_determine_rate(struct clk_hw *hw,
231				struct clk_rate_request *req)
232{
233	struct clk_si514_muldiv settings;
234	int err;
235
236	if (!req->rate) {
237		req->rate = 0;
238
239		return 0;
240	}
241
242	err = si514_calc_muldiv(&settings, req->rate);
243	if (err) {
244		req->rate = err;
245
246		return 0;
247	}
248
249	req->rate = si514_calc_rate(&settings);
250
251	return 0;
252}
253
254/*
255 * Update output frequency for big frequency changes (> 1000 ppm).
256 * The chip supports <1000ppm changes "on the fly", we haven't implemented
257 * that here.
258 */
259static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
260		unsigned long parent_rate)
261{
262	struct clk_si514 *data = to_clk_si514(hw);
263	struct clk_si514_muldiv settings;
264	unsigned int old_oe_state;
265	int err;
266
267	err = si514_calc_muldiv(&settings, rate);
268	if (err)
269		return err;
270
271	err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
272	if (err)
273		return err;
274
275	si514_enable_output(data, false);
276
277	err = si514_set_muldiv(data, &settings);
278	if (err < 0)
279		return err; /* Undefined state now, best to leave disabled */
280
281	/* Trigger calibration */
282	err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
283	if (err < 0)
284		return err;
285
286	/* Applying a new frequency can take up to 10ms */
287	usleep_range(10000, 12000);
288
289	if (old_oe_state & SI514_CONTROL_OE)
290		si514_enable_output(data, true);
291
292	return err;
293}
294
295static const struct clk_ops si514_clk_ops = {
296	.prepare = si514_prepare,
297	.unprepare = si514_unprepare,
298	.is_prepared = si514_is_prepared,
299	.recalc_rate = si514_recalc_rate,
300	.determine_rate = si514_determine_rate,
301	.set_rate = si514_set_rate,
302};
303
304static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
305{
306	switch (reg) {
307	case SI514_REG_CONTROL:
308	case SI514_REG_RESET:
309		return true;
310	default:
311		return false;
312	}
313}
314
315static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
316{
317	switch (reg) {
318	case SI514_REG_LP:
319	case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
320	case SI514_REG_OE_STATE:
321	case SI514_REG_RESET:
322	case SI514_REG_CONTROL:
323		return true;
324	default:
325		return false;
326	}
327}
328
329static const struct regmap_config si514_regmap_config = {
330	.reg_bits = 8,
331	.val_bits = 8,
332	.cache_type = REGCACHE_MAPLE,
333	.max_register = SI514_REG_CONTROL,
334	.writeable_reg = si514_regmap_is_writeable,
335	.volatile_reg = si514_regmap_is_volatile,
336};
337
338static int si514_probe(struct i2c_client *client)
339{
340	struct clk_si514 *data;
341	struct clk_init_data init;
342	int err;
343
344	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
345	if (!data)
346		return -ENOMEM;
347
348	init.ops = &si514_clk_ops;
349	init.flags = 0;
350	init.num_parents = 0;
351	data->hw.init = &init;
352	data->i2c_client = client;
353
354	if (of_property_read_string(client->dev.of_node, "clock-output-names",
355			&init.name))
356		init.name = client->dev.of_node->name;
357
358	data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
359	if (IS_ERR(data->regmap)) {
360		dev_err(&client->dev, "failed to allocate register map\n");
361		return PTR_ERR(data->regmap);
362	}
363
364	i2c_set_clientdata(client, data);
365
366	err = devm_clk_hw_register(&client->dev, &data->hw);
367	if (err) {
368		dev_err(&client->dev, "clock registration failed\n");
369		return err;
370	}
371	err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
372					  &data->hw);
373	if (err) {
374		dev_err(&client->dev, "unable to add clk provider\n");
375		return err;
376	}
377
378	return 0;
379}
380
381static const struct i2c_device_id si514_id[] = {
382	{ "si514" },
383	{ }
384};
385MODULE_DEVICE_TABLE(i2c, si514_id);
386
387static const struct of_device_id clk_si514_of_match[] = {
388	{ .compatible = "silabs,si514" },
389	{ },
390};
391MODULE_DEVICE_TABLE(of, clk_si514_of_match);
392
393static struct i2c_driver si514_driver = {
394	.driver = {
395		.name = "si514",
396		.of_match_table = clk_si514_of_match,
397	},
398	.probe		= si514_probe,
399	.id_table	= si514_id,
400};
401module_i2c_driver(si514_driver);
402
403MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
404MODULE_DESCRIPTION("Si514 driver");
405MODULE_LICENSE("GPL");