1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Driver for Silicon Labs Si514 Programmable Oscillator
4 *
5 * Copyright (C) 2015 Topic Embedded Products
6 *
7 * Author: Mike Looijmans <mike.looijmans@topic.nl>
8 */
9
10 #include <linux/clk-provider.h>
11 #include <linux/delay.h>
12 #include <linux/module.h>
13 #include <linux/i2c.h>
14 #include <linux/regmap.h>
15 #include <linux/slab.h>
16
17 /* I2C registers */
18 #define SI514_REG_LP 0
19 #define SI514_REG_M_FRAC1 5
20 #define SI514_REG_M_FRAC2 6
21 #define SI514_REG_M_FRAC3 7
22 #define SI514_REG_M_INT_FRAC 8
23 #define SI514_REG_M_INT 9
24 #define SI514_REG_HS_DIV 10
25 #define SI514_REG_LS_HS_DIV 11
26 #define SI514_REG_OE_STATE 14
27 #define SI514_REG_RESET 128
28 #define SI514_REG_CONTROL 132
29
30 /* Register values */
31 #define SI514_RESET_RST BIT(7)
32
33 #define SI514_CONTROL_FCAL BIT(0)
34 #define SI514_CONTROL_OE BIT(2)
35
36 #define SI514_MIN_FREQ 100000U
37 #define SI514_MAX_FREQ 250000000U
38
39 #define FXO 31980000U
40
41 #define FVCO_MIN 2080000000U
42 #define FVCO_MAX 2500000000U
43
44 #define HS_DIV_MAX 1022
45
46 struct clk_si514 {
47 struct clk_hw hw;
48 struct regmap *regmap;
49 struct i2c_client *i2c_client;
50 };
51 #define to_clk_si514(_hw) container_of(_hw, struct clk_si514, hw)
52
53 /* Multiplier/divider settings */
54 struct clk_si514_muldiv {
55 u32 m_frac; /* 29-bit Fractional part of multiplier M */
56 u8 m_int; /* Integer part of multiplier M, 65..78 */
57 u8 ls_div_bits; /* 2nd divider, as 2^x */
58 u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
59 };
60
61 /* Enables or disables the output driver */
si514_enable_output(struct clk_si514 * data,bool enable)62 static int si514_enable_output(struct clk_si514 *data, bool enable)
63 {
64 return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
65 SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
66 }
67
si514_prepare(struct clk_hw * hw)68 static int si514_prepare(struct clk_hw *hw)
69 {
70 struct clk_si514 *data = to_clk_si514(hw);
71
72 return si514_enable_output(data, true);
73 }
74
si514_unprepare(struct clk_hw * hw)75 static void si514_unprepare(struct clk_hw *hw)
76 {
77 struct clk_si514 *data = to_clk_si514(hw);
78
79 si514_enable_output(data, false);
80 }
81
si514_is_prepared(struct clk_hw * hw)82 static int si514_is_prepared(struct clk_hw *hw)
83 {
84 struct clk_si514 *data = to_clk_si514(hw);
85 unsigned int val;
86 int err;
87
88 err = regmap_read(data->regmap, SI514_REG_CONTROL, &val);
89 if (err < 0)
90 return err;
91
92 return !!(val & SI514_CONTROL_OE);
93 }
94
95 /* Retrieve clock multiplier and dividers from hardware */
si514_get_muldiv(struct clk_si514 * data,struct clk_si514_muldiv * settings)96 static int si514_get_muldiv(struct clk_si514 *data,
97 struct clk_si514_muldiv *settings)
98 {
99 int err;
100 u8 reg[7];
101
102 err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
103 reg, ARRAY_SIZE(reg));
104 if (err)
105 return err;
106
107 settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
108 (reg[3] & 0x1F) << 24;
109 settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
110 settings->ls_div_bits = (reg[6] >> 4) & 0x07;
111 settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
112 return 0;
113 }
114
si514_set_muldiv(struct clk_si514 * data,struct clk_si514_muldiv * settings)115 static int si514_set_muldiv(struct clk_si514 *data,
116 struct clk_si514_muldiv *settings)
117 {
118 u8 lp;
119 u8 reg[7];
120 int err;
121
122 /* Calculate LP1/LP2 according to table 13 in the datasheet */
123 /* 65.259980246 */
124 if (settings->m_int < 65 ||
125 (settings->m_int == 65 && settings->m_frac <= 139575831))
126 lp = 0x22;
127 /* 67.859763463 */
128 else if (settings->m_int < 67 ||
129 (settings->m_int == 67 && settings->m_frac <= 461581994))
130 lp = 0x23;
131 /* 72.937624981 */
132 else if (settings->m_int < 72 ||
133 (settings->m_int == 72 && settings->m_frac <= 503383578))
134 lp = 0x33;
135 /* 75.843265046 */
136 else if (settings->m_int < 75 ||
137 (settings->m_int == 75 && settings->m_frac <= 452724474))
138 lp = 0x34;
139 else
140 lp = 0x44;
141
142 err = regmap_write(data->regmap, SI514_REG_LP, lp);
143 if (err < 0)
144 return err;
145
146 reg[0] = settings->m_frac;
147 reg[1] = settings->m_frac >> 8;
148 reg[2] = settings->m_frac >> 16;
149 reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
150 reg[4] = settings->m_int >> 3;
151 reg[5] = settings->hs_div;
152 reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
153
154 err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
155 if (err < 0)
156 return err;
157 /*
158 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
159 * must be written last
160 */
161 return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
162 }
163
164 /* Calculate divider settings for a given frequency */
si514_calc_muldiv(struct clk_si514_muldiv * settings,unsigned long frequency)165 static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
166 unsigned long frequency)
167 {
168 u64 m;
169 u32 ls_freq;
170 u32 tmp;
171 u8 res;
172
173 if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
174 return -EINVAL;
175
176 /* Determine the minimum value of LS_DIV and resulting target freq. */
177 ls_freq = frequency;
178 if (frequency >= (FVCO_MIN / HS_DIV_MAX))
179 settings->ls_div_bits = 0;
180 else {
181 res = 1;
182 tmp = 2 * HS_DIV_MAX;
183 while (tmp <= (HS_DIV_MAX * 32)) {
184 if ((frequency * tmp) >= FVCO_MIN)
185 break;
186 ++res;
187 tmp <<= 1;
188 }
189 settings->ls_div_bits = res;
190 ls_freq = frequency << res;
191 }
192
193 /* Determine minimum HS_DIV, round up to even number */
194 settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
195
196 /* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
197 m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
198 do_div(m, FXO);
199 settings->m_frac = (u32)m & (BIT(29) - 1);
200 settings->m_int = (u32)(m >> 29);
201
202 return 0;
203 }
204
205 /* Calculate resulting frequency given the register settings */
si514_calc_rate(struct clk_si514_muldiv * settings)206 static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
207 {
208 u64 m = settings->m_frac | ((u64)settings->m_int << 29);
209 u32 d = settings->hs_div * BIT(settings->ls_div_bits);
210
211 return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
212 }
213
si514_recalc_rate(struct clk_hw * hw,unsigned long parent_rate)214 static unsigned long si514_recalc_rate(struct clk_hw *hw,
215 unsigned long parent_rate)
216 {
217 struct clk_si514 *data = to_clk_si514(hw);
218 struct clk_si514_muldiv settings;
219 int err;
220
221 err = si514_get_muldiv(data, &settings);
222 if (err) {
223 dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
224 return 0;
225 }
226
227 return si514_calc_rate(&settings);
228 }
229
si514_round_rate(struct clk_hw * hw,unsigned long rate,unsigned long * parent_rate)230 static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
231 unsigned long *parent_rate)
232 {
233 struct clk_si514_muldiv settings;
234 int err;
235
236 if (!rate)
237 return 0;
238
239 err = si514_calc_muldiv(&settings, rate);
240 if (err)
241 return err;
242
243 return si514_calc_rate(&settings);
244 }
245
246 /*
247 * Update output frequency for big frequency changes (> 1000 ppm).
248 * The chip supports <1000ppm changes "on the fly", we haven't implemented
249 * that here.
250 */
si514_set_rate(struct clk_hw * hw,unsigned long rate,unsigned long parent_rate)251 static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
252 unsigned long parent_rate)
253 {
254 struct clk_si514 *data = to_clk_si514(hw);
255 struct clk_si514_muldiv settings;
256 unsigned int old_oe_state;
257 int err;
258
259 err = si514_calc_muldiv(&settings, rate);
260 if (err)
261 return err;
262
263 err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
264 if (err)
265 return err;
266
267 si514_enable_output(data, false);
268
269 err = si514_set_muldiv(data, &settings);
270 if (err < 0)
271 return err; /* Undefined state now, best to leave disabled */
272
273 /* Trigger calibration */
274 err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
275 if (err < 0)
276 return err;
277
278 /* Applying a new frequency can take up to 10ms */
279 usleep_range(10000, 12000);
280
281 if (old_oe_state & SI514_CONTROL_OE)
282 si514_enable_output(data, true);
283
284 return err;
285 }
286
287 static const struct clk_ops si514_clk_ops = {
288 .prepare = si514_prepare,
289 .unprepare = si514_unprepare,
290 .is_prepared = si514_is_prepared,
291 .recalc_rate = si514_recalc_rate,
292 .round_rate = si514_round_rate,
293 .set_rate = si514_set_rate,
294 };
295
si514_regmap_is_volatile(struct device * dev,unsigned int reg)296 static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
297 {
298 switch (reg) {
299 case SI514_REG_CONTROL:
300 case SI514_REG_RESET:
301 return true;
302 default:
303 return false;
304 }
305 }
306
si514_regmap_is_writeable(struct device * dev,unsigned int reg)307 static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
308 {
309 switch (reg) {
310 case SI514_REG_LP:
311 case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
312 case SI514_REG_OE_STATE:
313 case SI514_REG_RESET:
314 case SI514_REG_CONTROL:
315 return true;
316 default:
317 return false;
318 }
319 }
320
321 static const struct regmap_config si514_regmap_config = {
322 .reg_bits = 8,
323 .val_bits = 8,
324 .cache_type = REGCACHE_RBTREE,
325 .max_register = SI514_REG_CONTROL,
326 .writeable_reg = si514_regmap_is_writeable,
327 .volatile_reg = si514_regmap_is_volatile,
328 };
329
si514_probe(struct i2c_client * client)330 static int si514_probe(struct i2c_client *client)
331 {
332 struct clk_si514 *data;
333 struct clk_init_data init;
334 int err;
335
336 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
337 if (!data)
338 return -ENOMEM;
339
340 init.ops = &si514_clk_ops;
341 init.flags = 0;
342 init.num_parents = 0;
343 data->hw.init = &init;
344 data->i2c_client = client;
345
346 if (of_property_read_string(client->dev.of_node, "clock-output-names",
347 &init.name))
348 init.name = client->dev.of_node->name;
349
350 data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
351 if (IS_ERR(data->regmap)) {
352 dev_err(&client->dev, "failed to allocate register map\n");
353 return PTR_ERR(data->regmap);
354 }
355
356 i2c_set_clientdata(client, data);
357
358 err = devm_clk_hw_register(&client->dev, &data->hw);
359 if (err) {
360 dev_err(&client->dev, "clock registration failed\n");
361 return err;
362 }
363 err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
364 &data->hw);
365 if (err) {
366 dev_err(&client->dev, "unable to add clk provider\n");
367 return err;
368 }
369
370 return 0;
371 }
372
373 static const struct i2c_device_id si514_id[] = {
374 { "si514", 0 },
375 { }
376 };
377 MODULE_DEVICE_TABLE(i2c, si514_id);
378
379 static const struct of_device_id clk_si514_of_match[] = {
380 { .compatible = "silabs,si514" },
381 { },
382 };
383 MODULE_DEVICE_TABLE(of, clk_si514_of_match);
384
385 static struct i2c_driver si514_driver = {
386 .driver = {
387 .name = "si514",
388 .of_match_table = clk_si514_of_match,
389 },
390 .probe = si514_probe,
391 .id_table = si514_id,
392 };
393 module_i2c_driver(si514_driver);
394
395 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
396 MODULE_DESCRIPTION("Si514 driver");
397 MODULE_LICENSE("GPL");
398