drivers/clk/clk-si570.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
   4  *
   5  * Copyright (C) 2010, 2011 Ericsson AB.
   6  * Copyright (C) 2011 Guenter Roeck.
   7  * Copyright (C) 2011 - 2021 Xilinx Inc.
   8  *
   9  * Author: Guenter Roeck <guenter.roeck@ericsson.com>
  10  *         Sören Brinkmann <soren.brinkmann@xilinx.com>
  11  */
  12
  13 #include <linux/clk.h>
  14 #include <linux/clk-provider.h>
  15 #include <linux/delay.h>
  16 #include <linux/module.h>
  17 #include <linux/i2c.h>
  18 #include <linux/regmap.h>
  19 #include <linux/slab.h>
  20
  21 /* Si570 registers */
  22 #define SI570_REG_HS_N1         7
  23 #define SI570_REG_N1_RFREQ0     8
  24 #define SI570_REG_RFREQ1        9
  25 #define SI570_REG_RFREQ2        10
  26 #define SI570_REG_RFREQ3        11
  27 #define SI570_REG_RFREQ4        12
  28 #define SI570_REG_CONTROL       135
  29 #define SI570_REG_FREEZE_DCO    137
  30 #define SI570_DIV_OFFSET_7PPM   6
  31
  32 #define HS_DIV_SHIFT            5
  33 #define HS_DIV_MASK             0xe0
  34 #define HS_DIV_OFFSET           4
  35 #define N1_6_2_MASK             0x1f
  36 #define N1_1_0_MASK             0xc0
  37 #define RFREQ_37_32_MASK        0x3f
  38
  39 #define SI570_MIN_FREQ          10000000L
  40 #define SI570_MAX_FREQ          1417500000L
  41 #define SI598_MAX_FREQ          525000000L
  42
  43 #define FDCO_MIN                4850000000LL
  44 #define FDCO_MAX                5670000000LL
  45
  46 #define SI570_CNTRL_RECALL      (1 << 0)
  47 #define SI570_CNTRL_FREEZE_M    (1 << 5)
  48 #define SI570_CNTRL_NEWFREQ     (1 << 6)
  49
  50 #define SI570_FREEZE_DCO        (1 << 4)
  51
  52 /**
  53  * struct clk_si570_info:
  54  * @max_freq:   Maximum frequency for this device
  55  * @has_temperature_stability: Device support temperature stability
  56  */
  57 struct clk_si570_info {
  58         u64 max_freq;
  59         bool has_temperature_stability;
  60 };
  61
  62 /**
  63  * struct clk_si570:
  64  * @hw: Clock hw struct
  65  * @regmap:     Device's regmap
  66  * @div_offset: Rgister offset for dividers
  67  * @info:       Device info
  68  * @fxtal:      Factory xtal frequency
  69  * @n1:         Clock divider N1
  70  * @hs_div:     Clock divider HSDIV
  71  * @rfreq:      Clock multiplier RFREQ
  72  * @frequency:  Current output frequency
  73  * @i2c_client: I2C client pointer
  74  */
  75 struct clk_si570 {
  76         struct clk_hw hw;
  77         struct regmap *regmap;
  78         unsigned int div_offset;
  79         const struct clk_si570_info *info;
  80         u64 fxtal;
  81         unsigned int n1;
  82         unsigned int hs_div;
  83         u64 rfreq;
  84         u64 frequency;
  85         struct i2c_client *i2c_client;
  86 };
  87 #define to_clk_si570(_hw)       container_of(_hw, struct clk_si570, hw)
  88
  89 /**
  90  * si570_get_divs() - Read clock dividers from HW
  91  * @data:       Pointer to struct clk_si570
  92  * @rfreq:      Fractional multiplier (output)
  93  * @n1:         Divider N1 (output)
  94  * @hs_div:     Divider HSDIV (output)
  95  * Returns 0 on success, negative errno otherwise.
  96  *
  97  * Retrieve clock dividers and multipliers from the HW.
  98  */
  99 static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
 100                 unsigned int *n1, unsigned int *hs_div)
 101 {
 102         int err;
 103         u8 reg[6];
 104         u64 tmp;
 105
 106         err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
 107                         reg, ARRAY_SIZE(reg));
 108         if (err)
 109                 return err;
 110
 111         *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
 112         *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
 113         /* Handle invalid cases */
 114         if (*n1 > 1)
 115                 *n1 &= ~1;
 116
 117         tmp = reg[1] & RFREQ_37_32_MASK;
 118         tmp = (tmp << 8) + reg[2];
 119         tmp = (tmp << 8) + reg[3];
 120         tmp = (tmp << 8) + reg[4];
 121         tmp = (tmp << 8) + reg[5];
 122         *rfreq = tmp;
 123
 124         return 0;
 125 }
 126
 127 /**
 128  * si570_get_defaults() - Get default values
 129  * @data:       Driver data structure
 130  * @fout:       Factory frequency output
 131  * @skip_recall:        If true, don't recall NVM into RAM
 132  * Returns 0 on success, negative errno otherwise.
 133  */
 134 static int si570_get_defaults(struct clk_si570 *data, u64 fout,
 135                               bool skip_recall)
 136 {
 137         int err;
 138         u64 fdco;
 139
 140         if (!skip_recall)
 141                 regmap_write(data->regmap, SI570_REG_CONTROL,
 142                              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->info->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_MAPLE,
 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 {
 408         struct clk_si570 *data;
 409         struct clk_init_data init;
 410         u32 initial_fout, factory_fout, stability;
 411         bool skip_recall;
 412         int err;
 413
 414         data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 415         if (!data)
 416                 return -ENOMEM;
 417
 418         init.ops = &si570_clk_ops;
 419         init.flags = 0;
 420         init.num_parents = 0;
 421         data->hw.init = &init;
 422         data->i2c_client = client;
 423
 424         data->info = i2c_get_match_data(client);
 425         if (data->info->has_temperature_stability) {
 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
 438         if (of_property_read_string(client->dev.of_node, "clock-output-names",
 439                         &init.name))
 440                 init.name = client->dev.of_node->name;
 441
 442         err = of_property_read_u32(client->dev.of_node, "factory-fout",
 443                         &factory_fout);
 444         if (err) {
 445                 dev_err(&client->dev, "'factory-fout' property missing\n");
 446                 return err;
 447         }
 448
 449         skip_recall = of_property_read_bool(client->dev.of_node,
 450                                             "silabs,skip-recall");
 451
 452         data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
 453         if (IS_ERR(data->regmap)) {
 454                 dev_err(&client->dev, "failed to allocate register map\n");
 455                 return PTR_ERR(data->regmap);
 456         }
 457
 458         i2c_set_clientdata(client, data);
 459         err = si570_get_defaults(data, factory_fout, skip_recall);
 460         if (err)
 461                 return err;
 462
 463         err = devm_clk_hw_register(&client->dev, &data->hw);
 464         if (err) {
 465                 dev_err(&client->dev, "clock registration failed\n");
 466                 return err;
 467         }
 468         err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
 469                                           &data->hw);
 470         if (err) {
 471                 dev_err(&client->dev, "unable to add clk provider\n");
 472                 return err;
 473         }
 474
 475         /* Read the requested initial output frequency from device tree */
 476         if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
 477                                 &initial_fout)) {
 478                 err = clk_set_rate(data->hw.clk, initial_fout);
 479                 if (err)
 480                         return err;
 481         }
 482
 483         /* Display a message indicating that we've successfully registered */
 484         dev_info(&client->dev, "registered, current frequency %llu Hz\n",
 485                         data->frequency);
 486
 487         return 0;
 488 }
 489
 490 static const struct clk_si570_info clk_si570_info = {
 491         .max_freq = SI570_MAX_FREQ,
 492         .has_temperature_stability = true,
 493 };
 494
 495 static const struct clk_si570_info clk_si590_info = {
 496         .max_freq = SI598_MAX_FREQ,
 497 };
 498
 499 static const struct i2c_device_id si570_id[] = {
 500         { "si570", (kernel_ulong_t)&clk_si570_info },
 501         { "si571", (kernel_ulong_t)&clk_si570_info },
 502         { "si598", (kernel_ulong_t)&clk_si590_info },
 503         { "si599", (kernel_ulong_t)&clk_si590_info },
 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", .data = &clk_si570_info },
 510         { .compatible = "silabs,si571", .data = &clk_si570_info },
 511         { .compatible = "silabs,si598", .data = &clk_si590_info },
 512         { .compatible = "silabs,si599", .data = &clk_si590_info },
 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         .id_table       = si570_id,
 524 };
 525 module_i2c_driver(si570_driver);
 526
 527 MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
 528 MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
 529 MODULE_DESCRIPTION("Si570 driver");
 530 MODULE_LICENSE("GPL");