drivers/clk/clk-si570.c

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

DEFINITIONS
