1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Driver for Silicon Labs Si544 Programmable Oscillator 4 * Copyright (C) 2018 Topic Embedded Products 5 * Author: Mike Looijmans <mike.looijmans@topic.nl> 6 */ 7 8 #include <linux/clk-provider.h> 9 #include <linux/delay.h> 10 #include <linux/math64.h> 11 #include <linux/module.h> 12 #include <linux/i2c.h> 13 #include <linux/regmap.h> 14 #include <linux/slab.h> 15 16 /* I2C registers (decimal as in datasheet) */ 17 #define SI544_REG_CONTROL 7 18 #define SI544_REG_OE_STATE 17 19 #define SI544_REG_HS_DIV 23 20 #define SI544_REG_LS_HS_DIV 24 21 #define SI544_REG_FBDIV0 26 22 #define SI544_REG_FBDIV8 27 23 #define SI544_REG_FBDIV16 28 24 #define SI544_REG_FBDIV24 29 25 #define SI544_REG_FBDIV32 30 26 #define SI544_REG_FBDIV40 31 27 #define SI544_REG_FCAL_OVR 69 28 #define SI544_REG_ADPLL_DELTA_M0 231 29 #define SI544_REG_ADPLL_DELTA_M8 232 30 #define SI544_REG_ADPLL_DELTA_M16 233 31 #define SI544_REG_PAGE_SELECT 255 32 33 /* Register values */ 34 #define SI544_CONTROL_RESET BIT(7) 35 #define SI544_CONTROL_MS_ICAL2 BIT(3) 36 37 #define SI544_OE_STATE_ODC_OE BIT(0) 38 39 /* Max freq depends on speed grade */ 40 #define SI544_MIN_FREQ 200000U 41 42 /* Si544 Internal oscilator runs at 55.05 MHz */ 43 #define FXO 55050000U 44 45 /* VCO range is 10.8 .. 12.1 GHz, max depends on speed grade */ 46 #define FVCO_MIN 10800000000ULL 47 48 #define HS_DIV_MAX 2046 49 #define HS_DIV_MAX_ODD 33 50 51 /* Lowest frequency synthesizeable using only the HS divider */ 52 #define MIN_HSDIV_FREQ (FVCO_MIN / HS_DIV_MAX) 53 54 /* Range and interpretation of the adjustment value */ 55 #define DELTA_M_MAX 8161512 56 #define DELTA_M_FRAC_NUM 19 57 #define DELTA_M_FRAC_DEN 20000 58 59 enum si544_speed_grade { 60 si544a, 61 si544b, 62 si544c, 63 }; 64 65 struct clk_si544 { 66 struct clk_hw hw; 67 struct regmap *regmap; 68 struct i2c_client *i2c_client; 69 enum si544_speed_grade speed_grade; 70 }; 71 #define to_clk_si544(_hw) container_of(_hw, struct clk_si544, hw) 72 73 /** 74 * struct clk_si544_muldiv - Multiplier/divider settings 75 * @fb_div_frac: integer part of feedback divider (32 bits) 76 * @fb_div_int: fractional part of feedback divider (11 bits) 77 * @hs_div: 1st divider, 5..2046, must be even when >33 78 * @ls_div_bits: 2nd divider, as 2^x, range 0..5 79 * If ls_div_bits is non-zero, hs_div must be even 80 * @delta_m: Frequency shift for small -950..+950 ppm changes, 24 bit 81 */ 82 struct clk_si544_muldiv { 83 u32 fb_div_frac; 84 u16 fb_div_int; 85 u16 hs_div; 86 u8 ls_div_bits; 87 s32 delta_m; 88 }; 89 90 /* Enables or disables the output driver */ 91 static int si544_enable_output(struct clk_si544 *data, bool enable) 92 { 93 return regmap_update_bits(data->regmap, SI544_REG_OE_STATE, 94 SI544_OE_STATE_ODC_OE, enable ? SI544_OE_STATE_ODC_OE : 0); 95 } 96 97 static int si544_prepare(struct clk_hw *hw) 98 { 99 struct clk_si544 *data = to_clk_si544(hw); 100 101 return si544_enable_output(data, true); 102 } 103 104 static void si544_unprepare(struct clk_hw *hw) 105 { 106 struct clk_si544 *data = to_clk_si544(hw); 107 108 si544_enable_output(data, false); 109 } 110 111 static int si544_is_prepared(struct clk_hw *hw) 112 { 113 struct clk_si544 *data = to_clk_si544(hw); 114 unsigned int val; 115 int err; 116 117 err = regmap_read(data->regmap, SI544_REG_OE_STATE, &val); 118 if (err < 0) 119 return err; 120 121 return !!(val & SI544_OE_STATE_ODC_OE); 122 } 123 124 /* Retrieve clock multiplier and dividers from hardware */ 125 static int si544_get_muldiv(struct clk_si544 *data, 126 struct clk_si544_muldiv *settings) 127 { 128 int err; 129 u8 reg[6]; 130 131 err = regmap_bulk_read(data->regmap, SI544_REG_HS_DIV, reg, 2); 132 if (err) 133 return err; 134 135 settings->ls_div_bits = (reg[1] >> 4) & 0x07; 136 settings->hs_div = (reg[1] & 0x07) << 8 | reg[0]; 137 138 err = regmap_bulk_read(data->regmap, SI544_REG_FBDIV0, reg, 6); 139 if (err) 140 return err; 141 142 settings->fb_div_int = reg[4] | (reg[5] & 0x07) << 8; 143 settings->fb_div_frac = reg[0] | reg[1] << 8 | reg[2] << 16 | 144 reg[3] << 24; 145 146 err = regmap_bulk_read(data->regmap, SI544_REG_ADPLL_DELTA_M0, reg, 3); 147 if (err) 148 return err; 149 150 /* Interpret as 24-bit signed number */ 151 settings->delta_m = reg[0] << 8 | reg[1] << 16 | reg[2] << 24; 152 settings->delta_m >>= 8; 153 154 return 0; 155 } 156 157 static int si544_set_delta_m(struct clk_si544 *data, s32 delta_m) 158 { 159 u8 reg[3]; 160 161 reg[0] = delta_m; 162 reg[1] = delta_m >> 8; 163 reg[2] = delta_m >> 16; 164 165 return regmap_bulk_write(data->regmap, SI544_REG_ADPLL_DELTA_M0, 166 reg, 3); 167 } 168 169 static int si544_set_muldiv(struct clk_si544 *data, 170 struct clk_si544_muldiv *settings) 171 { 172 int err; 173 u8 reg[6]; 174 175 reg[0] = settings->hs_div; 176 reg[1] = settings->hs_div >> 8 | settings->ls_div_bits << 4; 177 178 err = regmap_bulk_write(data->regmap, SI544_REG_HS_DIV, reg, 2); 179 if (err < 0) 180 return err; 181 182 reg[0] = settings->fb_div_frac; 183 reg[1] = settings->fb_div_frac >> 8; 184 reg[2] = settings->fb_div_frac >> 16; 185 reg[3] = settings->fb_div_frac >> 24; 186 reg[4] = settings->fb_div_int; 187 reg[5] = settings->fb_div_int >> 8; 188 189 /* 190 * Writing to SI544_REG_FBDIV40 triggers the clock change, so that 191 * must be written last 192 */ 193 return regmap_bulk_write(data->regmap, SI544_REG_FBDIV0, reg, 6); 194 } 195 196 static bool is_valid_frequency(const struct clk_si544 *data, 197 unsigned long frequency) 198 { 199 unsigned long max_freq = 0; 200 201 if (frequency < SI544_MIN_FREQ) 202 return false; 203 204 switch (data->speed_grade) { 205 case si544a: 206 max_freq = 1500000000; 207 break; 208 case si544b: 209 max_freq = 800000000; 210 break; 211 case si544c: 212 max_freq = 350000000; 213 break; 214 } 215 216 return frequency <= max_freq; 217 } 218 219 /* Calculate divider settings for a given frequency */ 220 static int si544_calc_muldiv(struct clk_si544_muldiv *settings, 221 unsigned long frequency) 222 { 223 u64 vco; 224 u32 ls_freq; 225 u32 tmp; 226 u8 res; 227 228 /* Determine the minimum value of LS_DIV and resulting target freq. */ 229 ls_freq = frequency; 230 settings->ls_div_bits = 0; 231 232 if (frequency >= MIN_HSDIV_FREQ) { 233 settings->ls_div_bits = 0; 234 } else { 235 res = 1; 236 tmp = 2 * HS_DIV_MAX; 237 while (tmp <= (HS_DIV_MAX * 32)) { 238 if (((u64)frequency * tmp) >= FVCO_MIN) 239 break; 240 ++res; 241 tmp <<= 1; 242 } 243 settings->ls_div_bits = res; 244 ls_freq = frequency << res; 245 } 246 247 /* Determine minimum HS_DIV by rounding up */ 248 vco = FVCO_MIN + ls_freq - 1; 249 do_div(vco, ls_freq); 250 settings->hs_div = vco; 251 252 /* round up to even number when required */ 253 if ((settings->hs_div & 1) && 254 (settings->hs_div > HS_DIV_MAX_ODD || settings->ls_div_bits)) 255 ++settings->hs_div; 256 257 /* Calculate VCO frequency (in 10..12GHz range) */ 258 vco = (u64)ls_freq * settings->hs_div; 259 260 /* Calculate the integer part of the feedback divider */ 261 tmp = do_div(vco, FXO); 262 settings->fb_div_int = vco; 263 264 /* And the fractional bits using the remainder */ 265 vco = (u64)tmp << 32; 266 vco += FXO / 2; /* Round to nearest multiple */ 267 do_div(vco, FXO); 268 settings->fb_div_frac = vco; 269 270 /* Reset the frequency adjustment */ 271 settings->delta_m = 0; 272 273 return 0; 274 } 275 276 /* Calculate resulting frequency given the register settings */ 277 static unsigned long si544_calc_center_rate( 278 const struct clk_si544_muldiv *settings) 279 { 280 u32 d = settings->hs_div * BIT(settings->ls_div_bits); 281 u64 vco; 282 283 /* Calculate VCO from the fractional part */ 284 vco = (u64)settings->fb_div_frac * FXO; 285 vco += (FXO / 2); 286 vco >>= 32; 287 288 /* Add the integer part of the VCO frequency */ 289 vco += (u64)settings->fb_div_int * FXO; 290 291 /* Apply divider to obtain the generated frequency */ 292 do_div(vco, d); 293 294 return vco; 295 } 296 297 static unsigned long si544_calc_rate(const struct clk_si544_muldiv *settings) 298 { 299 unsigned long rate = si544_calc_center_rate(settings); 300 s64 delta = (s64)rate * (DELTA_M_FRAC_NUM * settings->delta_m); 301 302 /* 303 * The clock adjustment is much smaller than 1 Hz, round to the 304 * nearest multiple. Apparently div64_s64 rounds towards zero, hence 305 * check the sign and adjust into the proper direction. 306 */ 307 if (settings->delta_m < 0) 308 delta -= ((s64)DELTA_M_MAX * DELTA_M_FRAC_DEN) / 2; 309 else 310 delta += ((s64)DELTA_M_MAX * DELTA_M_FRAC_DEN) / 2; 311 delta = div64_s64(delta, ((s64)DELTA_M_MAX * DELTA_M_FRAC_DEN)); 312 313 return rate + delta; 314 } 315 316 static unsigned long si544_recalc_rate(struct clk_hw *hw, 317 unsigned long parent_rate) 318 { 319 struct clk_si544 *data = to_clk_si544(hw); 320 struct clk_si544_muldiv settings; 321 int err; 322 323 err = si544_get_muldiv(data, &settings); 324 if (err) 325 return 0; 326 327 return si544_calc_rate(&settings); 328 } 329 330 static long si544_round_rate(struct clk_hw *hw, unsigned long rate, 331 unsigned long *parent_rate) 332 { 333 struct clk_si544 *data = to_clk_si544(hw); 334 335 if (!is_valid_frequency(data, rate)) 336 return -EINVAL; 337 338 /* The accuracy is less than 1 Hz, so any rate is possible */ 339 return rate; 340 } 341 342 /* Calculates the maximum "small" change, 950 * rate / 1000000 */ 343 static unsigned long si544_max_delta(unsigned long rate) 344 { 345 u64 num = rate; 346 347 num *= DELTA_M_FRAC_NUM; 348 do_div(num, DELTA_M_FRAC_DEN); 349 350 return num; 351 } 352 353 static s32 si544_calc_delta(s32 delta, s32 max_delta) 354 { 355 s64 n = (s64)delta * DELTA_M_MAX; 356 357 return div_s64(n, max_delta); 358 } 359 360 static int si544_set_rate(struct clk_hw *hw, unsigned long rate, 361 unsigned long parent_rate) 362 { 363 struct clk_si544 *data = to_clk_si544(hw); 364 struct clk_si544_muldiv settings; 365 unsigned long center; 366 long max_delta; 367 long delta; 368 unsigned int old_oe_state; 369 int err; 370 371 if (!is_valid_frequency(data, rate)) 372 return -EINVAL; 373 374 /* Try using the frequency adjustment feature for a <= 950ppm change */ 375 err = si544_get_muldiv(data, &settings); 376 if (err) 377 return err; 378 379 center = si544_calc_center_rate(&settings); 380 max_delta = si544_max_delta(center); 381 delta = rate - center; 382 383 if (abs(delta) <= max_delta) 384 return si544_set_delta_m(data, 385 si544_calc_delta(delta, max_delta)); 386 387 /* Too big for the delta adjustment, need to reprogram */ 388 err = si544_calc_muldiv(&settings, rate); 389 if (err) 390 return err; 391 392 err = regmap_read(data->regmap, SI544_REG_OE_STATE, &old_oe_state); 393 if (err) 394 return err; 395 396 si544_enable_output(data, false); 397 398 /* Allow FCAL for this frequency update */ 399 err = regmap_write(data->regmap, SI544_REG_FCAL_OVR, 0); 400 if (err < 0) 401 return err; 402 403 err = si544_set_delta_m(data, settings.delta_m); 404 if (err < 0) 405 return err; 406 407 err = si544_set_muldiv(data, &settings); 408 if (err < 0) 409 return err; /* Undefined state now, best to leave disabled */ 410 411 /* Trigger calibration */ 412 err = regmap_write(data->regmap, SI544_REG_CONTROL, 413 SI544_CONTROL_MS_ICAL2); 414 if (err < 0) 415 return err; 416 417 /* Applying a new frequency can take up to 10ms */ 418 usleep_range(10000, 12000); 419 420 if (old_oe_state & SI544_OE_STATE_ODC_OE) 421 si544_enable_output(data, true); 422 423 return err; 424 } 425 426 static const struct clk_ops si544_clk_ops = { 427 .prepare = si544_prepare, 428 .unprepare = si544_unprepare, 429 .is_prepared = si544_is_prepared, 430 .recalc_rate = si544_recalc_rate, 431 .round_rate = si544_round_rate, 432 .set_rate = si544_set_rate, 433 }; 434 435 static bool si544_regmap_is_volatile(struct device *dev, unsigned int reg) 436 { 437 switch (reg) { 438 case SI544_REG_CONTROL: 439 case SI544_REG_FCAL_OVR: 440 return true; 441 default: 442 return false; 443 } 444 } 445 446 static const struct regmap_config si544_regmap_config = { 447 .reg_bits = 8, 448 .val_bits = 8, 449 .cache_type = REGCACHE_RBTREE, 450 .max_register = SI544_REG_PAGE_SELECT, 451 .volatile_reg = si544_regmap_is_volatile, 452 }; 453 454 static const struct i2c_device_id si544_id[] = { 455 { "si544a", si544a }, 456 { "si544b", si544b }, 457 { "si544c", si544c }, 458 { } 459 }; 460 MODULE_DEVICE_TABLE(i2c, si544_id); 461 462 static int si544_probe(struct i2c_client *client) 463 { 464 struct clk_si544 *data; 465 struct clk_init_data init; 466 const struct i2c_device_id *id = i2c_match_id(si544_id, client); 467 int err; 468 469 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL); 470 if (!data) 471 return -ENOMEM; 472 473 init.ops = &si544_clk_ops; 474 init.flags = 0; 475 init.num_parents = 0; 476 data->hw.init = &init; 477 data->i2c_client = client; 478 data->speed_grade = id->driver_data; 479 480 if (of_property_read_string(client->dev.of_node, "clock-output-names", 481 &init.name)) 482 init.name = client->dev.of_node->name; 483 484 data->regmap = devm_regmap_init_i2c(client, &si544_regmap_config); 485 if (IS_ERR(data->regmap)) 486 return PTR_ERR(data->regmap); 487 488 i2c_set_clientdata(client, data); 489 490 /* Select page 0, just to be sure, there appear to be no more */ 491 err = regmap_write(data->regmap, SI544_REG_PAGE_SELECT, 0); 492 if (err < 0) 493 return err; 494 495 err = devm_clk_hw_register(&client->dev, &data->hw); 496 if (err) { 497 dev_err(&client->dev, "clock registration failed\n"); 498 return err; 499 } 500 err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get, 501 &data->hw); 502 if (err) { 503 dev_err(&client->dev, "unable to add clk provider\n"); 504 return err; 505 } 506 507 return 0; 508 } 509 510 static const struct of_device_id clk_si544_of_match[] = { 511 { .compatible = "silabs,si544a" }, 512 { .compatible = "silabs,si544b" }, 513 { .compatible = "silabs,si544c" }, 514 { }, 515 }; 516 MODULE_DEVICE_TABLE(of, clk_si544_of_match); 517 518 static struct i2c_driver si544_driver = { 519 .driver = { 520 .name = "si544", 521 .of_match_table = clk_si544_of_match, 522 }, 523 .probe_new = si544_probe, 524 .id_table = si544_id, 525 }; 526 module_i2c_driver(si544_driver); 527 528 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>"); 529 MODULE_DESCRIPTION("Si544 driver"); 530 MODULE_LICENSE("GPL"); 531