1 /* 2 * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO 3 * 4 * Copyright (C) 2010, 2011 Ericsson AB. 5 * Copyright (C) 2011 Guenter Roeck. 6 * Copyright (C) 2011 - 2013 Xilinx Inc. 7 * 8 * Author: Guenter Roeck <guenter.roeck@ericsson.com> 9 * Sören Brinkmann <soren.brinkmann@xilinx.com> 10 * 11 * This program is free software; you can redistribute it and/or modify 12 * it under the terms of the GNU General Public License as published by 13 * the Free Software Foundation; either version 2 of the License, or 14 * (at your option) any later version. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 */ 21 22 #include <linux/clk.h> 23 #include <linux/clk-provider.h> 24 #include <linux/delay.h> 25 #include <linux/module.h> 26 #include <linux/i2c.h> 27 #include <linux/regmap.h> 28 #include <linux/slab.h> 29 30 /* Si570 registers */ 31 #define SI570_REG_HS_N1 7 32 #define SI570_REG_N1_RFREQ0 8 33 #define SI570_REG_RFREQ1 9 34 #define SI570_REG_RFREQ2 10 35 #define SI570_REG_RFREQ3 11 36 #define SI570_REG_RFREQ4 12 37 #define SI570_REG_CONTROL 135 38 #define SI570_REG_FREEZE_DCO 137 39 #define SI570_DIV_OFFSET_7PPM 6 40 41 #define HS_DIV_SHIFT 5 42 #define HS_DIV_MASK 0xe0 43 #define HS_DIV_OFFSET 4 44 #define N1_6_2_MASK 0x1f 45 #define N1_1_0_MASK 0xc0 46 #define RFREQ_37_32_MASK 0x3f 47 48 #define SI570_MIN_FREQ 10000000L 49 #define SI570_MAX_FREQ 1417500000L 50 #define SI598_MAX_FREQ 525000000L 51 52 #define FDCO_MIN 4850000000LL 53 #define FDCO_MAX 5670000000LL 54 55 #define SI570_CNTRL_RECALL (1 << 0) 56 #define SI570_CNTRL_FREEZE_M (1 << 5) 57 #define SI570_CNTRL_NEWFREQ (1 << 6) 58 59 #define SI570_FREEZE_DCO (1 << 4) 60 61 /** 62 * struct clk_si570: 63 * @hw: Clock hw struct 64 * @regmap: Device's regmap 65 * @div_offset: Rgister offset for dividers 66 * @max_freq: Maximum frequency for this device 67 * @fxtal: Factory xtal frequency 68 * @n1: Clock divider N1 69 * @hs_div: Clock divider HSDIV 70 * @rfreq: Clock multiplier RFREQ 71 * @frequency: Current output frequency 72 * @i2c_client: I2C client pointer 73 */ 74 struct clk_si570 { 75 struct clk_hw hw; 76 struct regmap *regmap; 77 unsigned int div_offset; 78 u64 max_freq; 79 u64 fxtal; 80 unsigned int n1; 81 unsigned int hs_div; 82 u64 rfreq; 83 u64 frequency; 84 struct i2c_client *i2c_client; 85 }; 86 #define to_clk_si570(_hw) container_of(_hw, struct clk_si570, hw) 87 88 enum clk_si570_variant { 89 si57x, 90 si59x 91 }; 92 93 /** 94 * si570_get_divs() - Read clock dividers from HW 95 * @data: Pointer to struct clk_si570 96 * @rfreq: Fractional multiplier (output) 97 * @n1: Divider N1 (output) 98 * @hs_div: Divider HSDIV (output) 99 * Returns 0 on success, negative errno otherwise. 100 * 101 * Retrieve clock dividers and multipliers from the HW. 102 */ 103 static int si570_get_divs(struct clk_si570 *data, u64 *rfreq, 104 unsigned int *n1, unsigned int *hs_div) 105 { 106 int err; 107 u8 reg[6]; 108 u64 tmp; 109 110 err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset, 111 reg, ARRAY_SIZE(reg)); 112 if (err) 113 return err; 114 115 *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET; 116 *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1; 117 /* Handle invalid cases */ 118 if (*n1 > 1) 119 *n1 &= ~1; 120 121 tmp = reg[1] & RFREQ_37_32_MASK; 122 tmp = (tmp << 8) + reg[2]; 123 tmp = (tmp << 8) + reg[3]; 124 tmp = (tmp << 8) + reg[4]; 125 tmp = (tmp << 8) + reg[5]; 126 *rfreq = tmp; 127 128 return 0; 129 } 130 131 /** 132 * si570_get_defaults() - Get default values 133 * @data: Driver data structure 134 * @fout: Factory frequency output 135 * Returns 0 on success, negative errno otherwise. 136 */ 137 static int si570_get_defaults(struct clk_si570 *data, u64 fout) 138 { 139 int err; 140 u64 fdco; 141 142 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL); 143 144 err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div); 145 if (err) 146 return err; 147 148 /* 149 * Accept optional precision loss to avoid arithmetic overflows. 150 * Acceptable per Silicon Labs Application Note AN334. 151 */ 152 fdco = fout * data->n1 * data->hs_div; 153 if (fdco >= (1LL << 36)) 154 data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4); 155 else 156 data->fxtal = div64_u64(fdco << 28, data->rfreq); 157 158 data->frequency = fout; 159 160 return 0; 161 } 162 163 /** 164 * si570_update_rfreq() - Update clock multiplier 165 * @data: Driver data structure 166 * Passes on regmap_bulk_write() return value. 167 */ 168 static int si570_update_rfreq(struct clk_si570 *data) 169 { 170 u8 reg[5]; 171 172 reg[0] = ((data->n1 - 1) << 6) | 173 ((data->rfreq >> 32) & RFREQ_37_32_MASK); 174 reg[1] = (data->rfreq >> 24) & 0xff; 175 reg[2] = (data->rfreq >> 16) & 0xff; 176 reg[3] = (data->rfreq >> 8) & 0xff; 177 reg[4] = data->rfreq & 0xff; 178 179 return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 + 180 data->div_offset, reg, ARRAY_SIZE(reg)); 181 } 182 183 /** 184 * si570_calc_divs() - Caluclate clock dividers 185 * @frequency: Target frequency 186 * @data: Driver data structure 187 * @out_rfreq: RFREG fractional multiplier (output) 188 * @out_n1: Clock divider N1 (output) 189 * @out_hs_div: Clock divider HSDIV (output) 190 * Returns 0 on success, negative errno otherwise. 191 * 192 * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier 193 * (@out_rfreq) for a given target @frequency. 194 */ 195 static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data, 196 u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div) 197 { 198 int i; 199 unsigned int n1, hs_div; 200 u64 fdco, best_fdco = ULLONG_MAX; 201 static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 }; 202 203 for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) { 204 hs_div = si570_hs_div_values[i]; 205 /* Calculate lowest possible value for n1 */ 206 n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency); 207 if (!n1 || (n1 & 1)) 208 n1++; 209 while (n1 <= 128) { 210 fdco = (u64)frequency * (u64)hs_div * (u64)n1; 211 if (fdco > FDCO_MAX) 212 break; 213 if (fdco >= FDCO_MIN && fdco < best_fdco) { 214 *out_n1 = n1; 215 *out_hs_div = hs_div; 216 *out_rfreq = div64_u64(fdco << 28, data->fxtal); 217 best_fdco = fdco; 218 } 219 n1 += (n1 == 1 ? 1 : 2); 220 } 221 } 222 223 if (best_fdco == ULLONG_MAX) 224 return -EINVAL; 225 226 return 0; 227 } 228 229 static unsigned long si570_recalc_rate(struct clk_hw *hw, 230 unsigned long parent_rate) 231 { 232 int err; 233 u64 rfreq, rate; 234 unsigned int n1, hs_div; 235 struct clk_si570 *data = to_clk_si570(hw); 236 237 err = si570_get_divs(data, &rfreq, &n1, &hs_div); 238 if (err) { 239 dev_err(&data->i2c_client->dev, "unable to recalc rate\n"); 240 return data->frequency; 241 } 242 243 rfreq = div_u64(rfreq, hs_div * n1); 244 rate = (data->fxtal * rfreq) >> 28; 245 246 return rate; 247 } 248 249 static long si570_round_rate(struct clk_hw *hw, unsigned long rate, 250 unsigned long *parent_rate) 251 { 252 int err; 253 u64 rfreq; 254 unsigned int n1, hs_div; 255 struct clk_si570 *data = to_clk_si570(hw); 256 257 if (!rate) 258 return 0; 259 260 if (div64_u64(abs(rate - data->frequency) * 10000LL, 261 data->frequency) < 35) { 262 rfreq = div64_u64((data->rfreq * rate) + 263 div64_u64(data->frequency, 2), data->frequency); 264 n1 = data->n1; 265 hs_div = data->hs_div; 266 267 } else { 268 err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div); 269 if (err) { 270 dev_err(&data->i2c_client->dev, 271 "unable to round rate\n"); 272 return 0; 273 } 274 } 275 276 return rate; 277 } 278 279 /** 280 * si570_set_frequency() - Adjust output frequency 281 * @data: Driver data structure 282 * @frequency: Target frequency 283 * Returns 0 on success. 284 * 285 * Update output frequency for big frequency changes (> 3,500 ppm). 286 */ 287 static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency) 288 { 289 int err; 290 291 err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1, 292 &data->hs_div); 293 if (err) 294 return err; 295 296 /* 297 * The DCO reg should be accessed with a read-modify-write operation 298 * per AN334 299 */ 300 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO); 301 regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset, 302 ((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) | 303 (((data->n1 - 1) >> 2) & N1_6_2_MASK)); 304 si570_update_rfreq(data); 305 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0); 306 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ); 307 308 /* Applying a new frequency can take up to 10ms */ 309 usleep_range(10000, 12000); 310 311 return 0; 312 } 313 314 /** 315 * si570_set_frequency_small() - Adjust output frequency 316 * @data: Driver data structure 317 * @frequency: Target frequency 318 * Returns 0 on success. 319 * 320 * Update output frequency for small frequency changes (< 3,500 ppm). 321 */ 322 static int si570_set_frequency_small(struct clk_si570 *data, 323 unsigned long frequency) 324 { 325 /* 326 * This is a re-implementation of DIV_ROUND_CLOSEST 327 * using the div64_u64 function lieu of letting the compiler 328 * insert EABI calls 329 */ 330 data->rfreq = div64_u64((data->rfreq * frequency) + 331 div_u64(data->frequency, 2), data->frequency); 332 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M); 333 si570_update_rfreq(data); 334 regmap_write(data->regmap, SI570_REG_CONTROL, 0); 335 336 /* Applying a new frequency (small change) can take up to 100us */ 337 usleep_range(100, 200); 338 339 return 0; 340 } 341 342 static int si570_set_rate(struct clk_hw *hw, unsigned long rate, 343 unsigned long parent_rate) 344 { 345 struct clk_si570 *data = to_clk_si570(hw); 346 struct i2c_client *client = data->i2c_client; 347 int err; 348 349 if (rate < SI570_MIN_FREQ || rate > data->max_freq) { 350 dev_err(&client->dev, 351 "requested frequency %lu Hz is out of range\n", rate); 352 return -EINVAL; 353 } 354 355 if (div64_u64(abs(rate - data->frequency) * 10000LL, 356 data->frequency) < 35) 357 err = si570_set_frequency_small(data, rate); 358 else 359 err = si570_set_frequency(data, rate); 360 361 if (err) 362 return err; 363 364 data->frequency = rate; 365 366 return 0; 367 } 368 369 static const struct clk_ops si570_clk_ops = { 370 .recalc_rate = si570_recalc_rate, 371 .round_rate = si570_round_rate, 372 .set_rate = si570_set_rate, 373 }; 374 375 static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg) 376 { 377 switch (reg) { 378 case SI570_REG_CONTROL: 379 return true; 380 default: 381 return false; 382 } 383 } 384 385 static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg) 386 { 387 switch (reg) { 388 case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM): 389 case SI570_REG_CONTROL: 390 case SI570_REG_FREEZE_DCO: 391 return true; 392 default: 393 return false; 394 } 395 } 396 397 static const struct regmap_config si570_regmap_config = { 398 .reg_bits = 8, 399 .val_bits = 8, 400 .cache_type = REGCACHE_RBTREE, 401 .max_register = 137, 402 .writeable_reg = si570_regmap_is_writeable, 403 .volatile_reg = si570_regmap_is_volatile, 404 }; 405 406 static int si570_probe(struct i2c_client *client, 407 const struct i2c_device_id *id) 408 { 409 struct clk_si570 *data; 410 struct clk_init_data init; 411 u32 initial_fout, factory_fout, stability; 412 int err; 413 enum clk_si570_variant variant = id->driver_data; 414 415 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL); 416 if (!data) 417 return -ENOMEM; 418 419 init.ops = &si570_clk_ops; 420 init.flags = 0; 421 init.num_parents = 0; 422 data->hw.init = &init; 423 data->i2c_client = client; 424 425 if (variant == si57x) { 426 err = of_property_read_u32(client->dev.of_node, 427 "temperature-stability", &stability); 428 if (err) { 429 dev_err(&client->dev, 430 "'temperature-stability' property missing\n"); 431 return err; 432 } 433 /* adjust register offsets for 7ppm devices */ 434 if (stability == 7) 435 data->div_offset = SI570_DIV_OFFSET_7PPM; 436 437 data->max_freq = SI570_MAX_FREQ; 438 } else { 439 data->max_freq = SI598_MAX_FREQ; 440 } 441 442 if (of_property_read_string(client->dev.of_node, "clock-output-names", 443 &init.name)) 444 init.name = client->dev.of_node->name; 445 446 err = of_property_read_u32(client->dev.of_node, "factory-fout", 447 &factory_fout); 448 if (err) { 449 dev_err(&client->dev, "'factory-fout' property missing\n"); 450 return err; 451 } 452 453 data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config); 454 if (IS_ERR(data->regmap)) { 455 dev_err(&client->dev, "failed to allocate register map\n"); 456 return PTR_ERR(data->regmap); 457 } 458 459 i2c_set_clientdata(client, data); 460 err = si570_get_defaults(data, factory_fout); 461 if (err) 462 return err; 463 464 err = devm_clk_hw_register(&client->dev, &data->hw); 465 if (err) { 466 dev_err(&client->dev, "clock registration failed\n"); 467 return err; 468 } 469 err = of_clk_add_hw_provider(client->dev.of_node, of_clk_hw_simple_get, 470 &data->hw); 471 if (err) { 472 dev_err(&client->dev, "unable to add clk provider\n"); 473 return err; 474 } 475 476 /* Read the requested initial output frequency from device tree */ 477 if (!of_property_read_u32(client->dev.of_node, "clock-frequency", 478 &initial_fout)) { 479 err = clk_set_rate(data->hw.clk, initial_fout); 480 if (err) { 481 of_clk_del_provider(client->dev.of_node); 482 return err; 483 } 484 } 485 486 /* Display a message indicating that we've successfully registered */ 487 dev_info(&client->dev, "registered, current frequency %llu Hz\n", 488 data->frequency); 489 490 return 0; 491 } 492 493 static int si570_remove(struct i2c_client *client) 494 { 495 of_clk_del_provider(client->dev.of_node); 496 return 0; 497 } 498 499 static const struct i2c_device_id si570_id[] = { 500 { "si570", si57x }, 501 { "si571", si57x }, 502 { "si598", si59x }, 503 { "si599", si59x }, 504 { } 505 }; 506 MODULE_DEVICE_TABLE(i2c, si570_id); 507 508 static const struct of_device_id clk_si570_of_match[] = { 509 { .compatible = "silabs,si570" }, 510 { .compatible = "silabs,si571" }, 511 { .compatible = "silabs,si598" }, 512 { .compatible = "silabs,si599" }, 513 { }, 514 }; 515 MODULE_DEVICE_TABLE(of, clk_si570_of_match); 516 517 static struct i2c_driver si570_driver = { 518 .driver = { 519 .name = "si570", 520 .of_match_table = clk_si570_of_match, 521 }, 522 .probe = si570_probe, 523 .remove = si570_remove, 524 .id_table = si570_id, 525 }; 526 module_i2c_driver(si570_driver); 527 528 MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>"); 529 MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>"); 530 MODULE_DESCRIPTION("Si570 driver"); 531 MODULE_LICENSE("GPL"); 532