xref: /openbmc/linux/drivers/clk/clk-si514.c (revision e53134fe)
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 
55 struct 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 */
63 struct 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 */
71 static 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 static int si514_prepare(struct clk_hw *hw)
78 {
79 	struct clk_si514 *data = to_clk_si514(hw);
80 
81 	return si514_enable_output(data, true);
82 }
83 
84 static void si514_unprepare(struct clk_hw *hw)
85 {
86 	struct clk_si514 *data = to_clk_si514(hw);
87 
88 	si514_enable_output(data, false);
89 }
90 
91 static int si514_is_prepared(struct clk_hw *hw)
92 {
93 	struct clk_si514 *data = to_clk_si514(hw);
94 	unsigned int val;
95 	int err;
96 
97 	err = regmap_read(data->regmap, SI514_REG_CONTROL, &val);
98 	if (err < 0)
99 		return err;
100 
101 	return !!(val & SI514_CONTROL_OE);
102 }
103 
104 /* Retrieve clock multiplier and dividers from hardware */
105 static int si514_get_muldiv(struct clk_si514 *data,
106 	struct clk_si514_muldiv *settings)
107 {
108 	int err;
109 	u8 reg[7];
110 
111 	err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
112 			reg, ARRAY_SIZE(reg));
113 	if (err)
114 		return err;
115 
116 	settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
117 			   (reg[3] & 0x1F) << 24;
118 	settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
119 	settings->ls_div_bits = (reg[6] >> 4) & 0x07;
120 	settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
121 	return 0;
122 }
123 
124 static int si514_set_muldiv(struct clk_si514 *data,
125 	struct clk_si514_muldiv *settings)
126 {
127 	u8 lp;
128 	u8 reg[7];
129 	int err;
130 
131 	/* Calculate LP1/LP2 according to table 13 in the datasheet */
132 	/* 65.259980246 */
133 	if (settings->m_int < 65 ||
134 		(settings->m_int == 65 && settings->m_frac <= 139575831))
135 		lp = 0x22;
136 	/* 67.859763463 */
137 	else if (settings->m_int < 67 ||
138 		(settings->m_int == 67 && settings->m_frac <= 461581994))
139 		lp = 0x23;
140 	/* 72.937624981 */
141 	else if (settings->m_int < 72 ||
142 		(settings->m_int == 72 && settings->m_frac <= 503383578))
143 		lp = 0x33;
144 	/* 75.843265046 */
145 	else if (settings->m_int < 75 ||
146 		(settings->m_int == 75 && settings->m_frac <= 452724474))
147 		lp = 0x34;
148 	else
149 		lp = 0x44;
150 
151 	err = regmap_write(data->regmap, SI514_REG_LP, lp);
152 	if (err < 0)
153 		return err;
154 
155 	reg[0] = settings->m_frac;
156 	reg[1] = settings->m_frac >> 8;
157 	reg[2] = settings->m_frac >> 16;
158 	reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
159 	reg[4] = settings->m_int >> 3;
160 	reg[5] = settings->hs_div;
161 	reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
162 
163 	err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
164 	if (err < 0)
165 		return err;
166 	/*
167 	 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
168 	 * must be written last
169 	 */
170 	return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
171 }
172 
173 /* Calculate divider settings for a given frequency */
174 static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
175 	unsigned long frequency)
176 {
177 	u64 m;
178 	u32 ls_freq;
179 	u32 tmp;
180 	u8 res;
181 
182 	if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
183 		return -EINVAL;
184 
185 	/* Determine the minimum value of LS_DIV and resulting target freq. */
186 	ls_freq = frequency;
187 	if (frequency >= (FVCO_MIN / HS_DIV_MAX))
188 		settings->ls_div_bits = 0;
189 	else {
190 		res = 1;
191 		tmp = 2 * HS_DIV_MAX;
192 		while (tmp <= (HS_DIV_MAX * 32)) {
193 			if ((frequency * tmp) >= FVCO_MIN)
194 				break;
195 			++res;
196 			tmp <<= 1;
197 		}
198 		settings->ls_div_bits = res;
199 		ls_freq = frequency << res;
200 	}
201 
202 	/* Determine minimum HS_DIV, round up to even number */
203 	settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
204 
205 	/* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
206 	m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
207 	do_div(m, FXO);
208 	settings->m_frac = (u32)m & (BIT(29) - 1);
209 	settings->m_int = (u32)(m >> 29);
210 
211 	return 0;
212 }
213 
214 /* Calculate resulting frequency given the register settings */
215 static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
216 {
217 	u64 m = settings->m_frac | ((u64)settings->m_int << 29);
218 	u32 d = settings->hs_div * BIT(settings->ls_div_bits);
219 
220 	return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
221 }
222 
223 static unsigned long si514_recalc_rate(struct clk_hw *hw,
224 		unsigned long parent_rate)
225 {
226 	struct clk_si514 *data = to_clk_si514(hw);
227 	struct clk_si514_muldiv settings;
228 	int err;
229 
230 	err = si514_get_muldiv(data, &settings);
231 	if (err) {
232 		dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
233 		return 0;
234 	}
235 
236 	return si514_calc_rate(&settings);
237 }
238 
239 static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
240 		unsigned long *parent_rate)
241 {
242 	struct clk_si514_muldiv settings;
243 	int err;
244 
245 	if (!rate)
246 		return 0;
247 
248 	err = si514_calc_muldiv(&settings, rate);
249 	if (err)
250 		return err;
251 
252 	return si514_calc_rate(&settings);
253 }
254 
255 /*
256  * Update output frequency for big frequency changes (> 1000 ppm).
257  * The chip supports <1000ppm changes "on the fly", we haven't implemented
258  * that here.
259  */
260 static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
261 		unsigned long parent_rate)
262 {
263 	struct clk_si514 *data = to_clk_si514(hw);
264 	struct clk_si514_muldiv settings;
265 	unsigned int old_oe_state;
266 	int err;
267 
268 	err = si514_calc_muldiv(&settings, rate);
269 	if (err)
270 		return err;
271 
272 	err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
273 	if (err)
274 		return err;
275 
276 	si514_enable_output(data, false);
277 
278 	err = si514_set_muldiv(data, &settings);
279 	if (err < 0)
280 		return err; /* Undefined state now, best to leave disabled */
281 
282 	/* Trigger calibration */
283 	err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
284 	if (err < 0)
285 		return err;
286 
287 	/* Applying a new frequency can take up to 10ms */
288 	usleep_range(10000, 12000);
289 
290 	if (old_oe_state & SI514_CONTROL_OE)
291 		si514_enable_output(data, true);
292 
293 	return err;
294 }
295 
296 static const struct clk_ops si514_clk_ops = {
297 	.prepare = si514_prepare,
298 	.unprepare = si514_unprepare,
299 	.is_prepared = si514_is_prepared,
300 	.recalc_rate = si514_recalc_rate,
301 	.round_rate = si514_round_rate,
302 	.set_rate = si514_set_rate,
303 };
304 
305 static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
306 {
307 	switch (reg) {
308 	case SI514_REG_CONTROL:
309 	case SI514_REG_RESET:
310 		return true;
311 	default:
312 		return false;
313 	}
314 }
315 
316 static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
317 {
318 	switch (reg) {
319 	case SI514_REG_LP:
320 	case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
321 	case SI514_REG_OE_STATE:
322 	case SI514_REG_RESET:
323 	case SI514_REG_CONTROL:
324 		return true;
325 	default:
326 		return false;
327 	}
328 }
329 
330 static const struct regmap_config si514_regmap_config = {
331 	.reg_bits = 8,
332 	.val_bits = 8,
333 	.cache_type = REGCACHE_RBTREE,
334 	.max_register = SI514_REG_CONTROL,
335 	.writeable_reg = si514_regmap_is_writeable,
336 	.volatile_reg = si514_regmap_is_volatile,
337 };
338 
339 static int si514_probe(struct i2c_client *client,
340 		const struct i2c_device_id *id)
341 {
342 	struct clk_si514 *data;
343 	struct clk_init_data init;
344 	int err;
345 
346 	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
347 	if (!data)
348 		return -ENOMEM;
349 
350 	init.ops = &si514_clk_ops;
351 	init.flags = 0;
352 	init.num_parents = 0;
353 	data->hw.init = &init;
354 	data->i2c_client = client;
355 
356 	if (of_property_read_string(client->dev.of_node, "clock-output-names",
357 			&init.name))
358 		init.name = client->dev.of_node->name;
359 
360 	data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
361 	if (IS_ERR(data->regmap)) {
362 		dev_err(&client->dev, "failed to allocate register map\n");
363 		return PTR_ERR(data->regmap);
364 	}
365 
366 	i2c_set_clientdata(client, data);
367 
368 	err = devm_clk_hw_register(&client->dev, &data->hw);
369 	if (err) {
370 		dev_err(&client->dev, "clock registration failed\n");
371 		return err;
372 	}
373 	err = of_clk_add_hw_provider(client->dev.of_node, of_clk_hw_simple_get,
374 				     &data->hw);
375 	if (err) {
376 		dev_err(&client->dev, "unable to add clk provider\n");
377 		return err;
378 	}
379 
380 	return 0;
381 }
382 
383 static int si514_remove(struct i2c_client *client)
384 {
385 	of_clk_del_provider(client->dev.of_node);
386 	return 0;
387 }
388 
389 static const struct i2c_device_id si514_id[] = {
390 	{ "si514", 0 },
391 	{ }
392 };
393 MODULE_DEVICE_TABLE(i2c, si514_id);
394 
395 static const struct of_device_id clk_si514_of_match[] = {
396 	{ .compatible = "silabs,si514" },
397 	{ },
398 };
399 MODULE_DEVICE_TABLE(of, clk_si514_of_match);
400 
401 static struct i2c_driver si514_driver = {
402 	.driver = {
403 		.name = "si514",
404 		.of_match_table = clk_si514_of_match,
405 	},
406 	.probe		= si514_probe,
407 	.remove		= si514_remove,
408 	.id_table	= si514_id,
409 };
410 module_i2c_driver(si514_driver);
411 
412 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
413 MODULE_DESCRIPTION("Si514 driver");
414 MODULE_LICENSE("GPL");
415