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 = ceiling(parent->rate / divisor)
  28  * parent - fixed parent.  No clk_set_parent support
  29  */
  30
  31 #define div_mask(width) ((1 << (width)) - 1)
  32
  33 static unsigned int _get_table_maxdiv(const struct clk_div_table *table,
  34                                       u8 width)
  35 {
  36         unsigned int maxdiv = 0, mask = div_mask(width);
  37         const struct clk_div_table *clkt;
  38
  39         for (clkt = table; clkt->div; clkt++)
  40                 if (clkt->div > maxdiv && clkt->val <= mask)
  41                         maxdiv = clkt->div;
  42         return maxdiv;
  43 }
  44
  45 static unsigned int _get_table_mindiv(const struct clk_div_table *table)
  46 {
  47         unsigned int mindiv = UINT_MAX;
  48         const struct clk_div_table *clkt;
  49
  50         for (clkt = table; clkt->div; clkt++)
  51                 if (clkt->div < mindiv)
  52                         mindiv = clkt->div;
  53         return mindiv;
  54 }
  55
  56 static unsigned int _get_maxdiv(const struct clk_div_table *table, u8 width,
  57                                 unsigned long flags)
  58 {
  59         if (flags & CLK_DIVIDER_ONE_BASED)
  60                 return div_mask(width);
  61         if (flags & CLK_DIVIDER_POWER_OF_TWO)
  62                 return 1 << div_mask(width);
  63         if (table)
  64                 return _get_table_maxdiv(table, width);
  65         return div_mask(width) + 1;
  66 }
  67
  68 static unsigned int _get_table_div(const struct clk_div_table *table,
  69                                                         unsigned int val)
  70 {
  71         const struct clk_div_table *clkt;
  72
  73         for (clkt = table; clkt->div; clkt++)
  74                 if (clkt->val == val)
  75                         return clkt->div;
  76         return 0;
  77 }
  78
  79 static unsigned int _get_div(const struct clk_div_table *table,
  80                              unsigned int val, unsigned long flags, u8 width)
  81 {
  82         if (flags & CLK_DIVIDER_ONE_BASED)
  83                 return val;
  84         if (flags & CLK_DIVIDER_POWER_OF_TWO)
  85                 return 1 << val;
  86         if (flags & CLK_DIVIDER_MAX_AT_ZERO)
  87                 return val ? val : div_mask(width) + 1;
  88         if (table)
  89                 return _get_table_div(table, val);
  90         return val + 1;
  91 }
  92
  93 static unsigned int _get_table_val(const struct clk_div_table *table,
  94                                                         unsigned int div)
  95 {
  96         const struct clk_div_table *clkt;
  97
  98         for (clkt = table; clkt->div; clkt++)
  99                 if (clkt->div == div)
 100                         return clkt->val;
 101         return 0;
 102 }
 103
 104 static unsigned int _get_val(const struct clk_div_table *table,
 105                              unsigned int div, unsigned long flags, u8 width)
 106 {
 107         if (flags & CLK_DIVIDER_ONE_BASED)
 108                 return div;
 109         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 110                 return __ffs(div);
 111         if (flags & CLK_DIVIDER_MAX_AT_ZERO)
 112                 return (div == div_mask(width) + 1) ? 0 : div;
 113         if (table)
 114                 return  _get_table_val(table, div);
 115         return div - 1;
 116 }
 117
 118 unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
 119                                   unsigned int val,
 120                                   const struct clk_div_table *table,
 121                                   unsigned long flags)
 122 {
 123         struct clk_divider *divider = to_clk_divider(hw);
 124         unsigned int div;
 125
 126         div = _get_div(table, val, flags, divider->width);
 127         if (!div) {
 128                 WARN(!(flags & CLK_DIVIDER_ALLOW_ZERO),
 129                         "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
 130                         clk_hw_get_name(hw));
 131                 return parent_rate;
 132         }
 133
 134         return DIV_ROUND_UP_ULL((u64)parent_rate, div);
 135 }
 136 EXPORT_SYMBOL_GPL(divider_recalc_rate);
 137
 138 static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
 139                 unsigned long parent_rate)
 140 {
 141         struct clk_divider *divider = to_clk_divider(hw);
 142         unsigned int val;
 143
 144         val = clk_readl(divider->reg) >> divider->shift;
 145         val &= div_mask(divider->width);
 146
 147         return divider_recalc_rate(hw, parent_rate, val, divider->table,
 148                                    divider->flags);
 149 }
 150
 151 static bool _is_valid_table_div(const struct clk_div_table *table,
 152                                                          unsigned int div)
 153 {
 154         const struct clk_div_table *clkt;
 155
 156         for (clkt = table; clkt->div; clkt++)
 157                 if (clkt->div == div)
 158                         return true;
 159         return false;
 160 }
 161
 162 static bool _is_valid_div(const struct clk_div_table *table, unsigned int div,
 163                           unsigned long flags)
 164 {
 165         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 166                 return is_power_of_2(div);
 167         if (table)
 168                 return _is_valid_table_div(table, div);
 169         return true;
 170 }
 171
 172 static int _round_up_table(const struct clk_div_table *table, int div)
 173 {
 174         const struct clk_div_table *clkt;
 175         int up = INT_MAX;
 176
 177         for (clkt = table; clkt->div; clkt++) {
 178                 if (clkt->div == div)
 179                         return clkt->div;
 180                 else if (clkt->div < div)
 181                         continue;
 182
 183                 if ((clkt->div - div) < (up - div))
 184                         up = clkt->div;
 185         }
 186
 187         return up;
 188 }
 189
 190 static int _round_down_table(const struct clk_div_table *table, int div)
 191 {
 192         const struct clk_div_table *clkt;
 193         int down = _get_table_mindiv(table);
 194
 195         for (clkt = table; clkt->div; clkt++) {
 196                 if (clkt->div == div)
 197                         return clkt->div;
 198                 else if (clkt->div > div)
 199                         continue;
 200
 201                 if ((div - clkt->div) < (div - down))
 202                         down = clkt->div;
 203         }
 204
 205         return down;
 206 }
 207
 208 static int _div_round_up(const struct clk_div_table *table,
 209                          unsigned long parent_rate, unsigned long rate,
 210                          unsigned long flags)
 211 {
 212         int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
 213
 214         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 215                 div = __roundup_pow_of_two(div);
 216         if (table)
 217                 div = _round_up_table(table, div);
 218
 219         return div;
 220 }
 221
 222 static int _div_round_closest(const struct clk_div_table *table,
 223                               unsigned long parent_rate, unsigned long rate,
 224                               unsigned long flags)
 225 {
 226         int up, down;
 227         unsigned long up_rate, down_rate;
 228
 229         up = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
 230         down = parent_rate / rate;
 231
 232         if (flags & CLK_DIVIDER_POWER_OF_TWO) {
 233                 up = __roundup_pow_of_two(up);
 234                 down = __rounddown_pow_of_two(down);
 235         } else if (table) {
 236                 up = _round_up_table(table, up);
 237                 down = _round_down_table(table, down);
 238         }
 239
 240         up_rate = DIV_ROUND_UP_ULL((u64)parent_rate, up);
 241         down_rate = DIV_ROUND_UP_ULL((u64)parent_rate, down);
 242
 243         return (rate - up_rate) <= (down_rate - rate) ? up : down;
 244 }
 245
 246 static int _div_round(const struct clk_div_table *table,
 247                       unsigned long parent_rate, unsigned long rate,
 248                       unsigned long flags)
 249 {
 250         if (flags & CLK_DIVIDER_ROUND_CLOSEST)
 251                 return _div_round_closest(table, parent_rate, rate, flags);
 252
 253         return _div_round_up(table, parent_rate, rate, flags);
 254 }
 255
 256 static bool _is_best_div(unsigned long rate, unsigned long now,
 257                          unsigned long best, unsigned long flags)
 258 {
 259         if (flags & CLK_DIVIDER_ROUND_CLOSEST)
 260                 return abs(rate - now) < abs(rate - best);
 261
 262         return now <= rate && now > best;
 263 }
 264
 265 static int _next_div(const struct clk_div_table *table, int div,
 266                      unsigned long flags)
 267 {
 268         div++;
 269
 270         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 271                 return __roundup_pow_of_two(div);
 272         if (table)
 273                 return _round_up_table(table, div);
 274
 275         return div;
 276 }
 277
 278 static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 279                                unsigned long *best_parent_rate,
 280                                const struct clk_div_table *table, u8 width,
 281                                unsigned long flags)
 282 {
 283         int i, bestdiv = 0;
 284         unsigned long parent_rate, best = 0, now, maxdiv;
 285         unsigned long parent_rate_saved = *best_parent_rate;
 286
 287         if (!rate)
 288                 rate = 1;
 289
 290         maxdiv = _get_maxdiv(table, width, flags);
 291
 292         if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
 293                 parent_rate = *best_parent_rate;
 294                 bestdiv = _div_round(table, parent_rate, rate, flags);
 295                 bestdiv = bestdiv == 0 ? 1 : bestdiv;
 296                 bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
 297                 return bestdiv;
 298         }
 299
 300         /*
 301          * The maximum divider we can use without overflowing
 302          * unsigned long in rate * i below
 303          */
 304         maxdiv = min(ULONG_MAX / rate, maxdiv);
 305
 306         for (i = _next_div(table, 0, flags); i <= maxdiv;
 307                                              i = _next_div(table, i, flags)) {
 308                 if (rate * i == parent_rate_saved) {
 309                         /*
 310                          * It's the most ideal case if the requested rate can be
 311                          * divided from parent clock without needing to change
 312                          * parent rate, so return the divider immediately.
 313                          */
 314                         *best_parent_rate = parent_rate_saved;
 315                         return i;
 316                 }
 317                 parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw),
 318                                                rate * i);
 319                 now = DIV_ROUND_UP_ULL((u64)parent_rate, i);
 320                 if (_is_best_div(rate, now, best, flags)) {
 321                         bestdiv = i;
 322                         best = now;
 323                         *best_parent_rate = parent_rate;
 324                 }
 325         }
 326
 327         if (!bestdiv) {
 328                 bestdiv = _get_maxdiv(table, width, flags);
 329                 *best_parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw), 1);
 330         }
 331
 332         return bestdiv;
 333 }
 334
 335 long divider_round_rate(struct clk_hw *hw, unsigned long rate,
 336                         unsigned long *prate, const struct clk_div_table *table,
 337                         u8 width, unsigned long flags)
 338 {
 339         int div;
 340
 341         div = clk_divider_bestdiv(hw, rate, prate, table, width, flags);
 342
 343         return DIV_ROUND_UP_ULL((u64)*prate, div);
 344 }
 345 EXPORT_SYMBOL_GPL(divider_round_rate);
 346
 347 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 348                                 unsigned long *prate)
 349 {
 350         struct clk_divider *divider = to_clk_divider(hw);
 351         int bestdiv;
 352
 353         /* if read only, just return current value */
 354         if (divider->flags & CLK_DIVIDER_READ_ONLY) {
 355                 bestdiv = readl(divider->reg) >> divider->shift;
 356                 bestdiv &= div_mask(divider->width);
 357                 bestdiv = _get_div(divider->table, bestdiv, divider->flags,
 358                         divider->width);
 359                 return DIV_ROUND_UP_ULL((u64)*prate, bestdiv);
 360         }
 361
 362         return divider_round_rate(hw, rate, prate, divider->table,
 363                                   divider->width, divider->flags);
 364 }
 365
 366 int divider_get_val(unsigned long rate, unsigned long parent_rate,
 367                     const struct clk_div_table *table, u8 width,
 368                     unsigned long flags)
 369 {
 370         unsigned int div, value;
 371
 372         div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
 373
 374         if (!_is_valid_div(table, div, flags))
 375                 return -EINVAL;
 376
 377         value = _get_val(table, div, flags, width);
 378
 379         return min_t(unsigned int, value, div_mask(width));
 380 }
 381 EXPORT_SYMBOL_GPL(divider_get_val);
 382
 383 static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 384                                 unsigned long parent_rate)
 385 {
 386         struct clk_divider *divider = to_clk_divider(hw);
 387         unsigned int value;
 388         unsigned long flags = 0;
 389         u32 val;
 390
 391         value = divider_get_val(rate, parent_rate, divider->table,
 392                                 divider->width, divider->flags);
 393
 394         if (divider->lock)
 395                 spin_lock_irqsave(divider->lock, flags);
 396         else
 397                 __acquire(divider->lock);
 398
 399         if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
 400                 val = div_mask(divider->width) << (divider->shift + 16);
 401         } else {
 402                 val = clk_readl(divider->reg);
 403                 val &= ~(div_mask(divider->width) << divider->shift);
 404         }
 405         val |= value << divider->shift;
 406         clk_writel(val, divider->reg);
 407
 408         if (divider->lock)
 409                 spin_unlock_irqrestore(divider->lock, flags);
 410         else
 411                 __release(divider->lock);
 412
 413         return 0;
 414 }
 415
 416 const struct clk_ops clk_divider_ops = {
 417         .recalc_rate = clk_divider_recalc_rate,
 418         .round_rate = clk_divider_round_rate,
 419         .set_rate = clk_divider_set_rate,
 420 };
 421 EXPORT_SYMBOL_GPL(clk_divider_ops);
 422
 423 const struct clk_ops clk_divider_ro_ops = {
 424         .recalc_rate = clk_divider_recalc_rate,
 425         .round_rate = clk_divider_round_rate,
 426 };
 427 EXPORT_SYMBOL_GPL(clk_divider_ro_ops);
 428
 429 static struct clk *_register_divider(struct device *dev, const char *name,
 430                 const char *parent_name, unsigned long flags,
 431                 void __iomem *reg, u8 shift, u8 width,
 432                 u8 clk_divider_flags, const struct clk_div_table *table,
 433                 spinlock_t *lock)
 434 {
 435         struct clk_divider *div;
 436         struct clk *clk;
 437         struct clk_init_data init;
 438
 439         if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
 440                 if (width + shift > 16) {
 441                         pr_warn("divider value exceeds LOWORD field\n");
 442                         return ERR_PTR(-EINVAL);
 443                 }
 444         }
 445
 446         /* allocate the divider */
 447         div = kzalloc(sizeof(*div), GFP_KERNEL);
 448         if (!div)
 449                 return ERR_PTR(-ENOMEM);
 450
 451         init.name = name;
 452         if (clk_divider_flags & CLK_DIVIDER_READ_ONLY)
 453                 init.ops = &clk_divider_ro_ops;
 454         else
 455                 init.ops = &clk_divider_ops;
 456         init.flags = flags | CLK_IS_BASIC;
 457         init.parent_names = (parent_name ? &parent_name: NULL);
 458         init.num_parents = (parent_name ? 1 : 0);
 459
 460         /* struct clk_divider assignments */
 461         div->reg = reg;
 462         div->shift = shift;
 463         div->width = width;
 464         div->flags = clk_divider_flags;
 465         div->lock = lock;
 466         div->hw.init = &init;
 467         div->table = table;
 468
 469         /* register the clock */
 470         clk = clk_register(dev, &div->hw);
 471
 472         if (IS_ERR(clk))
 473                 kfree(div);
 474
 475         return clk;
 476 }
 477
 478 /**
 479  * clk_register_divider - register a divider clock with the clock framework
 480  * @dev: device registering this clock
 481  * @name: name of this clock
 482  * @parent_name: name of clock's parent
 483  * @flags: framework-specific flags
 484  * @reg: register address to adjust divider
 485  * @shift: number of bits to shift the bitfield
 486  * @width: width of the bitfield
 487  * @clk_divider_flags: divider-specific flags for this clock
 488  * @lock: shared register lock for this clock
 489  */
 490 struct clk *clk_register_divider(struct device *dev, const char *name,
 491                 const char *parent_name, unsigned long flags,
 492                 void __iomem *reg, u8 shift, u8 width,
 493                 u8 clk_divider_flags, spinlock_t *lock)
 494 {
 495         return _register_divider(dev, name, parent_name, flags, reg, shift,
 496                         width, clk_divider_flags, NULL, lock);
 497 }
 498 EXPORT_SYMBOL_GPL(clk_register_divider);
 499
 500 /**
 501  * clk_register_divider_table - register a table based divider clock with
 502  * the clock framework
 503  * @dev: device registering this clock
 504  * @name: name of this clock
 505  * @parent_name: name of clock's parent
 506  * @flags: framework-specific flags
 507  * @reg: register address to adjust divider
 508  * @shift: number of bits to shift the bitfield
 509  * @width: width of the bitfield
 510  * @clk_divider_flags: divider-specific flags for this clock
 511  * @table: array of divider/value pairs ending with a div set to 0
 512  * @lock: shared register lock for this clock
 513  */
 514 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 515                 const char *parent_name, unsigned long flags,
 516                 void __iomem *reg, u8 shift, u8 width,
 517                 u8 clk_divider_flags, const struct clk_div_table *table,
 518                 spinlock_t *lock)
 519 {
 520         return _register_divider(dev, name, parent_name, flags, reg, shift,
 521                         width, clk_divider_flags, table, lock);
 522 }
 523 EXPORT_SYMBOL_GPL(clk_register_divider_table);
 524
 525 void clk_unregister_divider(struct clk *clk)
 526 {
 527         struct clk_divider *div;
 528         struct clk_hw *hw;
 529
 530         hw = __clk_get_hw(clk);
 531         if (!hw)
 532                 return;
 533
 534         div = to_clk_divider(hw);
 535
 536         clk_unregister(clk);
 537         kfree(div);
 538 }
 539 EXPORT_SYMBOL_GPL(clk_unregister_divider);