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 /* Retrieve clock multiplier and dividers from hardware */
  78 static int si514_get_muldiv(struct clk_si514 *data,
  79         struct clk_si514_muldiv *settings)
  80 {
  81         int err;
  82         u8 reg[7];
  83
  84         err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
  85                         reg, ARRAY_SIZE(reg));
  86         if (err)
  87                 return err;
  88
  89         settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
  90                            (reg[3] & 0x1F) << 24;
  91         settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
  92         settings->ls_div_bits = (reg[6] >> 4) & 0x07;
  93         settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
  94         return 0;
  95 }
  96
  97 static int si514_set_muldiv(struct clk_si514 *data,
  98         struct clk_si514_muldiv *settings)
  99 {
 100         u8 lp;
 101         u8 reg[7];
 102         int err;
 103
 104         /* Calculate LP1/LP2 according to table 13 in the datasheet */
 105         /* 65.259980246 */
 106         if (settings->m_int < 65 ||
 107                 (settings->m_int == 65 && settings->m_frac <= 139575831))
 108                 lp = 0x22;
 109         /* 67.859763463 */
 110         else if (settings->m_int < 67 ||
 111                 (settings->m_int == 67 && settings->m_frac <= 461581994))
 112                 lp = 0x23;
 113         /* 72.937624981 */
 114         else if (settings->m_int < 72 ||
 115                 (settings->m_int == 72 && settings->m_frac <= 503383578))
 116                 lp = 0x33;
 117         /* 75.843265046 */
 118         else if (settings->m_int < 75 ||
 119                 (settings->m_int == 75 && settings->m_frac <= 452724474))
 120                 lp = 0x34;
 121         else
 122                 lp = 0x44;
 123
 124         err = regmap_write(data->regmap, SI514_REG_LP, lp);
 125         if (err < 0)
 126                 return err;
 127
 128         reg[0] = settings->m_frac;
 129         reg[1] = settings->m_frac >> 8;
 130         reg[2] = settings->m_frac >> 16;
 131         reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
 132         reg[4] = settings->m_int >> 3;
 133         reg[5] = settings->hs_div;
 134         reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
 135
 136         err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
 137         if (err < 0)
 138                 return err;
 139         /*
 140          * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
 141          * must be written last
 142          */
 143         return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
 144 }
 145
 146 /* Calculate divider settings for a given frequency */
 147 static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
 148         unsigned long frequency)
 149 {
 150         u64 m;
 151         u32 ls_freq;
 152         u32 tmp;
 153         u8 res;
 154
 155         if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
 156                 return -EINVAL;
 157
 158         /* Determine the minimum value of LS_DIV and resulting target freq. */
 159         ls_freq = frequency;
 160         if (frequency >= (FVCO_MIN / HS_DIV_MAX))
 161                 settings->ls_div_bits = 0;
 162         else {
 163                 res = 1;
 164                 tmp = 2 * HS_DIV_MAX;
 165                 while (tmp <= (HS_DIV_MAX * 32)) {
 166                         if ((frequency * tmp) >= FVCO_MIN)
 167                                 break;
 168                         ++res;
 169                         tmp <<= 1;
 170                 }
 171                 settings->ls_div_bits = res;
 172                 ls_freq = frequency << res;
 173         }
 174
 175         /* Determine minimum HS_DIV, round up to even number */
 176         settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
 177
 178         /* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
 179         m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
 180         do_div(m, FXO);
 181         settings->m_frac = (u32)m & (BIT(29) - 1);
 182         settings->m_int = (u32)(m >> 29);
 183
 184         return 0;
 185 }
 186
 187 /* Calculate resulting frequency given the register settings */
 188 static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
 189 {
 190         u64 m = settings->m_frac | ((u64)settings->m_int << 29);
 191         u32 d = settings->hs_div * BIT(settings->ls_div_bits);
 192
 193         return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
 194 }
 195
 196 static unsigned long si514_recalc_rate(struct clk_hw *hw,
 197                 unsigned long parent_rate)
 198 {
 199         struct clk_si514 *data = to_clk_si514(hw);
 200         struct clk_si514_muldiv settings;
 201         int err;
 202
 203         err = si514_get_muldiv(data, &settings);
 204         if (err) {
 205                 dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
 206                 return 0;
 207         }
 208
 209         return si514_calc_rate(&settings);
 210 }
 211
 212 static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
 213                 unsigned long *parent_rate)
 214 {
 215         struct clk_si514_muldiv settings;
 216         int err;
 217
 218         if (!rate)
 219                 return 0;
 220
 221         err = si514_calc_muldiv(&settings, rate);
 222         if (err)
 223                 return err;
 224
 225         return si514_calc_rate(&settings);
 226 }
 227
 228 /*
 229  * Update output frequency for big frequency changes (> 1000 ppm).
 230  * The chip supports <1000ppm changes "on the fly", we haven't implemented
 231  * that here.
 232  */
 233 static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
 234                 unsigned long parent_rate)
 235 {
 236         struct clk_si514 *data = to_clk_si514(hw);
 237         struct clk_si514_muldiv settings;
 238         int err;
 239
 240         err = si514_calc_muldiv(&settings, rate);
 241         if (err)
 242                 return err;
 243
 244         si514_enable_output(data, false);
 245
 246         err = si514_set_muldiv(data, &settings);
 247         if (err < 0)
 248                 return err; /* Undefined state now, best to leave disabled */
 249
 250         /* Trigger calibration */
 251         err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
 252         if (err < 0)
 253                 return err;
 254
 255         /* Applying a new frequency can take up to 10ms */
 256         usleep_range(10000, 12000);
 257
 258         si514_enable_output(data, true);
 259
 260         return err;
 261 }
 262
 263 static const struct clk_ops si514_clk_ops = {
 264         .recalc_rate = si514_recalc_rate,
 265         .round_rate = si514_round_rate,
 266         .set_rate = si514_set_rate,
 267 };
 268
 269 static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
 270 {
 271         switch (reg) {
 272         case SI514_REG_CONTROL:
 273         case SI514_REG_RESET:
 274                 return true;
 275         default:
 276                 return false;
 277         }
 278 }
 279
 280 static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
 281 {
 282         switch (reg) {
 283         case SI514_REG_LP:
 284         case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
 285         case SI514_REG_OE_STATE:
 286         case SI514_REG_RESET:
 287         case SI514_REG_CONTROL:
 288                 return true;
 289         default:
 290                 return false;
 291         }
 292 }
 293
 294 static const struct regmap_config si514_regmap_config = {
 295         .reg_bits = 8,
 296         .val_bits = 8,
 297         .cache_type = REGCACHE_RBTREE,
 298         .max_register = SI514_REG_CONTROL,
 299         .writeable_reg = si514_regmap_is_writeable,
 300         .volatile_reg = si514_regmap_is_volatile,
 301 };
 302
 303 static int si514_probe(struct i2c_client *client,
 304                 const struct i2c_device_id *id)
 305 {
 306         struct clk_si514 *data;
 307         struct clk_init_data init;
 308         struct clk *clk;
 309         int err;
 310
 311         data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 312         if (!data)
 313                 return -ENOMEM;
 314
 315         init.ops = &si514_clk_ops;
 316         init.flags = CLK_IS_ROOT;
 317         init.num_parents = 0;
 318         data->hw.init = &init;
 319         data->i2c_client = client;
 320
 321         if (of_property_read_string(client->dev.of_node, "clock-output-names",
 322                         &init.name))
 323                 init.name = client->dev.of_node->name;
 324
 325         data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
 326         if (IS_ERR(data->regmap)) {
 327                 dev_err(&client->dev, "failed to allocate register map\n");
 328                 return PTR_ERR(data->regmap);
 329         }
 330
 331         i2c_set_clientdata(client, data);
 332
 333         clk = devm_clk_register(&client->dev, &data->hw);
 334         if (IS_ERR(clk)) {
 335                 dev_err(&client->dev, "clock registration failed\n");
 336                 return PTR_ERR(clk);
 337         }
 338         err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
 339                         clk);
 340         if (err) {
 341                 dev_err(&client->dev, "unable to add clk provider\n");
 342                 return err;
 343         }
 344
 345         return 0;
 346 }
 347
 348 static int si514_remove(struct i2c_client *client)
 349 {
 350         of_clk_del_provider(client->dev.of_node);
 351         return 0;
 352 }
 353
 354 static const struct i2c_device_id si514_id[] = {
 355         { "si514", 0 },
 356         { }
 357 };
 358 MODULE_DEVICE_TABLE(i2c, si514_id);
 359
 360 static const struct of_device_id clk_si514_of_match[] = {
 361         { .compatible = "silabs,si514" },
 362         { },
 363 };
 364 MODULE_DEVICE_TABLE(of, clk_si514_of_match);
 365
 366 static struct i2c_driver si514_driver = {
 367         .driver = {
 368                 .name = "si514",
 369                 .of_match_table = clk_si514_of_match,
 370         },
 371         .probe          = si514_probe,
 372         .remove         = si514_remove,
 373         .id_table       = si514_id,
 374 };
 375 module_i2c_driver(si514_driver);
 376
 377 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
 378 MODULE_DESCRIPTION("Si514 driver");
 379 MODULE_LICENSE("GPL");