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-provider.h> 23 #include <linux/delay.h> 24 #include <linux/module.h> 25 #include <linux/i2c.h> 26 #include <linux/regmap.h> 27 #include <linux/slab.h> 28 29 /* Si570 registers */ 30 #define SI570_REG_HS_N1 7 31 #define SI570_REG_N1_RFREQ0 8 32 #define SI570_REG_RFREQ1 9 33 #define SI570_REG_RFREQ2 10 34 #define SI570_REG_RFREQ3 11 35 #define SI570_REG_RFREQ4 12 36 #define SI570_REG_CONTROL 135 37 #define SI570_REG_FREEZE_DCO 137 38 #define SI570_DIV_OFFSET_7PPM 6 39 40 #define HS_DIV_SHIFT 5 41 #define HS_DIV_MASK 0xe0 42 #define HS_DIV_OFFSET 4 43 #define N1_6_2_MASK 0x1f 44 #define N1_1_0_MASK 0xc0 45 #define RFREQ_37_32_MASK 0x3f 46 47 #define SI570_MIN_FREQ 10000000L 48 #define SI570_MAX_FREQ 1417500000L 49 #define SI598_MAX_FREQ 525000000L 50 51 #define FDCO_MIN 4850000000LL 52 #define FDCO_MAX 5670000000LL 53 54 #define SI570_CNTRL_RECALL (1 << 0) 55 #define SI570_CNTRL_FREEZE_M (1 << 5) 56 #define SI570_CNTRL_NEWFREQ (1 << 6) 57 58 #define SI570_FREEZE_DCO (1 << 4) 59 60 /** 61 * struct clk_si570: 62 * @hw: Clock hw struct 63 * @regmap: Device's regmap 64 * @div_offset: Rgister offset for dividers 65 * @max_freq: Maximum frequency for this device 66 * @fxtal: Factory xtal frequency 67 * @n1: Clock divider N1 68 * @hs_div: Clock divider HSDIV 69 * @rfreq: Clock multiplier RFREQ 70 * @frequency: Current output frequency 71 * @i2c_client: I2C client pointer 72 */ 73 struct clk_si570 { 74 struct clk_hw hw; 75 struct regmap *regmap; 76 unsigned int div_offset; 77 u64 max_freq; 78 u64 fxtal; 79 unsigned int n1; 80 unsigned int hs_div; 81 u64 rfreq; 82 u64 frequency; 83 struct i2c_client *i2c_client; 84 }; 85 #define to_clk_si570(_hw) container_of(_hw, struct clk_si570, hw) 86 87 enum clk_si570_variant { 88 si57x, 89 si59x 90 }; 91 92 /** 93 * si570_get_divs() - Read clock dividers from HW 94 * @data: Pointer to struct clk_si570 95 * @rfreq: Fractional multiplier (output) 96 * @n1: Divider N1 (output) 97 * @hs_div: Divider HSDIV (output) 98 * Returns 0 on success, negative errno otherwise. 99 * 100 * Retrieve clock dividers and multipliers from the HW. 101 */ 102 static int si570_get_divs(struct clk_si570 *data, u64 *rfreq, 103 unsigned int *n1, unsigned int *hs_div) 104 { 105 int err; 106 u8 reg[6]; 107 u64 tmp; 108 109 err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset, 110 reg, ARRAY_SIZE(reg)); 111 if (err) 112 return err; 113 114 *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET; 115 *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1; 116 /* Handle invalid cases */ 117 if (*n1 > 1) 118 *n1 &= ~1; 119 120 tmp = reg[1] & RFREQ_37_32_MASK; 121 tmp = (tmp << 8) + reg[2]; 122 tmp = (tmp << 8) + reg[3]; 123 tmp = (tmp << 8) + reg[4]; 124 tmp = (tmp << 8) + reg[5]; 125 *rfreq = tmp; 126 127 return 0; 128 } 129 130 /** 131 * si570_get_defaults() - Get default values 132 * @data: Driver data structure 133 * @fout: Factory frequency output 134 * Returns 0 on success, negative errno otherwise. 135 */ 136 static int si570_get_defaults(struct clk_si570 *data, u64 fout) 137 { 138 int err; 139 u64 fdco; 140 141 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL); 142 143 err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div); 144 if (err) 145 return err; 146 147 /* 148 * Accept optional precision loss to avoid arithmetic overflows. 149 * Acceptable per Silicon Labs Application Note AN334. 150 */ 151 fdco = fout * data->n1 * data->hs_div; 152 if (fdco >= (1LL << 36)) 153 data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4); 154 else 155 data->fxtal = div64_u64(fdco << 28, data->rfreq); 156 157 data->frequency = fout; 158 159 return 0; 160 } 161 162 /** 163 * si570_update_rfreq() - Update clock multiplier 164 * @data: Driver data structure 165 * Passes on regmap_bulk_write() return value. 166 */ 167 static int si570_update_rfreq(struct clk_si570 *data) 168 { 169 u8 reg[5]; 170 171 reg[0] = ((data->n1 - 1) << 6) | 172 ((data->rfreq >> 32) & RFREQ_37_32_MASK); 173 reg[1] = (data->rfreq >> 24) & 0xff; 174 reg[2] = (data->rfreq >> 16) & 0xff; 175 reg[3] = (data->rfreq >> 8) & 0xff; 176 reg[4] = data->rfreq & 0xff; 177 178 return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 + 179 data->div_offset, reg, ARRAY_SIZE(reg)); 180 } 181 182 /** 183 * si570_calc_divs() - Caluclate clock dividers 184 * @frequency: Target frequency 185 * @data: Driver data structure 186 * @out_rfreq: RFREG fractional multiplier (output) 187 * @out_n1: Clock divider N1 (output) 188 * @out_hs_div: Clock divider HSDIV (output) 189 * Returns 0 on success, negative errno otherwise. 190 * 191 * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier 192 * (@out_rfreq) for a given target @frequency. 193 */ 194 static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data, 195 u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div) 196 { 197 int i; 198 unsigned int n1, hs_div; 199 u64 fdco, best_fdco = ULLONG_MAX; 200 static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 }; 201 202 for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) { 203 hs_div = si570_hs_div_values[i]; 204 /* Calculate lowest possible value for n1 */ 205 n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency); 206 if (!n1 || (n1 & 1)) 207 n1++; 208 while (n1 <= 128) { 209 fdco = (u64)frequency * (u64)hs_div * (u64)n1; 210 if (fdco > FDCO_MAX) 211 break; 212 if (fdco >= FDCO_MIN && fdco < best_fdco) { 213 *out_n1 = n1; 214 *out_hs_div = hs_div; 215 *out_rfreq = div64_u64(fdco << 28, data->fxtal); 216 best_fdco = fdco; 217 } 218 n1 += (n1 == 1 ? 1 : 2); 219 } 220 } 221 222 if (best_fdco == ULLONG_MAX) 223 return -EINVAL; 224 225 return 0; 226 } 227 228 static unsigned long si570_recalc_rate(struct clk_hw *hw, 229 unsigned long parent_rate) 230 { 231 int err; 232 u64 rfreq, rate; 233 unsigned int n1, hs_div; 234 struct clk_si570 *data = to_clk_si570(hw); 235 236 err = si570_get_divs(data, &rfreq, &n1, &hs_div); 237 if (err) { 238 dev_err(&data->i2c_client->dev, "unable to recalc rate\n"); 239 return data->frequency; 240 } 241 242 rfreq = div_u64(rfreq, hs_div * n1); 243 rate = (data->fxtal * rfreq) >> 28; 244 245 return rate; 246 } 247 248 static long si570_round_rate(struct clk_hw *hw, unsigned long rate, 249 unsigned long *parent_rate) 250 { 251 int err; 252 u64 rfreq; 253 unsigned int n1, hs_div; 254 struct clk_si570 *data = to_clk_si570(hw); 255 256 if (!rate) 257 return 0; 258 259 if (div64_u64(abs(rate - data->frequency) * 10000LL, 260 data->frequency) < 35) { 261 rfreq = div64_u64((data->rfreq * rate) + 262 div64_u64(data->frequency, 2), data->frequency); 263 n1 = data->n1; 264 hs_div = data->hs_div; 265 266 } else { 267 err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div); 268 if (err) { 269 dev_err(&data->i2c_client->dev, 270 "unable to round rate\n"); 271 return 0; 272 } 273 } 274 275 return rate; 276 } 277 278 /** 279 * si570_set_frequency() - Adjust output frequency 280 * @data: Driver data structure 281 * @frequency: Target frequency 282 * Returns 0 on success. 283 * 284 * Update output frequency for big frequency changes (> 3,500 ppm). 285 */ 286 static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency) 287 { 288 int err; 289 290 err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1, 291 &data->hs_div); 292 if (err) 293 return err; 294 295 /* 296 * The DCO reg should be accessed with a read-modify-write operation 297 * per AN334 298 */ 299 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO); 300 regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset, 301 ((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) | 302 (((data->n1 - 1) >> 2) & N1_6_2_MASK)); 303 si570_update_rfreq(data); 304 regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0); 305 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ); 306 307 /* Applying a new frequency can take up to 10ms */ 308 usleep_range(10000, 12000); 309 310 return 0; 311 } 312 313 /** 314 * si570_set_frequency_small() - Adjust output frequency 315 * @data: Driver data structure 316 * @frequency: Target frequency 317 * Returns 0 on success. 318 * 319 * Update output frequency for small frequency changes (< 3,500 ppm). 320 */ 321 static int si570_set_frequency_small(struct clk_si570 *data, 322 unsigned long frequency) 323 { 324 /* 325 * This is a re-implementation of DIV_ROUND_CLOSEST 326 * using the div64_u64 function lieu of letting the compiler 327 * insert EABI calls 328 */ 329 data->rfreq = div64_u64((data->rfreq * frequency) + 330 div_u64(data->frequency, 2), data->frequency); 331 regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M); 332 si570_update_rfreq(data); 333 regmap_write(data->regmap, SI570_REG_CONTROL, 0); 334 335 /* Applying a new frequency (small change) can take up to 100us */ 336 usleep_range(100, 200); 337 338 return 0; 339 } 340 341 static int si570_set_rate(struct clk_hw *hw, unsigned long rate, 342 unsigned long parent_rate) 343 { 344 struct clk_si570 *data = to_clk_si570(hw); 345 struct i2c_client *client = data->i2c_client; 346 int err; 347 348 if (rate < SI570_MIN_FREQ || rate > data->max_freq) { 349 dev_err(&client->dev, 350 "requested frequency %lu Hz is out of range\n", rate); 351 return -EINVAL; 352 } 353 354 if (div64_u64(abs(rate - data->frequency) * 10000LL, 355 data->frequency) < 35) 356 err = si570_set_frequency_small(data, rate); 357 else 358 err = si570_set_frequency(data, rate); 359 360 if (err) 361 return err; 362 363 data->frequency = rate; 364 365 return 0; 366 } 367 368 static const struct clk_ops si570_clk_ops = { 369 .recalc_rate = si570_recalc_rate, 370 .round_rate = si570_round_rate, 371 .set_rate = si570_set_rate, 372 }; 373 374 static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg) 375 { 376 switch (reg) { 377 case SI570_REG_CONTROL: 378 return true; 379 default: 380 return false; 381 } 382 } 383 384 static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg) 385 { 386 switch (reg) { 387 case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM): 388 case SI570_REG_CONTROL: 389 case SI570_REG_FREEZE_DCO: 390 return true; 391 default: 392 return false; 393 } 394 } 395 396 static struct regmap_config si570_regmap_config = { 397 .reg_bits = 8, 398 .val_bits = 8, 399 .cache_type = REGCACHE_RBTREE, 400 .max_register = 137, 401 .writeable_reg = si570_regmap_is_writeable, 402 .volatile_reg = si570_regmap_is_volatile, 403 }; 404 405 static int si570_probe(struct i2c_client *client, 406 const struct i2c_device_id *id) 407 { 408 struct clk_si570 *data; 409 struct clk_init_data init; 410 struct clk *clk; 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 = CLK_IS_ROOT; 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 clk = devm_clk_register(&client->dev, &data->hw); 465 if (IS_ERR(clk)) { 466 dev_err(&client->dev, "clock registration failed\n"); 467 return PTR_ERR(clk); 468 } 469 err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get, 470 clk); 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(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