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 long si514_round_rate(struct clk_hw *hw, unsigned long rate,
231		unsigned long *parent_rate)
232{
233	struct clk_si514_muldiv settings;
234	int err;
235
236	if (!rate)
237		return 0;
238
239	err = si514_calc_muldiv(&settings, rate);
240	if (err)
241		return err;
242
243	return si514_calc_rate(&settings);
244}
245
246/*
247 * Update output frequency for big frequency changes (> 1000 ppm).
248 * The chip supports <1000ppm changes "on the fly", we haven't implemented
249 * that here.
250 */
251static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
252		unsigned long parent_rate)
253{
254	struct clk_si514 *data = to_clk_si514(hw);
255	struct clk_si514_muldiv settings;
256	unsigned int old_oe_state;
257	int err;
258
259	err = si514_calc_muldiv(&settings, rate);
260	if (err)
261		return err;
262
263	err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
264	if (err)
265		return err;
266
267	si514_enable_output(data, false);
268
269	err = si514_set_muldiv(data, &settings);
270	if (err < 0)
271		return err; /* Undefined state now, best to leave disabled */
272
273	/* Trigger calibration */
274	err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
275	if (err < 0)
276		return err;
277
278	/* Applying a new frequency can take up to 10ms */
279	usleep_range(10000, 12000);
280
281	if (old_oe_state & SI514_CONTROL_OE)
282		si514_enable_output(data, true);
283
284	return err;
285}
286
287static const struct clk_ops si514_clk_ops = {
288	.prepare = si514_prepare,
289	.unprepare = si514_unprepare,
290	.is_prepared = si514_is_prepared,
291	.recalc_rate = si514_recalc_rate,
292	.round_rate = si514_round_rate,
293	.set_rate = si514_set_rate,
294};
295
296static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
297{
298	switch (reg) {
299	case SI514_REG_CONTROL:
300	case SI514_REG_RESET:
301		return true;
302	default:
303		return false;
304	}
305}
306
307static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
308{
309	switch (reg) {
310	case SI514_REG_LP:
311	case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
312	case SI514_REG_OE_STATE:
313	case SI514_REG_RESET:
314	case SI514_REG_CONTROL:
315		return true;
316	default:
317		return false;
318	}
319}
320
321static const struct regmap_config si514_regmap_config = {
322	.reg_bits = 8,
323	.val_bits = 8,
324	.cache_type = REGCACHE_MAPLE,
325	.max_register = SI514_REG_CONTROL,
326	.writeable_reg = si514_regmap_is_writeable,
327	.volatile_reg = si514_regmap_is_volatile,
328};
329
330static int si514_probe(struct i2c_client *client)
331{
332	struct clk_si514 *data;
333	struct clk_init_data init;
334	int err;
335
336	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
337	if (!data)
338		return -ENOMEM;
339
340	init.ops = &si514_clk_ops;
341	init.flags = 0;
342	init.num_parents = 0;
343	data->hw.init = &init;
344	data->i2c_client = client;
345
346	if (of_property_read_string(client->dev.of_node, "clock-output-names",
347			&init.name))
348		init.name = client->dev.of_node->name;
349
350	data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
351	if (IS_ERR(data->regmap)) {
352		dev_err(&client->dev, "failed to allocate register map\n");
353		return PTR_ERR(data->regmap);
354	}
355
356	i2c_set_clientdata(client, data);
357
358	err = devm_clk_hw_register(&client->dev, &data->hw);
359	if (err) {
360		dev_err(&client->dev, "clock registration failed\n");
361		return err;
362	}
363	err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
364					  &data->hw);
365	if (err) {
366		dev_err(&client->dev, "unable to add clk provider\n");
367		return err;
368	}
369
370	return 0;
371}
372
373static const struct i2c_device_id si514_id[] = {
374	{ "si514", 0 },
375	{ }
376};
377MODULE_DEVICE_TABLE(i2c, si514_id);
378
379static const struct of_device_id clk_si514_of_match[] = {
380	{ .compatible = "silabs,si514" },
381	{ },
382};
383MODULE_DEVICE_TABLE(of, clk_si514_of_match);
384
385static struct i2c_driver si514_driver = {
386	.driver = {
387		.name = "si514",
388		.of_match_table = clk_si514_of_match,
389	},
390	.probe		= si514_probe,
391	.id_table	= si514_id,
392};
393module_i2c_driver(si514_driver);
394
395MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
396MODULE_DESCRIPTION("Si514 driver");
397MODULE_LICENSE("GPL");
398