1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Driver for Silicon Labs Si544 Programmable Oscillator
4 * Copyright (C) 2018 Topic Embedded Products
5 * Author: Mike Looijmans <mike.looijmans@topic.nl>
6 */
7
8 #include <linux/clk-provider.h>
9 #include <linux/delay.h>
10 #include <linux/math64.h>
11 #include <linux/module.h>
12 #include <linux/i2c.h>
13 #include <linux/regmap.h>
14 #include <linux/slab.h>
15
16 /* I2C registers (decimal as in datasheet) */
17 #define SI544_REG_CONTROL 7
18 #define SI544_REG_OE_STATE 17
19 #define SI544_REG_HS_DIV 23
20 #define SI544_REG_LS_HS_DIV 24
21 #define SI544_REG_FBDIV0 26
22 #define SI544_REG_FBDIV8 27
23 #define SI544_REG_FBDIV16 28
24 #define SI544_REG_FBDIV24 29
25 #define SI544_REG_FBDIV32 30
26 #define SI544_REG_FBDIV40 31
27 #define SI544_REG_FCAL_OVR 69
28 #define SI544_REG_ADPLL_DELTA_M0 231
29 #define SI544_REG_ADPLL_DELTA_M8 232
30 #define SI544_REG_ADPLL_DELTA_M16 233
31 #define SI544_REG_PAGE_SELECT 255
32
33 /* Register values */
34 #define SI544_CONTROL_RESET BIT(7)
35 #define SI544_CONTROL_MS_ICAL2 BIT(3)
36
37 #define SI544_OE_STATE_ODC_OE BIT(0)
38
39 /* Max freq depends on speed grade */
40 #define SI544_MIN_FREQ 200000U
41
42 /* Si544 Internal oscilator runs at 55.05 MHz */
43 #define FXO 55050000U
44
45 /* VCO range is 10.8 .. 12.1 GHz, max depends on speed grade */
46 #define FVCO_MIN 10800000000ULL
47
48 #define HS_DIV_MAX 2046
49 #define HS_DIV_MAX_ODD 33
50
51 /* Lowest frequency synthesizeable using only the HS divider */
52 #define MIN_HSDIV_FREQ (FVCO_MIN / HS_DIV_MAX)
53
54 /* Range and interpretation of the adjustment value */
55 #define DELTA_M_MAX 8161512
56 #define DELTA_M_FRAC_NUM 19
57 #define DELTA_M_FRAC_DEN 20000
58
59 struct clk_si544 {
60 struct clk_hw hw;
61 struct regmap *regmap;
62 struct i2c_client *i2c_client;
63 unsigned long max_freq;
64 };
65 #define to_clk_si544(_hw) container_of(_hw, struct clk_si544, hw)
66
67 /**
68 * struct clk_si544_muldiv - Multiplier/divider settings
69 * @fb_div_frac: integer part of feedback divider (32 bits)
70 * @fb_div_int: fractional part of feedback divider (11 bits)
71 * @hs_div: 1st divider, 5..2046, must be even when >33
72 * @ls_div_bits: 2nd divider, as 2^x, range 0..5
73 * If ls_div_bits is non-zero, hs_div must be even
74 * @delta_m: Frequency shift for small -950..+950 ppm changes, 24 bit
75 */
76 struct clk_si544_muldiv {
77 u32 fb_div_frac;
78 u16 fb_div_int;
79 u16 hs_div;
80 u8 ls_div_bits;
81 s32 delta_m;
82 };
83
84 /* Enables or disables the output driver */
si544_enable_output(struct clk_si544 * data,bool enable)85 static int si544_enable_output(struct clk_si544 *data, bool enable)
86 {
87 return regmap_update_bits(data->regmap, SI544_REG_OE_STATE,
88 SI544_OE_STATE_ODC_OE, enable ? SI544_OE_STATE_ODC_OE : 0);
89 }
90
si544_prepare(struct clk_hw * hw)91 static int si544_prepare(struct clk_hw *hw)
92 {
93 struct clk_si544 *data = to_clk_si544(hw);
94
95 return si544_enable_output(data, true);
96 }
97
si544_unprepare(struct clk_hw * hw)98 static void si544_unprepare(struct clk_hw *hw)
99 {
100 struct clk_si544 *data = to_clk_si544(hw);
101
102 si544_enable_output(data, false);
103 }
104
si544_is_prepared(struct clk_hw * hw)105 static int si544_is_prepared(struct clk_hw *hw)
106 {
107 struct clk_si544 *data = to_clk_si544(hw);
108 unsigned int val;
109 int err;
110
111 err = regmap_read(data->regmap, SI544_REG_OE_STATE, &val);
112 if (err < 0)
113 return err;
114
115 return !!(val & SI544_OE_STATE_ODC_OE);
116 }
117
118 /* Retrieve clock multiplier and dividers from hardware */
si544_get_muldiv(struct clk_si544 * data,struct clk_si544_muldiv * settings)119 static int si544_get_muldiv(struct clk_si544 *data,
120 struct clk_si544_muldiv *settings)
121 {
122 int err;
123 u8 reg[6];
124
125 err = regmap_bulk_read(data->regmap, SI544_REG_HS_DIV, reg, 2);
126 if (err)
127 return err;
128
129 settings->ls_div_bits = (reg[1] >> 4) & 0x07;
130 settings->hs_div = (reg[1] & 0x07) << 8 | reg[0];
131
132 err = regmap_bulk_read(data->regmap, SI544_REG_FBDIV0, reg, 6);
133 if (err)
134 return err;
135
136 settings->fb_div_int = reg[4] | (reg[5] & 0x07) << 8;
137 settings->fb_div_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
138 reg[3] << 24;
139
140 err = regmap_bulk_read(data->regmap, SI544_REG_ADPLL_DELTA_M0, reg, 3);
141 if (err)
142 return err;
143
144 /* Interpret as 24-bit signed number */
145 settings->delta_m = reg[0] << 8 | reg[1] << 16 | reg[2] << 24;
146 settings->delta_m >>= 8;
147
148 return 0;
149 }
150
si544_set_delta_m(struct clk_si544 * data,s32 delta_m)151 static int si544_set_delta_m(struct clk_si544 *data, s32 delta_m)
152 {
153 u8 reg[3];
154
155 reg[0] = delta_m;
156 reg[1] = delta_m >> 8;
157 reg[2] = delta_m >> 16;
158
159 return regmap_bulk_write(data->regmap, SI544_REG_ADPLL_DELTA_M0,
160 reg, 3);
161 }
162
si544_set_muldiv(struct clk_si544 * data,struct clk_si544_muldiv * settings)163 static int si544_set_muldiv(struct clk_si544 *data,
164 struct clk_si544_muldiv *settings)
165 {
166 int err;
167 u8 reg[6];
168
169 reg[0] = settings->hs_div;
170 reg[1] = settings->hs_div >> 8 | settings->ls_div_bits << 4;
171
172 err = regmap_bulk_write(data->regmap, SI544_REG_HS_DIV, reg, 2);
173 if (err < 0)
174 return err;
175
176 reg[0] = settings->fb_div_frac;
177 reg[1] = settings->fb_div_frac >> 8;
178 reg[2] = settings->fb_div_frac >> 16;
179 reg[3] = settings->fb_div_frac >> 24;
180 reg[4] = settings->fb_div_int;
181 reg[5] = settings->fb_div_int >> 8;
182
183 /*
184 * Writing to SI544_REG_FBDIV40 triggers the clock change, so that
185 * must be written last
186 */
187 return regmap_bulk_write(data->regmap, SI544_REG_FBDIV0, reg, 6);
188 }
189
is_valid_frequency(const struct clk_si544 * data,unsigned long frequency)190 static bool is_valid_frequency(const struct clk_si544 *data,
191 unsigned long frequency)
192 {
193 if (frequency < SI544_MIN_FREQ)
194 return false;
195
196 return frequency <= data->max_freq;
197 }
198
199 /* Calculate divider settings for a given frequency */
si544_calc_muldiv(struct clk_si544_muldiv * settings,unsigned long frequency)200 static int si544_calc_muldiv(struct clk_si544_muldiv *settings,
201 unsigned long frequency)
202 {
203 u64 vco;
204 u32 ls_freq;
205 u32 tmp;
206 u8 res;
207
208 /* Determine the minimum value of LS_DIV and resulting target freq. */
209 ls_freq = frequency;
210 settings->ls_div_bits = 0;
211
212 if (frequency >= MIN_HSDIV_FREQ) {
213 settings->ls_div_bits = 0;
214 } else {
215 res = 1;
216 tmp = 2 * HS_DIV_MAX;
217 while (tmp <= (HS_DIV_MAX * 32)) {
218 if (((u64)frequency * tmp) >= FVCO_MIN)
219 break;
220 ++res;
221 tmp <<= 1;
222 }
223 settings->ls_div_bits = res;
224 ls_freq = frequency << res;
225 }
226
227 /* Determine minimum HS_DIV by rounding up */
228 vco = FVCO_MIN + ls_freq - 1;
229 do_div(vco, ls_freq);
230 settings->hs_div = vco;
231
232 /* round up to even number when required */
233 if ((settings->hs_div & 1) &&
234 (settings->hs_div > HS_DIV_MAX_ODD || settings->ls_div_bits))
235 ++settings->hs_div;
236
237 /* Calculate VCO frequency (in 10..12GHz range) */
238 vco = (u64)ls_freq * settings->hs_div;
239
240 /* Calculate the integer part of the feedback divider */
241 tmp = do_div(vco, FXO);
242 settings->fb_div_int = vco;
243
244 /* And the fractional bits using the remainder */
245 vco = (u64)tmp << 32;
246 vco += FXO / 2; /* Round to nearest multiple */
247 do_div(vco, FXO);
248 settings->fb_div_frac = vco;
249
250 /* Reset the frequency adjustment */
251 settings->delta_m = 0;
252
253 return 0;
254 }
255
256 /* Calculate resulting frequency given the register settings */
si544_calc_center_rate(const struct clk_si544_muldiv * settings)257 static unsigned long si544_calc_center_rate(
258 const struct clk_si544_muldiv *settings)
259 {
260 u32 d = settings->hs_div * BIT(settings->ls_div_bits);
261 u64 vco;
262
263 /* Calculate VCO from the fractional part */
264 vco = (u64)settings->fb_div_frac * FXO;
265 vco += (FXO / 2);
266 vco >>= 32;
267
268 /* Add the integer part of the VCO frequency */
269 vco += (u64)settings->fb_div_int * FXO;
270
271 /* Apply divider to obtain the generated frequency */
272 do_div(vco, d);
273
274 return vco;
275 }
276
si544_calc_rate(const struct clk_si544_muldiv * settings)277 static unsigned long si544_calc_rate(const struct clk_si544_muldiv *settings)
278 {
279 unsigned long rate = si544_calc_center_rate(settings);
280 s64 delta = (s64)rate * (DELTA_M_FRAC_NUM * settings->delta_m);
281
282 /*
283 * The clock adjustment is much smaller than 1 Hz, round to the
284 * nearest multiple. Apparently div64_s64 rounds towards zero, hence
285 * check the sign and adjust into the proper direction.
286 */
287 if (settings->delta_m < 0)
288 delta -= ((s64)DELTA_M_MAX * DELTA_M_FRAC_DEN) / 2;
289 else
290 delta += ((s64)DELTA_M_MAX * DELTA_M_FRAC_DEN) / 2;
291 delta = div64_s64(delta, ((s64)DELTA_M_MAX * DELTA_M_FRAC_DEN));
292
293 return rate + delta;
294 }
295
si544_recalc_rate(struct clk_hw * hw,unsigned long parent_rate)296 static unsigned long si544_recalc_rate(struct clk_hw *hw,
297 unsigned long parent_rate)
298 {
299 struct clk_si544 *data = to_clk_si544(hw);
300 struct clk_si544_muldiv settings;
301 int err;
302
303 err = si544_get_muldiv(data, &settings);
304 if (err)
305 return 0;
306
307 return si544_calc_rate(&settings);
308 }
309
si544_round_rate(struct clk_hw * hw,unsigned long rate,unsigned long * parent_rate)310 static long si544_round_rate(struct clk_hw *hw, unsigned long rate,
311 unsigned long *parent_rate)
312 {
313 struct clk_si544 *data = to_clk_si544(hw);
314
315 if (!is_valid_frequency(data, rate))
316 return -EINVAL;
317
318 /* The accuracy is less than 1 Hz, so any rate is possible */
319 return rate;
320 }
321
322 /* Calculates the maximum "small" change, 950 * rate / 1000000 */
si544_max_delta(unsigned long rate)323 static unsigned long si544_max_delta(unsigned long rate)
324 {
325 u64 num = rate;
326
327 num *= DELTA_M_FRAC_NUM;
328 do_div(num, DELTA_M_FRAC_DEN);
329
330 return num;
331 }
332
si544_calc_delta(s32 delta,s32 max_delta)333 static s32 si544_calc_delta(s32 delta, s32 max_delta)
334 {
335 s64 n = (s64)delta * DELTA_M_MAX;
336
337 return div_s64(n, max_delta);
338 }
339
si544_set_rate(struct clk_hw * hw,unsigned long rate,unsigned long parent_rate)340 static int si544_set_rate(struct clk_hw *hw, unsigned long rate,
341 unsigned long parent_rate)
342 {
343 struct clk_si544 *data = to_clk_si544(hw);
344 struct clk_si544_muldiv settings;
345 unsigned long center;
346 long max_delta;
347 long delta;
348 unsigned int old_oe_state;
349 int err;
350
351 if (!is_valid_frequency(data, rate))
352 return -EINVAL;
353
354 /* Try using the frequency adjustment feature for a <= 950ppm change */
355 err = si544_get_muldiv(data, &settings);
356 if (err)
357 return err;
358
359 center = si544_calc_center_rate(&settings);
360 max_delta = si544_max_delta(center);
361 delta = rate - center;
362
363 if (abs(delta) <= max_delta)
364 return si544_set_delta_m(data,
365 si544_calc_delta(delta, max_delta));
366
367 /* Too big for the delta adjustment, need to reprogram */
368 err = si544_calc_muldiv(&settings, rate);
369 if (err)
370 return err;
371
372 err = regmap_read(data->regmap, SI544_REG_OE_STATE, &old_oe_state);
373 if (err)
374 return err;
375
376 si544_enable_output(data, false);
377
378 /* Allow FCAL for this frequency update */
379 err = regmap_write(data->regmap, SI544_REG_FCAL_OVR, 0);
380 if (err < 0)
381 return err;
382
383 err = si544_set_delta_m(data, settings.delta_m);
384 if (err < 0)
385 return err;
386
387 err = si544_set_muldiv(data, &settings);
388 if (err < 0)
389 return err; /* Undefined state now, best to leave disabled */
390
391 /* Trigger calibration */
392 err = regmap_write(data->regmap, SI544_REG_CONTROL,
393 SI544_CONTROL_MS_ICAL2);
394 if (err < 0)
395 return err;
396
397 /* Applying a new frequency can take up to 10ms */
398 usleep_range(10000, 12000);
399
400 if (old_oe_state & SI544_OE_STATE_ODC_OE)
401 si544_enable_output(data, true);
402
403 return err;
404 }
405
406 static const struct clk_ops si544_clk_ops = {
407 .prepare = si544_prepare,
408 .unprepare = si544_unprepare,
409 .is_prepared = si544_is_prepared,
410 .recalc_rate = si544_recalc_rate,
411 .round_rate = si544_round_rate,
412 .set_rate = si544_set_rate,
413 };
414
si544_regmap_is_volatile(struct device * dev,unsigned int reg)415 static bool si544_regmap_is_volatile(struct device *dev, unsigned int reg)
416 {
417 switch (reg) {
418 case SI544_REG_CONTROL:
419 case SI544_REG_FCAL_OVR:
420 return true;
421 default:
422 return false;
423 }
424 }
425
426 static const struct regmap_config si544_regmap_config = {
427 .reg_bits = 8,
428 .val_bits = 8,
429 .cache_type = REGCACHE_MAPLE,
430 .max_register = SI544_REG_PAGE_SELECT,
431 .volatile_reg = si544_regmap_is_volatile,
432 };
433
si544_probe(struct i2c_client * client)434 static int si544_probe(struct i2c_client *client)
435 {
436 struct clk_si544 *data;
437 struct clk_init_data init;
438 int err;
439
440 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
441 if (!data)
442 return -ENOMEM;
443
444 init.ops = &si544_clk_ops;
445 init.flags = 0;
446 init.num_parents = 0;
447 data->hw.init = &init;
448 data->i2c_client = client;
449 data->max_freq = (uintptr_t)i2c_get_match_data(client);
450
451 if (of_property_read_string(client->dev.of_node, "clock-output-names",
452 &init.name))
453 init.name = client->dev.of_node->name;
454
455 data->regmap = devm_regmap_init_i2c(client, &si544_regmap_config);
456 if (IS_ERR(data->regmap))
457 return PTR_ERR(data->regmap);
458
459 i2c_set_clientdata(client, data);
460
461 /* Select page 0, just to be sure, there appear to be no more */
462 err = regmap_write(data->regmap, SI544_REG_PAGE_SELECT, 0);
463 if (err < 0)
464 return err;
465
466 err = devm_clk_hw_register(&client->dev, &data->hw);
467 if (err) {
468 dev_err(&client->dev, "clock registration failed\n");
469 return err;
470 }
471 err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
472 &data->hw);
473 if (err) {
474 dev_err(&client->dev, "unable to add clk provider\n");
475 return err;
476 }
477
478 return 0;
479 }
480
481 static const struct i2c_device_id si544_id[] = {
482 { "si544a", 1500000000 },
483 { "si544b", 800000000 },
484 { "si544c", 350000000 },
485 { }
486 };
487 MODULE_DEVICE_TABLE(i2c, si544_id);
488
489 static const struct of_device_id clk_si544_of_match[] = {
490 { .compatible = "silabs,si544a", .data = (void *)1500000000 },
491 { .compatible = "silabs,si544b", .data = (void *)800000000 },
492 { .compatible = "silabs,si544c", .data = (void *)350000000 },
493 { }
494 };
495 MODULE_DEVICE_TABLE(of, clk_si544_of_match);
496
497 static struct i2c_driver si544_driver = {
498 .driver = {
499 .name = "si544",
500 .of_match_table = clk_si544_of_match,
501 },
502 .probe = si544_probe,
503 .id_table = si544_id,
504 };
505 module_i2c_driver(si544_driver);
506
507 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
508 MODULE_DESCRIPTION("Si544 driver");
509 MODULE_LICENSE("GPL");
510