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Mike Looijmans8ce20e62015-10-02 09:15:29 +02001/*
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
77/* Retrieve clock multiplier and dividers from hardware */
78static int si514_get_muldiv(struct clk_si514 *data,
79 struct clk_si514_muldiv *settings)
80{
81 int err;
82 u8 reg[7];
83
84 err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
85 reg, ARRAY_SIZE(reg));
86 if (err)
87 return err;
88
89 settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
90 (reg[3] & 0x1F) << 24;
91 settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
92 settings->ls_div_bits = (reg[6] >> 4) & 0x07;
93 settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
94 return 0;
95}
96
97static int si514_set_muldiv(struct clk_si514 *data,
98 struct clk_si514_muldiv *settings)
99{
100 u8 lp;
101 u8 reg[7];
102 int err;
103
104 /* Calculate LP1/LP2 according to table 13 in the datasheet */
105 /* 65.259980246 */
106 if (settings->m_int < 65 ||
107 (settings->m_int == 65 && settings->m_frac <= 139575831))
108 lp = 0x22;
109 /* 67.859763463 */
110 else if (settings->m_int < 67 ||
111 (settings->m_int == 67 && settings->m_frac <= 461581994))
112 lp = 0x23;
113 /* 72.937624981 */
114 else if (settings->m_int < 72 ||
115 (settings->m_int == 72 && settings->m_frac <= 503383578))
116 lp = 0x33;
117 /* 75.843265046 */
118 else if (settings->m_int < 75 ||
119 (settings->m_int == 75 && settings->m_frac <= 452724474))
120 lp = 0x34;
121 else
122 lp = 0x44;
123
124 err = regmap_write(data->regmap, SI514_REG_LP, lp);
125 if (err < 0)
126 return err;
127
128 reg[0] = settings->m_frac;
129 reg[1] = settings->m_frac >> 8;
130 reg[2] = settings->m_frac >> 16;
131 reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
132 reg[4] = settings->m_int >> 3;
133 reg[5] = settings->hs_div;
134 reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
135
136 err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
137 if (err < 0)
138 return err;
139 /*
140 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
141 * must be written last
142 */
143 return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
144}
145
146/* Calculate divider settings for a given frequency */
147static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
148 unsigned long frequency)
149{
150 u64 m;
151 u32 ls_freq;
152 u32 tmp;
153 u8 res;
154
155 if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
156 return -EINVAL;
157
158 /* Determine the minimum value of LS_DIV and resulting target freq. */
159 ls_freq = frequency;
160 if (frequency >= (FVCO_MIN / HS_DIV_MAX))
161 settings->ls_div_bits = 0;
162 else {
163 res = 1;
164 tmp = 2 * HS_DIV_MAX;
165 while (tmp <= (HS_DIV_MAX * 32)) {
166 if ((frequency * tmp) >= FVCO_MIN)
167 break;
168 ++res;
169 tmp <<= 1;
170 }
171 settings->ls_div_bits = res;
172 ls_freq = frequency << res;
173 }
174
175 /* Determine minimum HS_DIV, round up to even number */
176 settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
177
178 /* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
179 m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
180 do_div(m, FXO);
181 settings->m_frac = (u32)m & (BIT(29) - 1);
182 settings->m_int = (u32)(m >> 29);
183
184 return 0;
185}
186
187/* Calculate resulting frequency given the register settings */
188static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
189{
190 u64 m = settings->m_frac | ((u64)settings->m_int << 29);
191 u32 d = settings->hs_div * BIT(settings->ls_div_bits);
192
193 return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
194}
195
196static unsigned long si514_recalc_rate(struct clk_hw *hw,
197 unsigned long parent_rate)
198{
199 struct clk_si514 *data = to_clk_si514(hw);
200 struct clk_si514_muldiv settings;
201 int err;
202
203 err = si514_get_muldiv(data, &settings);
204 if (err) {
205 dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
206 return 0;
207 }
208
209 return si514_calc_rate(&settings);
210}
211
212static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
213 unsigned long *parent_rate)
214{
215 struct clk_si514_muldiv settings;
216 int err;
217
218 if (!rate)
219 return 0;
220
221 err = si514_calc_muldiv(&settings, rate);
222 if (err)
223 return err;
224
225 return si514_calc_rate(&settings);
226}
227
228/*
229 * Update output frequency for big frequency changes (> 1000 ppm).
230 * The chip supports <1000ppm changes "on the fly", we haven't implemented
231 * that here.
232 */
233static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
234 unsigned long parent_rate)
235{
236 struct clk_si514 *data = to_clk_si514(hw);
237 struct clk_si514_muldiv settings;
238 int err;
239
240 err = si514_calc_muldiv(&settings, rate);
241 if (err)
242 return err;
243
244 si514_enable_output(data, false);
245
246 err = si514_set_muldiv(data, &settings);
247 if (err < 0)
248 return err; /* Undefined state now, best to leave disabled */
249
250 /* Trigger calibration */
251 err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
252 if (err < 0)
253 return err;
254
255 /* Applying a new frequency can take up to 10ms */
256 usleep_range(10000, 12000);
257
258 si514_enable_output(data, true);
259
260 return err;
261}
262
263static const struct clk_ops si514_clk_ops = {
264 .recalc_rate = si514_recalc_rate,
265 .round_rate = si514_round_rate,
266 .set_rate = si514_set_rate,
267};
268
269static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
270{
271 switch (reg) {
272 case SI514_REG_CONTROL:
273 case SI514_REG_RESET:
274 return true;
275 default:
276 return false;
277 }
278}
279
280static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
281{
282 switch (reg) {
283 case SI514_REG_LP:
284 case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
285 case SI514_REG_OE_STATE:
286 case SI514_REG_RESET:
287 case SI514_REG_CONTROL:
288 return true;
289 default:
290 return false;
291 }
292}
293
294static const struct regmap_config si514_regmap_config = {
295 .reg_bits = 8,
296 .val_bits = 8,
297 .cache_type = REGCACHE_RBTREE,
298 .max_register = SI514_REG_CONTROL,
299 .writeable_reg = si514_regmap_is_writeable,
300 .volatile_reg = si514_regmap_is_volatile,
301};
302
303static int si514_probe(struct i2c_client *client,
304 const struct i2c_device_id *id)
305{
306 struct clk_si514 *data;
307 struct clk_init_data init;
308 struct clk *clk;
309 int err;
310
311 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
312 if (!data)
313 return -ENOMEM;
314
315 init.ops = &si514_clk_ops;
316 init.flags = CLK_IS_ROOT;
317 init.num_parents = 0;
318 data->hw.init = &init;
319 data->i2c_client = client;
320
321 if (of_property_read_string(client->dev.of_node, "clock-output-names",
322 &init.name))
323 init.name = client->dev.of_node->name;
324
325 data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
326 if (IS_ERR(data->regmap)) {
327 dev_err(&client->dev, "failed to allocate register map\n");
328 return PTR_ERR(data->regmap);
329 }
330
331 i2c_set_clientdata(client, data);
332
333 clk = devm_clk_register(&client->dev, &data->hw);
334 if (IS_ERR(clk)) {
335 dev_err(&client->dev, "clock registration failed\n");
336 return PTR_ERR(clk);
337 }
338 err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
339 clk);
340 if (err) {
341 dev_err(&client->dev, "unable to add clk provider\n");
342 return err;
343 }
344
345 return 0;
346}
347
348static int si514_remove(struct i2c_client *client)
349{
350 of_clk_del_provider(client->dev.of_node);
351 return 0;
352}
353
354static const struct i2c_device_id si514_id[] = {
355 { "si514", 0 },
356 { }
357};
358MODULE_DEVICE_TABLE(i2c, si514_id);
359
360static const struct of_device_id clk_si514_of_match[] = {
361 { .compatible = "silabs,si514" },
362 { },
363};
364MODULE_DEVICE_TABLE(of, clk_si514_of_match);
365
366static struct i2c_driver si514_driver = {
367 .driver = {
368 .name = "si514",
369 .of_match_table = clk_si514_of_match,
370 },
371 .probe = si514_probe,
372 .remove = si514_remove,
373 .id_table = si514_id,
374};
375module_i2c_driver(si514_driver);
376
377MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
378MODULE_DESCRIPTION("Si514 driver");
379MODULE_LICENSE("GPL");