xref: /linux/drivers/clk/clk-si570.c (revision 0ea5c948cb64bab5bc7a5516774eb8536f05aa0d)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
4  *
5  * Copyright (C) 2010, 2011 Ericsson AB.
6  * Copyright (C) 2011 Guenter Roeck.
7  * Copyright (C) 2011 - 2021 Xilinx Inc.
8  *
9  * Author: Guenter Roeck <guenter.roeck@ericsson.com>
10  *	   Sören Brinkmann <soren.brinkmann@xilinx.com>
11  */
12 
13 #include <linux/clk.h>
14 #include <linux/clk-provider.h>
15 #include <linux/delay.h>
16 #include <linux/module.h>
17 #include <linux/i2c.h>
18 #include <linux/regmap.h>
19 #include <linux/slab.h>
20 
21 /* Si570 registers */
22 #define SI570_REG_HS_N1		7
23 #define SI570_REG_N1_RFREQ0	8
24 #define SI570_REG_RFREQ1	9
25 #define SI570_REG_RFREQ2	10
26 #define SI570_REG_RFREQ3	11
27 #define SI570_REG_RFREQ4	12
28 #define SI570_REG_CONTROL	135
29 #define SI570_REG_FREEZE_DCO	137
30 #define SI570_DIV_OFFSET_7PPM	6
31 
32 #define HS_DIV_SHIFT		5
33 #define HS_DIV_MASK		0xe0
34 #define HS_DIV_OFFSET		4
35 #define N1_6_2_MASK		0x1f
36 #define N1_1_0_MASK		0xc0
37 #define RFREQ_37_32_MASK	0x3f
38 
39 #define SI570_MIN_FREQ		10000000L
40 #define SI570_MAX_FREQ		1417500000L
41 #define SI598_MAX_FREQ		525000000L
42 
43 #define FDCO_MIN		4850000000LL
44 #define FDCO_MAX		5670000000LL
45 
46 #define SI570_CNTRL_RECALL	(1 << 0)
47 #define SI570_CNTRL_FREEZE_M	(1 << 5)
48 #define SI570_CNTRL_NEWFREQ	(1 << 6)
49 
50 #define SI570_FREEZE_DCO	(1 << 4)
51 
52 /**
53  * struct clk_si570_info:
54  * @max_freq:	Maximum frequency for this device
55  * @has_temperature_stability: Device support temperature stability
56  */
57 struct clk_si570_info {
58 	u64 max_freq;
59 	bool has_temperature_stability;
60 };
61 
62 /**
63  * struct clk_si570:
64  * @hw:	Clock hw struct
65  * @regmap:	Device's regmap
66  * @div_offset:	Rgister offset for dividers
67  * @info:	Device info
68  * @fxtal:	Factory xtal frequency
69  * @n1:		Clock divider N1
70  * @hs_div:	Clock divider HSDIV
71  * @rfreq:	Clock multiplier RFREQ
72  * @frequency:	Current output frequency
73  * @i2c_client:	I2C client pointer
74  */
75 struct clk_si570 {
76 	struct clk_hw hw;
77 	struct regmap *regmap;
78 	unsigned int div_offset;
79 	const struct clk_si570_info *info;
80 	u64 fxtal;
81 	unsigned int n1;
82 	unsigned int hs_div;
83 	u64 rfreq;
84 	u64 frequency;
85 	struct i2c_client *i2c_client;
86 };
87 #define to_clk_si570(_hw)	container_of(_hw, struct clk_si570, hw)
88 
89 /**
90  * si570_get_divs() - Read clock dividers from HW
91  * @data:	Pointer to struct clk_si570
92  * @rfreq:	Fractional multiplier (output)
93  * @n1:		Divider N1 (output)
94  * @hs_div:	Divider HSDIV (output)
95  * Returns 0 on success, negative errno otherwise.
96  *
97  * Retrieve clock dividers and multipliers from the HW.
98  */
si570_get_divs(struct clk_si570 * data,u64 * rfreq,unsigned int * n1,unsigned int * hs_div)99 static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
100 		unsigned int *n1, unsigned int *hs_div)
101 {
102 	int err;
103 	u8 reg[6];
104 	u64 tmp;
105 
106 	err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
107 			reg, ARRAY_SIZE(reg));
108 	if (err)
109 		return err;
110 
111 	*hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
112 	*n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
113 	/* Handle invalid cases */
114 	if (*n1 > 1)
115 		*n1 &= ~1;
116 
117 	tmp = reg[1] & RFREQ_37_32_MASK;
118 	tmp = (tmp << 8) + reg[2];
119 	tmp = (tmp << 8) + reg[3];
120 	tmp = (tmp << 8) + reg[4];
121 	tmp = (tmp << 8) + reg[5];
122 	*rfreq = tmp;
123 
124 	return 0;
125 }
126 
127 /**
128  * si570_get_defaults() - Get default values
129  * @data:	Driver data structure
130  * @fout:	Factory frequency output
131  * @skip_recall:	If true, don't recall NVM into RAM
132  * Returns 0 on success, negative errno otherwise.
133  */
si570_get_defaults(struct clk_si570 * data,u64 fout,bool skip_recall)134 static int si570_get_defaults(struct clk_si570 *data, u64 fout,
135 			      bool skip_recall)
136 {
137 	int err;
138 	u64 fdco;
139 
140 	if (!skip_recall)
141 		regmap_write(data->regmap, SI570_REG_CONTROL,
142 			     SI570_CNTRL_RECALL);
143 
144 	err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
145 	if (err)
146 		return err;
147 
148 	/*
149 	 * Accept optional precision loss to avoid arithmetic overflows.
150 	 * Acceptable per Silicon Labs Application Note AN334.
151 	 */
152 	fdco = fout * data->n1 * data->hs_div;
153 	if (fdco >= (1LL << 36))
154 		data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
155 	else
156 		data->fxtal = div64_u64(fdco << 28, data->rfreq);
157 
158 	data->frequency = fout;
159 
160 	return 0;
161 }
162 
163 /**
164  * si570_update_rfreq() - Update clock multiplier
165  * @data:	Driver data structure
166  * Passes on regmap_bulk_write() return value.
167  */
si570_update_rfreq(struct clk_si570 * data)168 static int si570_update_rfreq(struct clk_si570 *data)
169 {
170 	u8 reg[5];
171 
172 	reg[0] = ((data->n1 - 1) << 6) |
173 		((data->rfreq >> 32) & RFREQ_37_32_MASK);
174 	reg[1] = (data->rfreq >> 24) & 0xff;
175 	reg[2] = (data->rfreq >> 16) & 0xff;
176 	reg[3] = (data->rfreq >> 8) & 0xff;
177 	reg[4] = data->rfreq & 0xff;
178 
179 	return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
180 			data->div_offset, reg, ARRAY_SIZE(reg));
181 }
182 
183 /**
184  * si570_calc_divs() - Caluclate clock dividers
185  * @frequency:	Target frequency
186  * @data:	Driver data structure
187  * @out_rfreq:	RFREG fractional multiplier (output)
188  * @out_n1:	Clock divider N1 (output)
189  * @out_hs_div:	Clock divider HSDIV (output)
190  * Returns 0 on success, negative errno otherwise.
191  *
192  * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
193  * (@out_rfreq) for a given target @frequency.
194  */
si570_calc_divs(unsigned long frequency,struct clk_si570 * data,u64 * out_rfreq,unsigned int * out_n1,unsigned int * out_hs_div)195 static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
196 		u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
197 {
198 	int i;
199 	unsigned int n1, hs_div;
200 	u64 fdco, best_fdco = ULLONG_MAX;
201 	static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
202 
203 	for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
204 		hs_div = si570_hs_div_values[i];
205 		/* Calculate lowest possible value for n1 */
206 		n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
207 		if (!n1 || (n1 & 1))
208 			n1++;
209 		while (n1 <= 128) {
210 			fdco = (u64)frequency * (u64)hs_div * (u64)n1;
211 			if (fdco > FDCO_MAX)
212 				break;
213 			if (fdco >= FDCO_MIN && fdco < best_fdco) {
214 				*out_n1 = n1;
215 				*out_hs_div = hs_div;
216 				*out_rfreq = div64_u64(fdco << 28, data->fxtal);
217 				best_fdco = fdco;
218 			}
219 			n1 += (n1 == 1 ? 1 : 2);
220 		}
221 	}
222 
223 	if (best_fdco == ULLONG_MAX)
224 		return -EINVAL;
225 
226 	return 0;
227 }
228 
si570_recalc_rate(struct clk_hw * hw,unsigned long parent_rate)229 static unsigned long si570_recalc_rate(struct clk_hw *hw,
230 		unsigned long parent_rate)
231 {
232 	int err;
233 	u64 rfreq, rate;
234 	unsigned int n1, hs_div;
235 	struct clk_si570 *data = to_clk_si570(hw);
236 
237 	err = si570_get_divs(data, &rfreq, &n1, &hs_div);
238 	if (err) {
239 		dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
240 		return data->frequency;
241 	}
242 
243 	rfreq = div_u64(rfreq, hs_div * n1);
244 	rate = (data->fxtal * rfreq) >> 28;
245 
246 	return rate;
247 }
248 
si570_round_rate(struct clk_hw * hw,unsigned long rate,unsigned long * parent_rate)249 static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
250 		unsigned long *parent_rate)
251 {
252 	int err;
253 	u64 rfreq;
254 	unsigned int n1, hs_div;
255 	struct clk_si570 *data = to_clk_si570(hw);
256 
257 	if (!rate)
258 		return 0;
259 
260 	if (div64_u64(abs(rate - data->frequency) * 10000LL,
261 				data->frequency) < 35) {
262 		rfreq = div64_u64((data->rfreq * rate) +
263 				div64_u64(data->frequency, 2), data->frequency);
264 		n1 = data->n1;
265 		hs_div = data->hs_div;
266 
267 	} else {
268 		err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
269 		if (err) {
270 			dev_err(&data->i2c_client->dev,
271 					"unable to round rate\n");
272 			return 0;
273 		}
274 	}
275 
276 	return rate;
277 }
278 
279 /**
280  * si570_set_frequency() - Adjust output frequency
281  * @data:	Driver data structure
282  * @frequency:	Target frequency
283  * Returns 0 on success.
284  *
285  * Update output frequency for big frequency changes (> 3,500 ppm).
286  */
si570_set_frequency(struct clk_si570 * data,unsigned long frequency)287 static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
288 {
289 	int err;
290 
291 	err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
292 			&data->hs_div);
293 	if (err)
294 		return err;
295 
296 	/*
297 	 * The DCO reg should be accessed with a read-modify-write operation
298 	 * per AN334
299 	 */
300 	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
301 	regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
302 			((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
303 			(((data->n1 - 1) >> 2) & N1_6_2_MASK));
304 	si570_update_rfreq(data);
305 	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
306 	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);
307 
308 	/* Applying a new frequency can take up to 10ms */
309 	usleep_range(10000, 12000);
310 
311 	return 0;
312 }
313 
314 /**
315  * si570_set_frequency_small() - Adjust output frequency
316  * @data:	Driver data structure
317  * @frequency:	Target frequency
318  * Returns 0 on success.
319  *
320  * Update output frequency for small frequency changes (< 3,500 ppm).
321  */
si570_set_frequency_small(struct clk_si570 * data,unsigned long frequency)322 static int si570_set_frequency_small(struct clk_si570 *data,
323 				     unsigned long frequency)
324 {
325 	/*
326 	 * This is a re-implementation of DIV_ROUND_CLOSEST
327 	 * using the div64_u64 function lieu of letting the compiler
328 	 * insert EABI calls
329 	 */
330 	data->rfreq = div64_u64((data->rfreq * frequency) +
331 			div_u64(data->frequency, 2), data->frequency);
332 	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
333 	si570_update_rfreq(data);
334 	regmap_write(data->regmap, SI570_REG_CONTROL, 0);
335 
336 	/* Applying a new frequency (small change) can take up to 100us */
337 	usleep_range(100, 200);
338 
339 	return 0;
340 }
341 
si570_set_rate(struct clk_hw * hw,unsigned long rate,unsigned long parent_rate)342 static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
343 		unsigned long parent_rate)
344 {
345 	struct clk_si570 *data = to_clk_si570(hw);
346 	struct i2c_client *client = data->i2c_client;
347 	int err;
348 
349 	if (rate < SI570_MIN_FREQ || rate > data->info->max_freq) {
350 		dev_err(&client->dev,
351 			"requested frequency %lu Hz is out of range\n", rate);
352 		return -EINVAL;
353 	}
354 
355 	if (div64_u64(abs(rate - data->frequency) * 10000LL,
356 				data->frequency) < 35)
357 		err = si570_set_frequency_small(data, rate);
358 	else
359 		err = si570_set_frequency(data, rate);
360 
361 	if (err)
362 		return err;
363 
364 	data->frequency = rate;
365 
366 	return 0;
367 }
368 
369 static const struct clk_ops si570_clk_ops = {
370 	.recalc_rate = si570_recalc_rate,
371 	.round_rate = si570_round_rate,
372 	.set_rate = si570_set_rate,
373 };
374 
si570_regmap_is_volatile(struct device * dev,unsigned int reg)375 static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
376 {
377 	switch (reg) {
378 	case SI570_REG_CONTROL:
379 		return true;
380 	default:
381 		return false;
382 	}
383 }
384 
si570_regmap_is_writeable(struct device * dev,unsigned int reg)385 static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
386 {
387 	switch (reg) {
388 	case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
389 	case SI570_REG_CONTROL:
390 	case SI570_REG_FREEZE_DCO:
391 		return true;
392 	default:
393 		return false;
394 	}
395 }
396 
397 static const struct regmap_config si570_regmap_config = {
398 	.reg_bits = 8,
399 	.val_bits = 8,
400 	.cache_type = REGCACHE_MAPLE,
401 	.max_register = 137,
402 	.writeable_reg = si570_regmap_is_writeable,
403 	.volatile_reg = si570_regmap_is_volatile,
404 };
405 
si570_probe(struct i2c_client * client)406 static int si570_probe(struct i2c_client *client)
407 {
408 	struct clk_si570 *data;
409 	struct clk_init_data init;
410 	u32 initial_fout, factory_fout, stability;
411 	bool skip_recall;
412 	int err;
413 
414 	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
415 	if (!data)
416 		return -ENOMEM;
417 
418 	init.ops = &si570_clk_ops;
419 	init.flags = 0;
420 	init.num_parents = 0;
421 	data->hw.init = &init;
422 	data->i2c_client = client;
423 
424 	data->info = i2c_get_match_data(client);
425 	if (data->info->has_temperature_stability) {
426 		err = of_property_read_u32(client->dev.of_node,
427 				"temperature-stability", &stability);
428 		if (err) {
429 			dev_err(&client->dev,
430 				  "'temperature-stability' property missing\n");
431 			return err;
432 		}
433 		/* adjust register offsets for 7ppm devices */
434 		if (stability == 7)
435 			data->div_offset = SI570_DIV_OFFSET_7PPM;
436 	}
437 
438 	if (of_property_read_string(client->dev.of_node, "clock-output-names",
439 			&init.name))
440 		init.name = client->dev.of_node->name;
441 
442 	err = of_property_read_u32(client->dev.of_node, "factory-fout",
443 			&factory_fout);
444 	if (err) {
445 		dev_err(&client->dev, "'factory-fout' property missing\n");
446 		return err;
447 	}
448 
449 	skip_recall = of_property_read_bool(client->dev.of_node,
450 					    "silabs,skip-recall");
451 
452 	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
453 	if (IS_ERR(data->regmap)) {
454 		dev_err(&client->dev, "failed to allocate register map\n");
455 		return PTR_ERR(data->regmap);
456 	}
457 
458 	i2c_set_clientdata(client, data);
459 	err = si570_get_defaults(data, factory_fout, skip_recall);
460 	if (err)
461 		return err;
462 
463 	err = devm_clk_hw_register(&client->dev, &data->hw);
464 	if (err) {
465 		dev_err(&client->dev, "clock registration failed\n");
466 		return err;
467 	}
468 	err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
469 					  &data->hw);
470 	if (err) {
471 		dev_err(&client->dev, "unable to add clk provider\n");
472 		return err;
473 	}
474 
475 	/* Read the requested initial output frequency from device tree */
476 	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
477 				&initial_fout)) {
478 		err = clk_set_rate(data->hw.clk, initial_fout);
479 		if (err)
480 			return err;
481 	}
482 
483 	/* Display a message indicating that we've successfully registered */
484 	dev_info(&client->dev, "registered, current frequency %llu Hz\n",
485 			data->frequency);
486 
487 	return 0;
488 }
489 
490 static const struct clk_si570_info clk_si570_info = {
491 	.max_freq = SI570_MAX_FREQ,
492 	.has_temperature_stability = true,
493 };
494 
495 static const struct clk_si570_info clk_si590_info = {
496 	.max_freq = SI598_MAX_FREQ,
497 };
498 
499 static const struct i2c_device_id si570_id[] = {
500 	{ "si570", (kernel_ulong_t)&clk_si570_info },
501 	{ "si571", (kernel_ulong_t)&clk_si570_info },
502 	{ "si598", (kernel_ulong_t)&clk_si590_info },
503 	{ "si599", (kernel_ulong_t)&clk_si590_info },
504 	{ }
505 };
506 MODULE_DEVICE_TABLE(i2c, si570_id);
507 
508 static const struct of_device_id clk_si570_of_match[] = {
509 	{ .compatible = "silabs,si570", .data = &clk_si570_info },
510 	{ .compatible = "silabs,si571", .data = &clk_si570_info },
511 	{ .compatible = "silabs,si598", .data = &clk_si590_info },
512 	{ .compatible = "silabs,si599", .data = &clk_si590_info },
513 	{ }
514 };
515 MODULE_DEVICE_TABLE(of, clk_si570_of_match);
516 
517 static struct i2c_driver si570_driver = {
518 	.driver = {
519 		.name = "si570",
520 		.of_match_table = clk_si570_of_match,
521 	},
522 	.probe		= si570_probe,
523 	.id_table	= si570_id,
524 };
525 module_i2c_driver(si570_driver);
526 
527 MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
528 MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
529 MODULE_DESCRIPTION("Si570 driver");
530 MODULE_LICENSE("GPL");
531