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 55 struct 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 */ 63 struct 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 */ 71 static 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 static 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 84 static 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 91 static 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 */ 105 static 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 } 123 124 static 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 */ 174 static 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 */ 215 static 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 } 222 223 static 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 } 238 239 static 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 */ 260 static 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 } 295 296 static 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 }; 304 305 static 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 } 315 316 static 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 } 329 330 static 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 }; 338 339 static 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 } 382 383 static int si514_remove(struct i2c_client *client) 384 { 385 of_clk_del_provider(client->dev.of_node); 386 return 0; 387 } 388 389 static const struct i2c_device_id si514_id[] = { 390 { "si514", 0 }, 391 { } 392 }; 393 MODULE_DEVICE_TABLE(i2c, si514_id); 394 395 static const struct of_device_id clk_si514_of_match[] = { 396 { .compatible = "silabs,si514" }, 397 { }, 398 }; 399 MODULE_DEVICE_TABLE(of, clk_si514_of_match); 400 401 static 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 }; 410 module_i2c_driver(si514_driver); 411 412 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>"); 413 MODULE_DESCRIPTION("Si514 driver"); 414 MODULE_LICENSE("GPL"); 415