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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:
54 * @hw: Clock hw struct
55 * @regmap: Device's regmap
56 * @div_offset: Rgister offset for dividers
57 * @max_freq: Maximum frequency for this device
58 * @fxtal: Factory xtal frequency
59 * @n1: Clock divider N1
60 * @hs_div: Clock divider HSDIV
61 * @rfreq: Clock multiplier RFREQ
62 * @frequency: Current output frequency
63 * @i2c_client: I2C client pointer
64 */
65struct clk_si570 {
66 struct clk_hw hw;
67 struct regmap *regmap;
68 unsigned int div_offset;
69 u64 max_freq;
70 u64 fxtal;
71 unsigned int n1;
72 unsigned int hs_div;
73 u64 rfreq;
74 u64 frequency;
75 struct i2c_client *i2c_client;
76};
77#define to_clk_si570(_hw) container_of(_hw, struct clk_si570, hw)
78
79enum clk_si570_variant {
80 si57x,
81 si59x
82};
83
84/**
85 * si570_get_divs() - Read clock dividers from HW
86 * @data: Pointer to struct clk_si570
87 * @rfreq: Fractional multiplier (output)
88 * @n1: Divider N1 (output)
89 * @hs_div: Divider HSDIV (output)
90 * Returns 0 on success, negative errno otherwise.
91 *
92 * Retrieve clock dividers and multipliers from the HW.
93 */
94static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
95 unsigned int *n1, unsigned int *hs_div)
96{
97 int err;
98 u8 reg[6];
99 u64 tmp;
100
101 err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
102 reg, ARRAY_SIZE(reg));
103 if (err)
104 return err;
105
106 *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
107 *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
108 /* Handle invalid cases */
109 if (*n1 > 1)
110 *n1 &= ~1;
111
112 tmp = reg[1] & RFREQ_37_32_MASK;
113 tmp = (tmp << 8) + reg[2];
114 tmp = (tmp << 8) + reg[3];
115 tmp = (tmp << 8) + reg[4];
116 tmp = (tmp << 8) + reg[5];
117 *rfreq = tmp;
118
119 return 0;
120}
121
122/**
123 * si570_get_defaults() - Get default values
124 * @data: Driver data structure
125 * @fout: Factory frequency output
126 * @skip_recall: If true, don't recall NVM into RAM
127 * Returns 0 on success, negative errno otherwise.
128 */
129static int si570_get_defaults(struct clk_si570 *data, u64 fout,
130 bool skip_recall)
131{
132 int err;
133 u64 fdco;
134
135 if (!skip_recall)
136 regmap_write(data->regmap, SI570_REG_CONTROL,
137 SI570_CNTRL_RECALL);
138
139 err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
140 if (err)
141 return err;
142
143 /*
144 * Accept optional precision loss to avoid arithmetic overflows.
145 * Acceptable per Silicon Labs Application Note AN334.
146 */
147 fdco = fout * data->n1 * data->hs_div;
148 if (fdco >= (1LL << 36))
149 data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
150 else
151 data->fxtal = div64_u64(fdco << 28, data->rfreq);
152
153 data->frequency = fout;
154
155 return 0;
156}
157
158/**
159 * si570_update_rfreq() - Update clock multiplier
160 * @data: Driver data structure
161 * Passes on regmap_bulk_write() return value.
162 */
163static int si570_update_rfreq(struct clk_si570 *data)
164{
165 u8 reg[5];
166
167 reg[0] = ((data->n1 - 1) << 6) |
168 ((data->rfreq >> 32) & RFREQ_37_32_MASK);
169 reg[1] = (data->rfreq >> 24) & 0xff;
170 reg[2] = (data->rfreq >> 16) & 0xff;
171 reg[3] = (data->rfreq >> 8) & 0xff;
172 reg[4] = data->rfreq & 0xff;
173
174 return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
175 data->div_offset, reg, ARRAY_SIZE(reg));
176}
177
178/**
179 * si570_calc_divs() - Caluclate clock dividers
180 * @frequency: Target frequency
181 * @data: Driver data structure
182 * @out_rfreq: RFREG fractional multiplier (output)
183 * @out_n1: Clock divider N1 (output)
184 * @out_hs_div: Clock divider HSDIV (output)
185 * Returns 0 on success, negative errno otherwise.
186 *
187 * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
188 * (@out_rfreq) for a given target @frequency.
189 */
190static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
191 u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
192{
193 int i;
194 unsigned int n1, hs_div;
195 u64 fdco, best_fdco = ULLONG_MAX;
196 static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
197
198 for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
199 hs_div = si570_hs_div_values[i];
200 /* Calculate lowest possible value for n1 */
201 n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
202 if (!n1 || (n1 & 1))
203 n1++;
204 while (n1 <= 128) {
205 fdco = (u64)frequency * (u64)hs_div * (u64)n1;
206 if (fdco > FDCO_MAX)
207 break;
208 if (fdco >= FDCO_MIN && fdco < best_fdco) {
209 *out_n1 = n1;
210 *out_hs_div = hs_div;
211 *out_rfreq = div64_u64(fdco << 28, data->fxtal);
212 best_fdco = fdco;
213 }
214 n1 += (n1 == 1 ? 1 : 2);
215 }
216 }
217
218 if (best_fdco == ULLONG_MAX)
219 return -EINVAL;
220
221 return 0;
222}
223
224static unsigned long si570_recalc_rate(struct clk_hw *hw,
225 unsigned long parent_rate)
226{
227 int err;
228 u64 rfreq, rate;
229 unsigned int n1, hs_div;
230 struct clk_si570 *data = to_clk_si570(hw);
231
232 err = si570_get_divs(data, &rfreq, &n1, &hs_div);
233 if (err) {
234 dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
235 return data->frequency;
236 }
237
238 rfreq = div_u64(rfreq, hs_div * n1);
239 rate = (data->fxtal * rfreq) >> 28;
240
241 return rate;
242}
243
244static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
245 unsigned long *parent_rate)
246{
247 int err;
248 u64 rfreq;
249 unsigned int n1, hs_div;
250 struct clk_si570 *data = to_clk_si570(hw);
251
252 if (!rate)
253 return 0;
254
255 if (div64_u64(abs(rate - data->frequency) * 10000LL,
256 data->frequency) < 35) {
257 rfreq = div64_u64((data->rfreq * rate) +
258 div64_u64(data->frequency, 2), data->frequency);
259 n1 = data->n1;
260 hs_div = data->hs_div;
261
262 } else {
263 err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
264 if (err) {
265 dev_err(&data->i2c_client->dev,
266 "unable to round rate\n");
267 return 0;
268 }
269 }
270
271 return rate;
272}
273
274/**
275 * si570_set_frequency() - Adjust output frequency
276 * @data: Driver data structure
277 * @frequency: Target frequency
278 * Returns 0 on success.
279 *
280 * Update output frequency for big frequency changes (> 3,500 ppm).
281 */
282static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
283{
284 int err;
285
286 err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
287 &data->hs_div);
288 if (err)
289 return err;
290
291 /*
292 * The DCO reg should be accessed with a read-modify-write operation
293 * per AN334
294 */
295 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
296 regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
297 ((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
298 (((data->n1 - 1) >> 2) & N1_6_2_MASK));
299 si570_update_rfreq(data);
300 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
301 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);
302
303 /* Applying a new frequency can take up to 10ms */
304 usleep_range(10000, 12000);
305
306 return 0;
307}
308
309/**
310 * si570_set_frequency_small() - Adjust output frequency
311 * @data: Driver data structure
312 * @frequency: Target frequency
313 * Returns 0 on success.
314 *
315 * Update output frequency for small frequency changes (< 3,500 ppm).
316 */
317static int si570_set_frequency_small(struct clk_si570 *data,
318 unsigned long frequency)
319{
320 /*
321 * This is a re-implementation of DIV_ROUND_CLOSEST
322 * using the div64_u64 function lieu of letting the compiler
323 * insert EABI calls
324 */
325 data->rfreq = div64_u64((data->rfreq * frequency) +
326 div_u64(data->frequency, 2), data->frequency);
327 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
328 si570_update_rfreq(data);
329 regmap_write(data->regmap, SI570_REG_CONTROL, 0);
330
331 /* Applying a new frequency (small change) can take up to 100us */
332 usleep_range(100, 200);
333
334 return 0;
335}
336
337static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
338 unsigned long parent_rate)
339{
340 struct clk_si570 *data = to_clk_si570(hw);
341 struct i2c_client *client = data->i2c_client;
342 int err;
343
344 if (rate < SI570_MIN_FREQ || rate > data->max_freq) {
345 dev_err(&client->dev,
346 "requested frequency %lu Hz is out of range\n", rate);
347 return -EINVAL;
348 }
349
350 if (div64_u64(abs(rate - data->frequency) * 10000LL,
351 data->frequency) < 35)
352 err = si570_set_frequency_small(data, rate);
353 else
354 err = si570_set_frequency(data, rate);
355
356 if (err)
357 return err;
358
359 data->frequency = rate;
360
361 return 0;
362}
363
364static const struct clk_ops si570_clk_ops = {
365 .recalc_rate = si570_recalc_rate,
366 .round_rate = si570_round_rate,
367 .set_rate = si570_set_rate,
368};
369
370static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
371{
372 switch (reg) {
373 case SI570_REG_CONTROL:
374 return true;
375 default:
376 return false;
377 }
378}
379
380static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
381{
382 switch (reg) {
383 case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
384 case SI570_REG_CONTROL:
385 case SI570_REG_FREEZE_DCO:
386 return true;
387 default:
388 return false;
389 }
390}
391
392static const struct regmap_config si570_regmap_config = {
393 .reg_bits = 8,
394 .val_bits = 8,
395 .cache_type = REGCACHE_RBTREE,
396 .max_register = 137,
397 .writeable_reg = si570_regmap_is_writeable,
398 .volatile_reg = si570_regmap_is_volatile,
399};
400
401static int si570_probe(struct i2c_client *client,
402 const struct i2c_device_id *id)
403{
404 struct clk_si570 *data;
405 struct clk_init_data init;
406 u32 initial_fout, factory_fout, stability;
407 bool skip_recall;
408 int err;
409 enum clk_si570_variant variant = id->driver_data;
410
411 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
412 if (!data)
413 return -ENOMEM;
414
415 init.ops = &si570_clk_ops;
416 init.flags = 0;
417 init.num_parents = 0;
418 data->hw.init = &init;
419 data->i2c_client = client;
420
421 if (variant == si57x) {
422 err = of_property_read_u32(client->dev.of_node,
423 "temperature-stability", &stability);
424 if (err) {
425 dev_err(&client->dev,
426 "'temperature-stability' property missing\n");
427 return err;
428 }
429 /* adjust register offsets for 7ppm devices */
430 if (stability == 7)
431 data->div_offset = SI570_DIV_OFFSET_7PPM;
432
433 data->max_freq = SI570_MAX_FREQ;
434 } else {
435 data->max_freq = SI598_MAX_FREQ;
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 = of_clk_add_hw_provider(client->dev.of_node, 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 of_clk_del_provider(client->dev.of_node);
481 return err;
482 }
483 }
484
485 /* Display a message indicating that we've successfully registered */
486 dev_info(&client->dev, "registered, current frequency %llu Hz\n",
487 data->frequency);
488
489 return 0;
490}
491
492static int si570_remove(struct i2c_client *client)
493{
494 of_clk_del_provider(client->dev.of_node);
495 return 0;
496}
497
498static const struct i2c_device_id si570_id[] = {
499 { "si570", si57x },
500 { "si571", si57x },
501 { "si598", si59x },
502 { "si599", si59x },
503 { }
504};
505MODULE_DEVICE_TABLE(i2c, si570_id);
506
507static const struct of_device_id clk_si570_of_match[] = {
508 { .compatible = "silabs,si570" },
509 { .compatible = "silabs,si571" },
510 { .compatible = "silabs,si598" },
511 { .compatible = "silabs,si599" },
512 { },
513};
514MODULE_DEVICE_TABLE(of, clk_si570_of_match);
515
516static struct i2c_driver si570_driver = {
517 .driver = {
518 .name = "si570",
519 .of_match_table = clk_si570_of_match,
520 },
521 .probe = si570_probe,
522 .remove = si570_remove,
523 .id_table = si570_id,
524};
525module_i2c_driver(si570_driver);
526
527MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
528MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
529MODULE_DESCRIPTION("Si570 driver");
530MODULE_LICENSE("GPL");