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Soren Brinkmann1459c832013-09-21 16:40:39 -07001/*
2 * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
3 *
4 * Copyright (C) 2010, 2011 Ericsson AB.
5 * Copyright (C) 2011 Guenter Roeck.
6 * Copyright (C) 2011 - 2013 Xilinx Inc.
7 *
8 * Author: Guenter Roeck <guenter.roeck@ericsson.com>
9 * Sören Brinkmann <soren.brinkmann@xilinx.com>
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 */
21
22#include <linux/clk-provider.h>
23#include <linux/delay.h>
24#include <linux/module.h>
25#include <linux/i2c.h>
26#include <linux/regmap.h>
27#include <linux/slab.h>
28
29/* Si570 registers */
30#define SI570_REG_HS_N1 7
31#define SI570_REG_N1_RFREQ0 8
32#define SI570_REG_RFREQ1 9
33#define SI570_REG_RFREQ2 10
34#define SI570_REG_RFREQ3 11
35#define SI570_REG_RFREQ4 12
36#define SI570_REG_CONTROL 135
37#define SI570_REG_FREEZE_DCO 137
38#define SI570_DIV_OFFSET_7PPM 6
39
40#define HS_DIV_SHIFT 5
41#define HS_DIV_MASK 0xe0
42#define HS_DIV_OFFSET 4
43#define N1_6_2_MASK 0x1f
44#define N1_1_0_MASK 0xc0
45#define RFREQ_37_32_MASK 0x3f
46
47#define SI570_MIN_FREQ 10000000L
48#define SI570_MAX_FREQ 1417500000L
49#define SI598_MAX_FREQ 525000000L
50
51#define FDCO_MIN 4850000000LL
52#define FDCO_MAX 5670000000LL
53
54#define SI570_CNTRL_RECALL (1 << 0)
55#define SI570_CNTRL_FREEZE_M (1 << 5)
56#define SI570_CNTRL_NEWFREQ (1 << 6)
57
58#define SI570_FREEZE_DCO (1 << 4)
59
60/**
61 * struct clk_si570:
62 * @hw: Clock hw struct
63 * @regmap: Device's regmap
64 * @div_offset: Rgister offset for dividers
65 * @max_freq: Maximum frequency for this device
66 * @fxtal: Factory xtal frequency
67 * @n1: Clock divider N1
68 * @hs_div: Clock divider HSDIV
69 * @rfreq: Clock multiplier RFREQ
70 * @frequency: Current output frequency
71 * @i2c_client: I2C client pointer
72 */
73struct clk_si570 {
74 struct clk_hw hw;
75 struct regmap *regmap;
76 unsigned int div_offset;
77 u64 max_freq;
78 u64 fxtal;
79 unsigned int n1;
80 unsigned int hs_div;
81 u64 rfreq;
82 u64 frequency;
83 struct i2c_client *i2c_client;
84};
85#define to_clk_si570(_hw) container_of(_hw, struct clk_si570, hw)
86
87enum clk_si570_variant {
88 si57x,
89 si59x
90};
91
92/**
93 * si570_get_divs() - Read clock dividers from HW
94 * @data: Pointer to struct clk_si570
95 * @rfreq: Fractional multiplier (output)
96 * @n1: Divider N1 (output)
97 * @hs_div: Divider HSDIV (output)
98 * Returns 0 on success, negative errno otherwise.
99 *
100 * Retrieve clock dividers and multipliers from the HW.
101 */
102static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
103 unsigned int *n1, unsigned int *hs_div)
104{
105 int err;
106 u8 reg[6];
107 u64 tmp;
108
109 err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
110 reg, ARRAY_SIZE(reg));
111 if (err)
112 return err;
113
114 *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
115 *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
116 /* Handle invalid cases */
117 if (*n1 > 1)
118 *n1 &= ~1;
119
120 tmp = reg[1] & RFREQ_37_32_MASK;
121 tmp = (tmp << 8) + reg[2];
122 tmp = (tmp << 8) + reg[3];
123 tmp = (tmp << 8) + reg[4];
124 tmp = (tmp << 8) + reg[5];
125 *rfreq = tmp;
126
127 return 0;
128}
129
130/**
131 * si570_get_defaults() - Get default values
132 * @data: Driver data structure
133 * @fout: Factory frequency output
134 * Returns 0 on success, negative errno otherwise.
135 */
136static int si570_get_defaults(struct clk_si570 *data, u64 fout)
137{
138 int err;
139 u64 fdco;
140
141 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);
142
143 err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
144 if (err)
145 return err;
146
147 /*
148 * Accept optional precision loss to avoid arithmetic overflows.
149 * Acceptable per Silicon Labs Application Note AN334.
150 */
151 fdco = fout * data->n1 * data->hs_div;
152 if (fdco >= (1LL << 36))
153 data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
154 else
155 data->fxtal = div64_u64(fdco << 28, data->rfreq);
156
157 data->frequency = fout;
158
159 return 0;
160}
161
162/**
163 * si570_update_rfreq() - Update clock multiplier
164 * @data: Driver data structure
165 * Passes on regmap_bulk_write() return value.
166 */
167static int si570_update_rfreq(struct clk_si570 *data)
168{
169 u8 reg[5];
170
171 reg[0] = ((data->n1 - 1) << 6) |
172 ((data->rfreq >> 32) & RFREQ_37_32_MASK);
173 reg[1] = (data->rfreq >> 24) & 0xff;
174 reg[2] = (data->rfreq >> 16) & 0xff;
175 reg[3] = (data->rfreq >> 8) & 0xff;
176 reg[4] = data->rfreq & 0xff;
177
178 return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
179 data->div_offset, reg, ARRAY_SIZE(reg));
180}
181
182/**
183 * si570_calc_divs() - Caluclate clock dividers
184 * @frequency: Target frequency
185 * @data: Driver data structure
186 * @out_rfreq: RFREG fractional multiplier (output)
187 * @out_n1: Clock divider N1 (output)
188 * @out_hs_div: Clock divider HSDIV (output)
189 * Returns 0 on success, negative errno otherwise.
190 *
191 * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
192 * (@out_rfreq) for a given target @frequency.
193 */
194static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
195 u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
196{
197 int i;
198 unsigned int n1, hs_div;
199 u64 fdco, best_fdco = ULLONG_MAX;
200 static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
201
202 for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
203 hs_div = si570_hs_div_values[i];
204 /* Calculate lowest possible value for n1 */
205 n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
206 if (!n1 || (n1 & 1))
207 n1++;
208 while (n1 <= 128) {
209 fdco = (u64)frequency * (u64)hs_div * (u64)n1;
210 if (fdco > FDCO_MAX)
211 break;
212 if (fdco >= FDCO_MIN && fdco < best_fdco) {
213 *out_n1 = n1;
214 *out_hs_div = hs_div;
215 *out_rfreq = div64_u64(fdco << 28, data->fxtal);
216 best_fdco = fdco;
217 }
218 n1 += (n1 == 1 ? 1 : 2);
219 }
220 }
221
222 if (best_fdco == ULLONG_MAX)
223 return -EINVAL;
224
225 return 0;
226}
227
228static unsigned long si570_recalc_rate(struct clk_hw *hw,
229 unsigned long parent_rate)
230{
231 int err;
232 u64 rfreq, rate;
233 unsigned int n1, hs_div;
234 struct clk_si570 *data = to_clk_si570(hw);
235
236 err = si570_get_divs(data, &rfreq, &n1, &hs_div);
237 if (err) {
238 dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
239 return data->frequency;
240 }
241
242 rfreq = div_u64(rfreq, hs_div * n1);
243 rate = (data->fxtal * rfreq) >> 28;
244
245 return rate;
246}
247
248static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
249 unsigned long *parent_rate)
250{
251 int err;
252 u64 rfreq;
253 unsigned int n1, hs_div;
254 struct clk_si570 *data = to_clk_si570(hw);
255
256 if (!rate)
257 return 0;
258
259 if (div64_u64(abs(rate - data->frequency) * 10000LL,
260 data->frequency) < 35) {
261 rfreq = div64_u64((data->rfreq * rate) +
262 div64_u64(data->frequency, 2), data->frequency);
263 n1 = data->n1;
264 hs_div = data->hs_div;
265
266 } else {
267 err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
268 if (err) {
269 dev_err(&data->i2c_client->dev,
270 "unable to round rate\n");
271 return 0;
272 }
273 }
274
275 return rate;
276}
277
278/**
279 * si570_set_frequency() - Adjust output frequency
280 * @data: Driver data structure
281 * @frequency: Target frequency
282 * Returns 0 on success.
283 *
284 * Update output frequency for big frequency changes (> 3,500 ppm).
285 */
286static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
287{
288 int err;
289
290 err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
291 &data->hs_div);
292 if (err)
293 return err;
294
295 /*
296 * The DCO reg should be accessed with a read-modify-write operation
297 * per AN334
298 */
299 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
300 regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
301 ((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
302 (((data->n1 - 1) >> 2) & N1_6_2_MASK));
303 si570_update_rfreq(data);
304 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
305 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);
306
307 /* Applying a new frequency can take up to 10ms */
308 usleep_range(10000, 12000);
309
310 return 0;
311}
312
313/**
314 * si570_set_frequency_small() - Adjust output frequency
315 * @data: Driver data structure
316 * @frequency: Target frequency
317 * Returns 0 on success.
318 *
319 * Update output frequency for small frequency changes (< 3,500 ppm).
320 */
321static int si570_set_frequency_small(struct clk_si570 *data,
322 unsigned long frequency)
323{
324 /*
325 * This is a re-implementation of DIV_ROUND_CLOSEST
326 * using the div64_u64 function lieu of letting the compiler
327 * insert EABI calls
328 */
329 data->rfreq = div64_u64((data->rfreq * frequency) +
330 div_u64(data->frequency, 2), data->frequency);
331 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
332 si570_update_rfreq(data);
333 regmap_write(data->regmap, SI570_REG_CONTROL, 0);
334
335 /* Applying a new frequency (small change) can take up to 100us */
336 usleep_range(100, 200);
337
338 return 0;
339}
340
341static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
342 unsigned long parent_rate)
343{
344 struct clk_si570 *data = to_clk_si570(hw);
345 struct i2c_client *client = data->i2c_client;
346 int err;
347
348 if (rate < SI570_MIN_FREQ || rate > data->max_freq) {
349 dev_err(&client->dev,
350 "requested frequency %lu Hz is out of range\n", rate);
351 return -EINVAL;
352 }
353
354 if (div64_u64(abs(rate - data->frequency) * 10000LL,
355 data->frequency) < 35)
356 err = si570_set_frequency_small(data, rate);
357 else
358 err = si570_set_frequency(data, rate);
359
360 if (err)
361 return err;
362
363 data->frequency = rate;
364
365 return 0;
366}
367
368static const struct clk_ops si570_clk_ops = {
369 .recalc_rate = si570_recalc_rate,
370 .round_rate = si570_round_rate,
371 .set_rate = si570_set_rate,
372};
373
374static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
375{
376 switch (reg) {
377 case SI570_REG_CONTROL:
378 return true;
379 default:
380 return false;
381 }
382}
383
384static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
385{
386 switch (reg) {
387 case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
388 case SI570_REG_CONTROL:
389 case SI570_REG_FREEZE_DCO:
390 return true;
391 default:
392 return false;
393 }
394}
395
396static struct regmap_config si570_regmap_config = {
397 .reg_bits = 8,
398 .val_bits = 8,
399 .cache_type = REGCACHE_RBTREE,
400 .max_register = 137,
401 .writeable_reg = si570_regmap_is_writeable,
402 .volatile_reg = si570_regmap_is_volatile,
403};
404
405static int si570_probe(struct i2c_client *client,
406 const struct i2c_device_id *id)
407{
408 struct clk_si570 *data;
409 struct clk_init_data init;
410 struct clk *clk;
411 u32 initial_fout, factory_fout, stability;
412 int err;
413 enum clk_si570_variant variant = id->driver_data;
414
415 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
416 if (!data)
417 return -ENOMEM;
418
419 init.ops = &si570_clk_ops;
420 init.flags = CLK_IS_ROOT;
421 init.num_parents = 0;
422 data->hw.init = &init;
423 data->i2c_client = client;
424
425 if (variant == si57x) {
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 data->max_freq = SI570_MAX_FREQ;
438 } else {
439 data->max_freq = SI598_MAX_FREQ;
440 }
441
442 if (of_property_read_string(client->dev.of_node, "clock-output-names",
443 &init.name))
444 init.name = client->dev.of_node->name;
445
446 err = of_property_read_u32(client->dev.of_node, "factory-fout",
447 &factory_fout);
448 if (err) {
449 dev_err(&client->dev, "'factory-fout' property missing\n");
450 return err;
451 }
452
453 data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
454 if (IS_ERR(data->regmap)) {
455 dev_err(&client->dev, "failed to allocate register map\n");
456 return PTR_ERR(data->regmap);
457 }
458
459 i2c_set_clientdata(client, data);
460 err = si570_get_defaults(data, factory_fout);
461 if (err)
462 return err;
463
464 clk = devm_clk_register(&client->dev, &data->hw);
465 if (IS_ERR(clk)) {
466 dev_err(&client->dev, "clock registration failed\n");
467 return PTR_ERR(clk);
468 }
469 err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
470 clk);
471 if (err) {
472 dev_err(&client->dev, "unable to add clk provider\n");
473 return err;
474 }
475
476 /* Read the requested initial output frequency from device tree */
477 if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
478 &initial_fout)) {
479 err = clk_set_rate(clk, initial_fout);
480 if (err) {
481 of_clk_del_provider(client->dev.of_node);
482 return err;
483 }
484 }
485
486 /* Display a message indicating that we've successfully registered */
487 dev_info(&client->dev, "registered, current frequency %llu Hz\n",
488 data->frequency);
489
490 return 0;
491}
492
493static int si570_remove(struct i2c_client *client)
494{
495 of_clk_del_provider(client->dev.of_node);
496 return 0;
497}
498
499static const struct i2c_device_id si570_id[] = {
500 { "si570", si57x },
501 { "si571", si57x },
502 { "si598", si59x },
503 { "si599", si59x },
504 { }
505};
506MODULE_DEVICE_TABLE(i2c, si570_id);
507
508static const struct of_device_id clk_si570_of_match[] = {
509 { .compatible = "silabs,si570" },
510 { .compatible = "silabs,si571" },
511 { .compatible = "silabs,si598" },
512 { .compatible = "silabs,si599" },
513 { },
514};
515MODULE_DEVICE_TABLE(of, clk_si570_of_match);
516
517static struct i2c_driver si570_driver = {
518 .driver = {
519 .name = "si570",
Sachin Kamate8ab2f12013-12-21 15:45:27 +0530520 .of_match_table = clk_si570_of_match,
Soren Brinkmann1459c832013-09-21 16:40:39 -0700521 },
522 .probe = si570_probe,
523 .remove = si570_remove,
524 .id_table = si570_id,
525};
526module_i2c_driver(si570_driver);
527
528MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
Michal Simek44731f52014-04-03 17:05:02 +0200529MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
Soren Brinkmann1459c832013-09-21 16:40:39 -0700530MODULE_DESCRIPTION("Si570 driver");
531MODULE_LICENSE("GPL");