drivers/clk/clk-divider.c

   1 /*
   2  * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
   3  * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
   4  * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * Adjustable divider clock implementation
  11  */
  12
  13 #include <linux/clk-provider.h>
  14 #include <linux/module.h>
  15 #include <linux/slab.h>
  16 #include <linux/io.h>
  17 #include <linux/err.h>
  18 #include <linux/string.h>
  19 #include <linux/log2.h>
  20
  21 /*
  22  * DOC: basic adjustable divider clock that cannot gate
  23  *
  24  * Traits of this clock:
  25  * prepare - clk_prepare only ensures that parents are prepared
  26  * enable - clk_enable only ensures that parents are enabled
  27  * rate - rate is adjustable.  clk->rate = DIV_ROUND_UP(parent->rate / divisor)
  28  * parent - fixed parent.  No clk_set_parent support
  29  */
  30
  31 #define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)
  32
  33 #define div_mask(width) ((1 << (width)) - 1)
  34
  35 static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
  36 {
  37         unsigned int maxdiv = 0;
  38         const struct clk_div_table *clkt;
  39
  40         for (clkt = table; clkt->div; clkt++)
  41                 if (clkt->div > maxdiv)
  42                         maxdiv = clkt->div;
  43         return maxdiv;
  44 }
  45
  46 static unsigned int _get_table_mindiv(const struct clk_div_table *table)
  47 {
  48         unsigned int mindiv = UINT_MAX;
  49         const struct clk_div_table *clkt;
  50
  51         for (clkt = table; clkt->div; clkt++)
  52                 if (clkt->div < mindiv)
  53                         mindiv = clkt->div;
  54         return mindiv;
  55 }
  56
  57 static unsigned int _get_maxdiv(const struct clk_div_table *table, u8 width,
  58                                 unsigned long flags)
  59 {
  60         if (flags & CLK_DIVIDER_ONE_BASED)
  61                 return div_mask(width);
  62         if (flags & CLK_DIVIDER_POWER_OF_TWO)
  63                 return 1 << div_mask(width);
  64         if (table)
  65                 return _get_table_maxdiv(table);
  66         return div_mask(width) + 1;
  67 }
  68
  69 static unsigned int _get_table_div(const struct clk_div_table *table,
  70                                                         unsigned int val)
  71 {
  72         const struct clk_div_table *clkt;
  73
  74         for (clkt = table; clkt->div; clkt++)
  75                 if (clkt->val == val)
  76                         return clkt->div;
  77         return 0;
  78 }
  79
  80 static unsigned int _get_div(const struct clk_div_table *table,
  81                              unsigned int val, unsigned long flags)
  82 {
  83         if (flags & CLK_DIVIDER_ONE_BASED)
  84                 return val;
  85         if (flags & CLK_DIVIDER_POWER_OF_TWO)
  86                 return 1 << val;
  87         if (table)
  88                 return _get_table_div(table, val);
  89         return val + 1;
  90 }
  91
  92 static unsigned int _get_table_val(const struct clk_div_table *table,
  93                                                         unsigned int div)
  94 {
  95         const struct clk_div_table *clkt;
  96
  97         for (clkt = table; clkt->div; clkt++)
  98                 if (clkt->div == div)
  99                         return clkt->val;
 100         return 0;
 101 }
 102
 103 static unsigned int _get_val(const struct clk_div_table *table,
 104                              unsigned int div, unsigned long flags)
 105 {
 106         if (flags & CLK_DIVIDER_ONE_BASED)
 107                 return div;
 108         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 109                 return __ffs(div);
 110         if (table)
 111                 return  _get_table_val(table, div);
 112         return div - 1;
 113 }
 114
 115 unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
 116                                   unsigned int val,
 117                                   const struct clk_div_table *table,
 118                                   unsigned long flags)
 119 {
 120         unsigned int div;
 121
 122         div = _get_div(table, val, flags);
 123         if (!div) {
 124                 WARN(!(flags & CLK_DIVIDER_ALLOW_ZERO),
 125                         "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
 126                         __clk_get_name(hw->clk));
 127                 return parent_rate;
 128         }
 129
 130         return DIV_ROUND_UP(parent_rate, div);
 131 }
 132 EXPORT_SYMBOL_GPL(divider_recalc_rate);
 133
 134 static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
 135                 unsigned long parent_rate)
 136 {
 137         struct clk_divider *divider = to_clk_divider(hw);
 138         unsigned int val;
 139
 140         val = clk_readl(divider->reg) >> divider->shift;
 141         val &= div_mask(divider->width);
 142
 143         return divider_recalc_rate(hw, parent_rate, val, divider->table,
 144                                    divider->flags);
 145 }
 146
 147 /*
 148  * The reverse of DIV_ROUND_UP: The maximum number which
 149  * divided by m is r
 150  */
 151 #define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
 152
 153 static bool _is_valid_table_div(const struct clk_div_table *table,
 154                                                          unsigned int div)
 155 {
 156         const struct clk_div_table *clkt;
 157
 158         for (clkt = table; clkt->div; clkt++)
 159                 if (clkt->div == div)
 160                         return true;
 161         return false;
 162 }
 163
 164 static bool _is_valid_div(const struct clk_div_table *table, unsigned int div,
 165                           unsigned long flags)
 166 {
 167         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 168                 return is_power_of_2(div);
 169         if (table)
 170                 return _is_valid_table_div(table, div);
 171         return true;
 172 }
 173
 174 static int _round_up_table(const struct clk_div_table *table, int div)
 175 {
 176         const struct clk_div_table *clkt;
 177         int up = INT_MAX;
 178
 179         for (clkt = table; clkt->div; clkt++) {
 180                 if (clkt->div == div)
 181                         return clkt->div;
 182                 else if (clkt->div < div)
 183                         continue;
 184
 185                 if ((clkt->div - div) < (up - div))
 186                         up = clkt->div;
 187         }
 188
 189         return up;
 190 }
 191
 192 static int _round_down_table(const struct clk_div_table *table, int div)
 193 {
 194         const struct clk_div_table *clkt;
 195         int down = _get_table_mindiv(table);
 196
 197         for (clkt = table; clkt->div; clkt++) {
 198                 if (clkt->div == div)
 199                         return clkt->div;
 200                 else if (clkt->div > div)
 201                         continue;
 202
 203                 if ((div - clkt->div) < (div - down))
 204                         down = clkt->div;
 205         }
 206
 207         return down;
 208 }
 209
 210 static int _div_round_up(const struct clk_div_table *table,
 211                          unsigned long parent_rate, unsigned long rate,
 212                          unsigned long flags)
 213 {
 214         int div = DIV_ROUND_UP(parent_rate, rate);
 215
 216         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 217                 div = __roundup_pow_of_two(div);
 218         if (table)
 219                 div = _round_up_table(table, div);
 220
 221         return div;
 222 }
 223
 224 static int _div_round_closest(const struct clk_div_table *table,
 225                               unsigned long parent_rate, unsigned long rate,
 226                               unsigned long flags)
 227 {
 228         int up, down, div;
 229
 230         up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate);
 231
 232         if (flags & CLK_DIVIDER_POWER_OF_TWO) {
 233                 up = __roundup_pow_of_two(div);
 234                 down = __rounddown_pow_of_two(div);
 235         } else if (table) {
 236                 up = _round_up_table(table, div);
 237                 down = _round_down_table(table, div);
 238         }
 239
 240         return (up - div) <= (div - down) ? up : down;
 241 }
 242
 243 static int _div_round(const struct clk_div_table *table,
 244                       unsigned long parent_rate, unsigned long rate,
 245                       unsigned long flags)
 246 {
 247         if (flags & CLK_DIVIDER_ROUND_CLOSEST)
 248                 return _div_round_closest(table, parent_rate, rate, flags);
 249
 250         return _div_round_up(table, parent_rate, rate, flags);
 251 }
 252
 253 static bool _is_best_div(unsigned long rate, unsigned long now,
 254                          unsigned long best, unsigned long flags)
 255 {
 256         if (flags & CLK_DIVIDER_ROUND_CLOSEST)
 257                 return abs(rate - now) < abs(rate - best);
 258
 259         return now <= rate && now > best;
 260 }
 261
 262 static int _next_div(const struct clk_div_table *table, int div,
 263                      unsigned long flags)
 264 {
 265         div++;
 266
 267         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 268                 return __roundup_pow_of_two(div);
 269         if (table)
 270                 return _round_up_table(table, div);
 271
 272         return div;
 273 }
 274
 275 static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 276                                unsigned long *best_parent_rate,
 277                                const struct clk_div_table *table, u8 width,
 278                                unsigned long flags)
 279 {
 280         int i, bestdiv = 0;
 281         unsigned long parent_rate, best = 0, now, maxdiv;
 282         unsigned long parent_rate_saved = *best_parent_rate;
 283
 284         if (!rate)
 285                 rate = 1;
 286
 287         maxdiv = _get_maxdiv(table, width, flags);
 288
 289         if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
 290                 parent_rate = *best_parent_rate;
 291                 bestdiv = _div_round(table, parent_rate, rate, flags);
 292                 bestdiv = bestdiv == 0 ? 1 : bestdiv;
 293                 bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
 294                 return bestdiv;
 295         }
 296
 297         /*
 298          * The maximum divider we can use without overflowing
 299          * unsigned long in rate * i below
 300          */
 301         maxdiv = min(ULONG_MAX / rate, maxdiv);
 302
 303         for (i = 1; i <= maxdiv; i = _next_div(table, i, flags)) {
 304                 if (!_is_valid_div(table, i, flags))
 305                         continue;
 306                 if (rate * i == parent_rate_saved) {
 307                         /*
 308                          * It's the most ideal case if the requested rate can be
 309                          * divided from parent clock without needing to change
 310                          * parent rate, so return the divider immediately.
 311                          */
 312                         *best_parent_rate = parent_rate_saved;
 313                         return i;
 314                 }
 315                 parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
 316                                 MULT_ROUND_UP(rate, i));
 317                 now = DIV_ROUND_UP(parent_rate, i);
 318                 if (_is_best_div(rate, now, best, flags)) {
 319                         bestdiv = i;
 320                         best = now;
 321                         *best_parent_rate = parent_rate;
 322                 }
 323         }
 324
 325         if (!bestdiv) {
 326                 bestdiv = _get_maxdiv(table, width, flags);
 327                 *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
 328         }
 329
 330         return bestdiv;
 331 }
 332
 333 long divider_round_rate(struct clk_hw *hw, unsigned long rate,
 334                         unsigned long *prate, const struct clk_div_table *table,
 335                         u8 width, unsigned long flags)
 336 {
 337         int div;
 338
 339         div = clk_divider_bestdiv(hw, rate, prate, table, width, flags);
 340
 341         return DIV_ROUND_UP(*prate, div);
 342 }
 343 EXPORT_SYMBOL_GPL(divider_round_rate);
 344
 345 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 346                                 unsigned long *prate)
 347 {
 348         struct clk_divider *divider = to_clk_divider(hw);
 349         int bestdiv;
 350
 351         /* if read only, just return current value */
 352         if (divider->flags & CLK_DIVIDER_READ_ONLY) {
 353                 bestdiv = readl(divider->reg) >> divider->shift;
 354                 bestdiv &= div_mask(divider->width);
 355                 bestdiv = _get_div(divider->table, bestdiv, divider->flags);
 356                 return bestdiv;
 357         }
 358
 359         return divider_round_rate(hw, rate, prate, divider->table,
 360                                   divider->width, divider->flags);
 361 }
 362
 363 int divider_get_val(unsigned long rate, unsigned long parent_rate,
 364                     const struct clk_div_table *table, u8 width,
 365                     unsigned long flags)
 366 {
 367         unsigned int div, value;
 368
 369         div = DIV_ROUND_UP(parent_rate, rate);
 370
 371         if (!_is_valid_div(table, div, flags))
 372                 return -EINVAL;
 373
 374         value = _get_val(table, div, flags);
 375
 376         return min_t(unsigned int, value, div_mask(width));
 377 }
 378 EXPORT_SYMBOL_GPL(divider_get_val);
 379
 380 static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 381                                 unsigned long parent_rate)
 382 {
 383         struct clk_divider *divider = to_clk_divider(hw);
 384         unsigned int value;
 385         unsigned long flags = 0;
 386         u32 val;
 387
 388         value = divider_get_val(rate, parent_rate, divider->table,
 389                                 divider->width, divider->flags);
 390
 391         if (divider->lock)
 392                 spin_lock_irqsave(divider->lock, flags);
 393
 394         if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
 395                 val = div_mask(divider->width) << (divider->shift + 16);
 396         } else {
 397                 val = clk_readl(divider->reg);
 398                 val &= ~(div_mask(divider->width) << divider->shift);
 399         }
 400         val |= value << divider->shift;
 401         clk_writel(val, divider->reg);
 402
 403         if (divider->lock)
 404                 spin_unlock_irqrestore(divider->lock, flags);
 405
 406         return 0;
 407 }
 408
 409 const struct clk_ops clk_divider_ops = {
 410         .recalc_rate = clk_divider_recalc_rate,
 411         .round_rate = clk_divider_round_rate,
 412         .set_rate = clk_divider_set_rate,
 413 };
 414 EXPORT_SYMBOL_GPL(clk_divider_ops);
 415
 416 static struct clk *_register_divider(struct device *dev, const char *name,
 417                 const char *parent_name, unsigned long flags,
 418                 void __iomem *reg, u8 shift, u8 width,
 419                 u8 clk_divider_flags, const struct clk_div_table *table,
 420                 spinlock_t *lock)
 421 {
 422         struct clk_divider *div;
 423         struct clk *clk;
 424         struct clk_init_data init;
 425
 426         if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
 427                 if (width + shift > 16) {
 428                         pr_warn("divider value exceeds LOWORD field\n");
 429                         return ERR_PTR(-EINVAL);
 430                 }
 431         }
 432
 433         /* allocate the divider */
 434         div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
 435         if (!div) {
 436                 pr_err("%s: could not allocate divider clk\n", __func__);
 437                 return ERR_PTR(-ENOMEM);
 438         }
 439
 440         init.name = name;
 441         init.ops = &clk_divider_ops;
 442         init.flags = flags | CLK_IS_BASIC;
 443         init.parent_names = (parent_name ? &parent_name: NULL);
 444         init.num_parents = (parent_name ? 1 : 0);
 445
 446         /* struct clk_divider assignments */
 447         div->reg = reg;
 448         div->shift = shift;
 449         div->width = width;
 450         div->flags = clk_divider_flags;
 451         div->lock = lock;
 452         div->hw.init = &init;
 453         div->table = table;
 454
 455         /* register the clock */
 456         clk = clk_register(dev, &div->hw);
 457
 458         if (IS_ERR(clk))
 459                 kfree(div);
 460
 461         return clk;
 462 }
 463
 464 /**
 465  * clk_register_divider - register a divider clock with the clock framework
 466  * @dev: device registering this clock
 467  * @name: name of this clock
 468  * @parent_name: name of clock's parent
 469  * @flags: framework-specific flags
 470  * @reg: register address to adjust divider
 471  * @shift: number of bits to shift the bitfield
 472  * @width: width of the bitfield
 473  * @clk_divider_flags: divider-specific flags for this clock
 474  * @lock: shared register lock for this clock
 475  */
 476 struct clk *clk_register_divider(struct device *dev, const char *name,
 477                 const char *parent_name, unsigned long flags,
 478                 void __iomem *reg, u8 shift, u8 width,
 479                 u8 clk_divider_flags, spinlock_t *lock)
 480 {
 481         return _register_divider(dev, name, parent_name, flags, reg, shift,
 482                         width, clk_divider_flags, NULL, lock);
 483 }
 484 EXPORT_SYMBOL_GPL(clk_register_divider);
 485
 486 /**
 487  * clk_register_divider_table - register a table based divider clock with
 488  * the clock framework
 489  * @dev: device registering this clock
 490  * @name: name of this clock
 491  * @parent_name: name of clock's parent
 492  * @flags: framework-specific flags
 493  * @reg: register address to adjust divider
 494  * @shift: number of bits to shift the bitfield
 495  * @width: width of the bitfield
 496  * @clk_divider_flags: divider-specific flags for this clock
 497  * @table: array of divider/value pairs ending with a div set to 0
 498  * @lock: shared register lock for this clock
 499  */
 500 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 501                 const char *parent_name, unsigned long flags,
 502                 void __iomem *reg, u8 shift, u8 width,
 503                 u8 clk_divider_flags, const struct clk_div_table *table,
 504                 spinlock_t *lock)
 505 {
 506         return _register_divider(dev, name, parent_name, flags, reg, shift,
 507                         width, clk_divider_flags, table, lock);
 508 }
 509 EXPORT_SYMBOL_GPL(clk_register_divider_table);
 510
 511 void clk_unregister_divider(struct clk *clk)
 512 {
 513         struct clk_divider *div;
 514         struct clk_hw *hw;
 515
 516         hw = __clk_get_hw(clk);
 517         if (!hw)
 518                 return;
 519
 520         div = to_clk_divider(hw);
 521
 522         clk_unregister(clk);
 523         kfree(div);
 524 }
 525 EXPORT_SYMBOL_GPL(clk_unregister_divider);