drivers/clk/clk-si514.c

   1 /*
   2  * Driver for Silicon Labs Si514 Programmable Oscillator
   3  *
   4  * Copyright (C) 2015 Topic Embedded Products
   5  *
   6  * Author: Mike Looijmans <mike.looijmans@topic.nl>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #include <linux/clk-provider.h>
  20 #include <linux/delay.h>
  21 #include <linux/module.h>
  22 #include <linux/i2c.h>
  23 #include <linux/regmap.h>
  24 #include <linux/slab.h>
  25
  26 /* I2C registers */
  27 #define SI514_REG_LP            0
  28 #define SI514_REG_M_FRAC1       5
  29 #define SI514_REG_M_FRAC2       6
  30 #define SI514_REG_M_FRAC3       7
  31 #define SI514_REG_M_INT_FRAC    8
  32 #define SI514_REG_M_INT         9
  33 #define SI514_REG_HS_DIV        10
  34 #define SI514_REG_LS_HS_DIV     11
  35 #define SI514_REG_OE_STATE      14
  36 #define SI514_REG_RESET         128
  37 #define SI514_REG_CONTROL       132
  38
  39 /* Register values */
  40 #define SI514_RESET_RST         BIT(7)
  41
  42 #define SI514_CONTROL_FCAL      BIT(0)
  43 #define SI514_CONTROL_OE        BIT(2)
  44
  45 #define SI514_MIN_FREQ      100000U
  46 #define SI514_MAX_FREQ   250000000U
  47
  48 #define FXO               31980000U
  49
  50 #define FVCO_MIN        2080000000U
  51 #define FVCO_MAX        2500000000U
  52
  53 #define HS_DIV_MAX      1022
  54
  55 struct clk_si514 {
  56         struct clk_hw hw;
  57         struct regmap *regmap;
  58         struct i2c_client *i2c_client;
  59 };
  60 #define to_clk_si514(_hw)       container_of(_hw, struct clk_si514, hw)
  61
  62 /* Multiplier/divider settings */
  63 struct clk_si514_muldiv {
  64         u32 m_frac;  /* 29-bit Fractional part of multiplier M */
  65         u8 m_int; /* Integer part of multiplier M, 65..78 */
  66         u8 ls_div_bits; /* 2nd divider, as 2^x */
  67         u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
  68 };
  69
  70 /* Enables or disables the output driver */
  71 static int si514_enable_output(struct clk_si514 *data, bool enable)
  72 {
  73         return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
  74                 SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
  75 }
  76
  77 static int si514_prepare(struct clk_hw *hw)
  78 {
  79         struct clk_si514 *data = to_clk_si514(hw);
  80
  81         return si514_enable_output(data, true);
  82 }
  83
  84 static void si514_unprepare(struct clk_hw *hw)
  85 {
  86         struct clk_si514 *data = to_clk_si514(hw);
  87
  88         si514_enable_output(data, false);
  89 }
  90
  91 static int si514_is_prepared(struct clk_hw *hw)
  92 {
  93         struct clk_si514 *data = to_clk_si514(hw);
  94         unsigned int val;
  95         int err;
  96
  97         err = regmap_read(data->regmap, SI514_REG_CONTROL, &val);
  98         if (err < 0)
  99                 return err;
 100
 101         return !!(val & SI514_CONTROL_OE);
 102 }
 103
 104 /* Retrieve clock multiplier and dividers from hardware */
 105 static int si514_get_muldiv(struct clk_si514 *data,
 106         struct clk_si514_muldiv *settings)
 107 {
 108         int err;
 109         u8 reg[7];
 110
 111         err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
 112                         reg, ARRAY_SIZE(reg));
 113         if (err)
 114                 return err;
 115
 116         settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
 117                            (reg[3] & 0x1F) << 24;
 118         settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
 119         settings->ls_div_bits = (reg[6] >> 4) & 0x07;
 120         settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
 121         return 0;
 122 }
 123
 124 static int si514_set_muldiv(struct clk_si514 *data,
 125         struct clk_si514_muldiv *settings)
 126 {
 127         u8 lp;
 128         u8 reg[7];
 129         int err;
 130
 131         /* Calculate LP1/LP2 according to table 13 in the datasheet */
 132         /* 65.259980246 */
 133         if (settings->m_int < 65 ||
 134                 (settings->m_int == 65 && settings->m_frac <= 139575831))
 135                 lp = 0x22;
 136         /* 67.859763463 */
 137         else if (settings->m_int < 67 ||
 138                 (settings->m_int == 67 && settings->m_frac <= 461581994))
 139                 lp = 0x23;
 140         /* 72.937624981 */
 141         else if (settings->m_int < 72 ||
 142                 (settings->m_int == 72 && settings->m_frac <= 503383578))
 143                 lp = 0x33;
 144         /* 75.843265046 */
 145         else if (settings->m_int < 75 ||
 146                 (settings->m_int == 75 && settings->m_frac <= 452724474))
 147                 lp = 0x34;
 148         else
 149                 lp = 0x44;
 150
 151         err = regmap_write(data->regmap, SI514_REG_LP, lp);
 152         if (err < 0)
 153                 return err;
 154
 155         reg[0] = settings->m_frac;
 156         reg[1] = settings->m_frac >> 8;
 157         reg[2] = settings->m_frac >> 16;
 158         reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
 159         reg[4] = settings->m_int >> 3;
 160         reg[5] = settings->hs_div;
 161         reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
 162
 163         err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
 164         if (err < 0)
 165                 return err;
 166         /*
 167          * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
 168          * must be written last
 169          */
 170         return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
 171 }
 172
 173 /* Calculate divider settings for a given frequency */
 174 static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
 175         unsigned long frequency)
 176 {
 177         u64 m;
 178         u32 ls_freq;
 179         u32 tmp;
 180         u8 res;
 181
 182         if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
 183                 return -EINVAL;
 184
 185         /* Determine the minimum value of LS_DIV and resulting target freq. */
 186         ls_freq = frequency;
 187         if (frequency >= (FVCO_MIN / HS_DIV_MAX))
 188                 settings->ls_div_bits = 0;
 189         else {
 190                 res = 1;
 191                 tmp = 2 * HS_DIV_MAX;
 192                 while (tmp <= (HS_DIV_MAX * 32)) {
 193                         if ((frequency * tmp) >= FVCO_MIN)
 194                                 break;
 195                         ++res;
 196                         tmp <<= 1;
 197                 }
 198                 settings->ls_div_bits = res;
 199                 ls_freq = frequency << res;
 200         }
 201
 202         /* Determine minimum HS_DIV, round up to even number */
 203         settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
 204
 205         /* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
 206         m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
 207         do_div(m, FXO);
 208         settings->m_frac = (u32)m & (BIT(29) - 1);
 209         settings->m_int = (u32)(m >> 29);
 210
 211         return 0;
 212 }
 213
 214 /* Calculate resulting frequency given the register settings */
 215 static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
 216 {
 217         u64 m = settings->m_frac | ((u64)settings->m_int << 29);
 218         u32 d = settings->hs_div * BIT(settings->ls_div_bits);
 219
 220         return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
 221 }
 222
 223 static unsigned long si514_recalc_rate(struct clk_hw *hw,
 224                 unsigned long parent_rate)
 225 {
 226         struct clk_si514 *data = to_clk_si514(hw);
 227         struct clk_si514_muldiv settings;
 228         int err;
 229
 230         err = si514_get_muldiv(data, &settings);
 231         if (err) {
 232                 dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
 233                 return 0;
 234         }
 235
 236         return si514_calc_rate(&settings);
 237 }
 238
 239 static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
 240                 unsigned long *parent_rate)
 241 {
 242         struct clk_si514_muldiv settings;
 243         int err;
 244
 245         if (!rate)
 246                 return 0;
 247
 248         err = si514_calc_muldiv(&settings, rate);
 249         if (err)
 250                 return err;
 251
 252         return si514_calc_rate(&settings);
 253 }
 254
 255 /*
 256  * Update output frequency for big frequency changes (> 1000 ppm).
 257  * The chip supports <1000ppm changes "on the fly", we haven't implemented
 258  * that here.
 259  */
 260 static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
 261                 unsigned long parent_rate)
 262 {
 263         struct clk_si514 *data = to_clk_si514(hw);
 264         struct clk_si514_muldiv settings;
 265         unsigned int old_oe_state;
 266         int err;
 267
 268         err = si514_calc_muldiv(&settings, rate);
 269         if (err)
 270                 return err;
 271
 272         err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
 273         if (err)
 274                 return err;
 275
 276         si514_enable_output(data, false);
 277
 278         err = si514_set_muldiv(data, &settings);
 279         if (err < 0)
 280                 return err; /* Undefined state now, best to leave disabled */
 281
 282         /* Trigger calibration */
 283         err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
 284         if (err < 0)
 285                 return err;
 286
 287         /* Applying a new frequency can take up to 10ms */
 288         usleep_range(10000, 12000);
 289
 290         if (old_oe_state & SI514_CONTROL_OE)
 291                 si514_enable_output(data, true);
 292
 293         return err;
 294 }
 295
 296 static const struct clk_ops si514_clk_ops = {
 297         .prepare = si514_prepare,
 298         .unprepare = si514_unprepare,
 299         .is_prepared = si514_is_prepared,
 300         .recalc_rate = si514_recalc_rate,
 301         .round_rate = si514_round_rate,
 302         .set_rate = si514_set_rate,
 303 };
 304
 305 static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
 306 {
 307         switch (reg) {
 308         case SI514_REG_CONTROL:
 309         case SI514_REG_RESET:
 310                 return true;
 311         default:
 312                 return false;
 313         }
 314 }
 315
 316 static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
 317 {
 318         switch (reg) {
 319         case SI514_REG_LP:
 320         case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
 321         case SI514_REG_OE_STATE:
 322         case SI514_REG_RESET:
 323         case SI514_REG_CONTROL:
 324                 return true;
 325         default:
 326                 return false;
 327         }
 328 }
 329
 330 static const struct regmap_config si514_regmap_config = {
 331         .reg_bits = 8,
 332         .val_bits = 8,
 333         .cache_type = REGCACHE_RBTREE,
 334         .max_register = SI514_REG_CONTROL,
 335         .writeable_reg = si514_regmap_is_writeable,
 336         .volatile_reg = si514_regmap_is_volatile,
 337 };
 338
 339 static int si514_probe(struct i2c_client *client,
 340                 const struct i2c_device_id *id)
 341 {
 342         struct clk_si514 *data;
 343         struct clk_init_data init;
 344         int err;
 345
 346         data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 347         if (!data)
 348                 return -ENOMEM;
 349
 350         init.ops = &si514_clk_ops;
 351         init.flags = 0;
 352         init.num_parents = 0;
 353         data->hw.init = &init;
 354         data->i2c_client = client;
 355
 356         if (of_property_read_string(client->dev.of_node, "clock-output-names",
 357                         &init.name))
 358                 init.name = client->dev.of_node->name;
 359
 360         data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
 361         if (IS_ERR(data->regmap)) {
 362                 dev_err(&client->dev, "failed to allocate register map\n");
 363                 return PTR_ERR(data->regmap);
 364         }
 365
 366         i2c_set_clientdata(client, data);
 367
 368         err = devm_clk_hw_register(&client->dev, &data->hw);
 369         if (err) {
 370                 dev_err(&client->dev, "clock registration failed\n");
 371                 return err;
 372         }
 373         err = of_clk_add_hw_provider(client->dev.of_node, of_clk_hw_simple_get,
 374                                      &data->hw);
 375         if (err) {
 376                 dev_err(&client->dev, "unable to add clk provider\n");
 377                 return err;
 378         }
 379
 380         return 0;
 381 }
 382
 383 static int si514_remove(struct i2c_client *client)
 384 {
 385         of_clk_del_provider(client->dev.of_node);
 386         return 0;
 387 }
 388
 389 static const struct i2c_device_id si514_id[] = {
 390         { "si514", 0 },
 391         { }
 392 };
 393 MODULE_DEVICE_TABLE(i2c, si514_id);
 394
 395 static const struct of_device_id clk_si514_of_match[] = {
 396         { .compatible = "silabs,si514" },
 397         { },
 398 };
 399 MODULE_DEVICE_TABLE(of, clk_si514_of_match);
 400
 401 static struct i2c_driver si514_driver = {
 402         .driver = {
 403                 .name = "si514",
 404                 .of_match_table = clk_si514_of_match,
 405         },
 406         .probe          = si514_probe,
 407         .remove         = si514_remove,
 408         .id_table       = si514_id,
 409 };
 410 module_i2c_driver(si514_driver);
 411
 412 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
 413 MODULE_DESCRIPTION("Si514 driver");
 414 MODULE_LICENSE("GPL");