1/*
2 * Driver for Silicon Labs Si514 Programmable Oscillator
3 *
4 * Copyright (C) 2015 Topic Embedded Products
5 *
6 * Author: Mike Looijmans <mike.looijmans@topic.nl>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 */
18
19#include <linux/clk-provider.h>
20#include <linux/delay.h>
21#include <linux/module.h>
22#include <linux/i2c.h>
23#include <linux/regmap.h>
24#include <linux/slab.h>
25
26/* I2C registers */
27#define SI514_REG_LP 0
28#define SI514_REG_M_FRAC1 5
29#define SI514_REG_M_FRAC2 6
30#define SI514_REG_M_FRAC3 7
31#define SI514_REG_M_INT_FRAC 8
32#define SI514_REG_M_INT 9
33#define SI514_REG_HS_DIV 10
34#define SI514_REG_LS_HS_DIV 11
35#define SI514_REG_OE_STATE 14
36#define SI514_REG_RESET 128
37#define SI514_REG_CONTROL 132
38
39/* Register values */
40#define SI514_RESET_RST BIT(7)
41
42#define SI514_CONTROL_FCAL BIT(0)
43#define SI514_CONTROL_OE BIT(2)
44
45#define SI514_MIN_FREQ 100000U
46#define SI514_MAX_FREQ 250000000U
47
48#define FXO 31980000U
49
50#define FVCO_MIN 2080000000U
51#define FVCO_MAX 2500000000U
52
53#define HS_DIV_MAX 1022
54
55struct clk_si514 {
56 struct clk_hw hw;
57 struct regmap *regmap;
58 struct i2c_client *i2c_client;
59};
60#define to_clk_si514(_hw) container_of(_hw, struct clk_si514, hw)
61
62/* Multiplier/divider settings */
63struct clk_si514_muldiv {
64 u32 m_frac; /* 29-bit Fractional part of multiplier M */
65 u8 m_int; /* Integer part of multiplier M, 65..78 */
66 u8 ls_div_bits; /* 2nd divider, as 2^x */
67 u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
68};
69
70/* Enables or disables the output driver */
71static int si514_enable_output(struct clk_si514 *data, bool enable)
72{
73 return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
74 SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
75}
76
77static int si514_prepare(struct clk_hw *hw)
78{
79 struct clk_si514 *data = to_clk_si514(hw);
80
81 return si514_enable_output(data, true);
82}
83
84static void si514_unprepare(struct clk_hw *hw)
85{
86 struct clk_si514 *data = to_clk_si514(hw);
87
88 si514_enable_output(data, false);
89}
90
91static int si514_is_prepared(struct clk_hw *hw)
92{
93 struct clk_si514 *data = to_clk_si514(hw);
94 unsigned int val;
95 int err;
96
97 err = regmap_read(data->regmap, SI514_REG_CONTROL, &val);
98 if (err < 0)
99 return err;
100
101 return !!(val & SI514_CONTROL_OE);
102}
103
104/* Retrieve clock multiplier and dividers from hardware */
105static int si514_get_muldiv(struct clk_si514 *data,
106 struct clk_si514_muldiv *settings)
107{
108 int err;
109 u8 reg[7];
110
111 err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
112 reg, ARRAY_SIZE(reg));
113 if (err)
114 return err;
115
116 settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
117 (reg[3] & 0x1F) << 24;
118 settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
119 settings->ls_div_bits = (reg[6] >> 4) & 0x07;
120 settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
121 return 0;
122}
123
124static int si514_set_muldiv(struct clk_si514 *data,
125 struct clk_si514_muldiv *settings)
126{
127 u8 lp;
128 u8 reg[7];
129 int err;
130
131 /* Calculate LP1/LP2 according to table 13 in the datasheet */
132 /* 65.259980246 */
133 if (settings->m_int < 65 ||
134 (settings->m_int == 65 && settings->m_frac <= 139575831))
135 lp = 0x22;
136 /* 67.859763463 */
137 else if (settings->m_int < 67 ||
138 (settings->m_int == 67 && settings->m_frac <= 461581994))
139 lp = 0x23;
140 /* 72.937624981 */
141 else if (settings->m_int < 72 ||
142 (settings->m_int == 72 && settings->m_frac <= 503383578))
143 lp = 0x33;
144 /* 75.843265046 */
145 else if (settings->m_int < 75 ||
146 (settings->m_int == 75 && settings->m_frac <= 452724474))
147 lp = 0x34;
148 else
149 lp = 0x44;
150
151 err = regmap_write(data->regmap, SI514_REG_LP, lp);
152 if (err < 0)
153 return err;
154
155 reg[0] = settings->m_frac;
156 reg[1] = settings->m_frac >> 8;
157 reg[2] = settings->m_frac >> 16;
158 reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
159 reg[4] = settings->m_int >> 3;
160 reg[5] = settings->hs_div;
161 reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
162
163 err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
164 if (err < 0)
165 return err;
166 /*
167 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
168 * must be written last
169 */
170 return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
171}
172
173/* Calculate divider settings for a given frequency */
174static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
175 unsigned long frequency)
176{
177 u64 m;
178 u32 ls_freq;
179 u32 tmp;
180 u8 res;
181
182 if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
183 return -EINVAL;
184
185 /* Determine the minimum value of LS_DIV and resulting target freq. */
186 ls_freq = frequency;
187 if (frequency >= (FVCO_MIN / HS_DIV_MAX))
188 settings->ls_div_bits = 0;
189 else {
190 res = 1;
191 tmp = 2 * HS_DIV_MAX;
192 while (tmp <= (HS_DIV_MAX * 32)) {
193 if ((frequency * tmp) >= FVCO_MIN)
194 break;
195 ++res;
196 tmp <<= 1;
197 }
198 settings->ls_div_bits = res;
199 ls_freq = frequency << res;
200 }
201
202 /* Determine minimum HS_DIV, round up to even number */
203 settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
204
205 /* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
206 m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
207 do_div(m, FXO);
208 settings->m_frac = (u32)m & (BIT(29) - 1);
209 settings->m_int = (u32)(m >> 29);
210
211 return 0;
212}
213
214/* Calculate resulting frequency given the register settings */
215static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
216{
217 u64 m = settings->m_frac | ((u64)settings->m_int << 29);
218 u32 d = settings->hs_div * BIT(settings->ls_div_bits);
219
220 return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
221}
222
223static unsigned long si514_recalc_rate(struct clk_hw *hw,
224 unsigned long parent_rate)
225{
226 struct clk_si514 *data = to_clk_si514(hw);
227 struct clk_si514_muldiv settings;
228 int err;
229
230 err = si514_get_muldiv(data, &settings);
231 if (err) {
232 dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
233 return 0;
234 }
235
236 return si514_calc_rate(&settings);
237}
238
239static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
240 unsigned long *parent_rate)
241{
242 struct clk_si514_muldiv settings;
243 int err;
244
245 if (!rate)
246 return 0;
247
248 err = si514_calc_muldiv(&settings, rate);
249 if (err)
250 return err;
251
252 return si514_calc_rate(&settings);
253}
254
255/*
256 * Update output frequency for big frequency changes (> 1000 ppm).
257 * The chip supports <1000ppm changes "on the fly", we haven't implemented
258 * that here.
259 */
260static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
261 unsigned long parent_rate)
262{
263 struct clk_si514 *data = to_clk_si514(hw);
264 struct clk_si514_muldiv settings;
265 unsigned int old_oe_state;
266 int err;
267
268 err = si514_calc_muldiv(&settings, rate);
269 if (err)
270 return err;
271
272 err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
273 if (err)
274 return err;
275
276 si514_enable_output(data, false);
277
278 err = si514_set_muldiv(data, &settings);
279 if (err < 0)
280 return err; /* Undefined state now, best to leave disabled */
281
282 /* Trigger calibration */
283 err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
284 if (err < 0)
285 return err;
286
287 /* Applying a new frequency can take up to 10ms */
288 usleep_range(10000, 12000);
289
290 if (old_oe_state & SI514_CONTROL_OE)
291 si514_enable_output(data, true);
292
293 return err;
294}
295
296static const struct clk_ops si514_clk_ops = {
297 .prepare = si514_prepare,
298 .unprepare = si514_unprepare,
299 .is_prepared = si514_is_prepared,
300 .recalc_rate = si514_recalc_rate,
301 .round_rate = si514_round_rate,
302 .set_rate = si514_set_rate,
303};
304
305static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
306{
307 switch (reg) {
308 case SI514_REG_CONTROL:
309 case SI514_REG_RESET:
310 return true;
311 default:
312 return false;
313 }
314}
315
316static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
317{
318 switch (reg) {
319 case SI514_REG_LP:
320 case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
321 case SI514_REG_OE_STATE:
322 case SI514_REG_RESET:
323 case SI514_REG_CONTROL:
324 return true;
325 default:
326 return false;
327 }
328}
329
330static const struct regmap_config si514_regmap_config = {
331 .reg_bits = 8,
332 .val_bits = 8,
333 .cache_type = REGCACHE_RBTREE,
334 .max_register = SI514_REG_CONTROL,
335 .writeable_reg = si514_regmap_is_writeable,
336 .volatile_reg = si514_regmap_is_volatile,
337};
338
339static int si514_probe(struct i2c_client *client,
340 const struct i2c_device_id *id)
341{
342 struct clk_si514 *data;
343 struct clk_init_data init;
344 int err;
345
346 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
347 if (!data)
348 return -ENOMEM;
349
350 init.ops = &si514_clk_ops;
351 init.flags = 0;
352 init.num_parents = 0;
353 data->hw.init = &init;
354 data->i2c_client = client;
355
356 if (of_property_read_string(client->dev.of_node, "clock-output-names",
357 &init.name))
358 init.name = client->dev.of_node->name;
359
360 data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
361 if (IS_ERR(data->regmap)) {
362 dev_err(&client->dev, "failed to allocate register map\n");
363 return PTR_ERR(data->regmap);
364 }
365
366 i2c_set_clientdata(client, data);
367
368 err = devm_clk_hw_register(&client->dev, &data->hw);
369 if (err) {
370 dev_err(&client->dev, "clock registration failed\n");
371 return err;
372 }
373 err = of_clk_add_hw_provider(client->dev.of_node, of_clk_hw_simple_get,
374 &data->hw);
375 if (err) {
376 dev_err(&client->dev, "unable to add clk provider\n");
377 return err;
378 }
379
380 return 0;
381}
382
383static int si514_remove(struct i2c_client *client)
384{
385 of_clk_del_provider(client->dev.of_node);
386 return 0;
387}
388
389static const struct i2c_device_id si514_id[] = {
390 { "si514", 0 },
391 { }
392};
393MODULE_DEVICE_TABLE(i2c, si514_id);
394
395static const struct of_device_id clk_si514_of_match[] = {
396 { .compatible = "silabs,si514" },
397 { },
398};
399MODULE_DEVICE_TABLE(of, clk_si514_of_match);
400
401static struct i2c_driver si514_driver = {
402 .driver = {
403 .name = "si514",
404 .of_match_table = clk_si514_of_match,
405 },
406 .probe = si514_probe,
407 .remove = si514_remove,
408 .id_table = si514_id,
409};
410module_i2c_driver(si514_driver);
411
412MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
413MODULE_DESCRIPTION("Si514 driver");
414MODULE_LICENSE("GPL");
415