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 static bool _is_valid_table_div(const struct clk_div_table *table,
 148                                                          unsigned int div)
 149 {
 150         const struct clk_div_table *clkt;
 151
 152         for (clkt = table; clkt->div; clkt++)
 153                 if (clkt->div == div)
 154                         return true;
 155         return false;
 156 }
 157
 158 static bool _is_valid_div(const struct clk_div_table *table, unsigned int div,
 159                           unsigned long flags)
 160 {
 161         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 162                 return is_power_of_2(div);
 163         if (table)
 164                 return _is_valid_table_div(table, div);
 165         return true;
 166 }
 167
 168 static int _round_up_table(const struct clk_div_table *table, int div)
 169 {
 170         const struct clk_div_table *clkt;
 171         int up = INT_MAX;
 172
 173         for (clkt = table; clkt->div; clkt++) {
 174                 if (clkt->div == div)
 175                         return clkt->div;
 176                 else if (clkt->div < div)
 177                         continue;
 178
 179                 if ((clkt->div - div) < (up - div))
 180                         up = clkt->div;
 181         }
 182
 183         return up;
 184 }
 185
 186 static int _round_down_table(const struct clk_div_table *table, int div)
 187 {
 188         const struct clk_div_table *clkt;
 189         int down = _get_table_mindiv(table);
 190
 191         for (clkt = table; clkt->div; clkt++) {
 192                 if (clkt->div == div)
 193                         return clkt->div;
 194                 else if (clkt->div > div)
 195                         continue;
 196
 197                 if ((div - clkt->div) < (div - down))
 198                         down = clkt->div;
 199         }
 200
 201         return down;
 202 }
 203
 204 static int _div_round_up(const struct clk_div_table *table,
 205                          unsigned long parent_rate, unsigned long rate,
 206                          unsigned long flags)
 207 {
 208         int div = DIV_ROUND_UP(parent_rate, rate);
 209
 210         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 211                 div = __roundup_pow_of_two(div);
 212         if (table)
 213                 div = _round_up_table(table, div);
 214
 215         return div;
 216 }
 217
 218 static int _div_round_closest(const struct clk_div_table *table,
 219                               unsigned long parent_rate, unsigned long rate,
 220                               unsigned long flags)
 221 {
 222         int up, down, div;
 223
 224         up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate);
 225
 226         if (flags & CLK_DIVIDER_POWER_OF_TWO) {
 227                 up = __roundup_pow_of_two(div);
 228                 down = __rounddown_pow_of_two(div);
 229         } else if (table) {
 230                 up = _round_up_table(table, div);
 231                 down = _round_down_table(table, div);
 232         }
 233
 234         return (up - div) <= (div - down) ? up : down;
 235 }
 236
 237 static int _div_round(const struct clk_div_table *table,
 238                       unsigned long parent_rate, unsigned long rate,
 239                       unsigned long flags)
 240 {
 241         if (flags & CLK_DIVIDER_ROUND_CLOSEST)
 242                 return _div_round_closest(table, parent_rate, rate, flags);
 243
 244         return _div_round_up(table, parent_rate, rate, flags);
 245 }
 246
 247 static bool _is_best_div(unsigned long rate, unsigned long now,
 248                          unsigned long best, unsigned long flags)
 249 {
 250         if (flags & CLK_DIVIDER_ROUND_CLOSEST)
 251                 return abs(rate - now) < abs(rate - best);
 252
 253         return now <= rate && now > best;
 254 }
 255
 256 static int _next_div(const struct clk_div_table *table, int div,
 257                      unsigned long flags)
 258 {
 259         div++;
 260
 261         if (flags & CLK_DIVIDER_POWER_OF_TWO)
 262                 return __roundup_pow_of_two(div);
 263         if (table)
 264                 return _round_up_table(table, div);
 265
 266         return div;
 267 }
 268
 269 static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 270                                unsigned long *best_parent_rate,
 271                                const struct clk_div_table *table, u8 width,
 272                                unsigned long flags)
 273 {
 274         int i, bestdiv = 0;
 275         unsigned long parent_rate, best = 0, now, maxdiv;
 276         unsigned long parent_rate_saved = *best_parent_rate;
 277
 278         if (!rate)
 279                 rate = 1;
 280
 281         maxdiv = _get_maxdiv(table, width, flags);
 282
 283         if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
 284                 parent_rate = *best_parent_rate;
 285                 bestdiv = _div_round(table, parent_rate, rate, flags);
 286                 bestdiv = bestdiv == 0 ? 1 : bestdiv;
 287                 bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
 288                 return bestdiv;
 289         }
 290
 291         /*
 292          * The maximum divider we can use without overflowing
 293          * unsigned long in rate * i below
 294          */
 295         maxdiv = min(ULONG_MAX / rate, maxdiv);
 296
 297         for (i = 1; i <= maxdiv; i = _next_div(table, i, flags)) {
 298                 if (!_is_valid_div(table, i, flags))
 299                         continue;
 300                 if (rate * i == parent_rate_saved) {
 301                         /*
 302                          * It's the most ideal case if the requested rate can be
 303                          * divided from parent clock without needing to change
 304                          * parent rate, so return the divider immediately.
 305                          */
 306                         *best_parent_rate = parent_rate_saved;
 307                         return i;
 308                 }
 309                 parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
 310                                                rate * i);
 311                 now = DIV_ROUND_UP(parent_rate, i);
 312                 if (_is_best_div(rate, now, best, flags)) {
 313                         bestdiv = i;
 314                         best = now;
 315                         *best_parent_rate = parent_rate;
 316                 }
 317         }
 318
 319         if (!bestdiv) {
 320                 bestdiv = _get_maxdiv(table, width, flags);
 321                 *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
 322         }
 323
 324         return bestdiv;
 325 }
 326
 327 long divider_round_rate(struct clk_hw *hw, unsigned long rate,
 328                         unsigned long *prate, const struct clk_div_table *table,
 329                         u8 width, unsigned long flags)
 330 {
 331         int div;
 332
 333         div = clk_divider_bestdiv(hw, rate, prate, table, width, flags);
 334
 335         return DIV_ROUND_UP(*prate, div);
 336 }
 337 EXPORT_SYMBOL_GPL(divider_round_rate);
 338
 339 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 340                                 unsigned long *prate)
 341 {
 342         struct clk_divider *divider = to_clk_divider(hw);
 343         int bestdiv;
 344
 345         /* if read only, just return current value */
 346         if (divider->flags & CLK_DIVIDER_READ_ONLY) {
 347                 bestdiv = readl(divider->reg) >> divider->shift;
 348                 bestdiv &= div_mask(divider->width);
 349                 bestdiv = _get_div(divider->table, bestdiv, divider->flags);
 350                 return DIV_ROUND_UP(*prate, bestdiv);
 351         }
 352
 353         return divider_round_rate(hw, rate, prate, divider->table,
 354                                   divider->width, divider->flags);
 355 }
 356
 357 int divider_get_val(unsigned long rate, unsigned long parent_rate,
 358                     const struct clk_div_table *table, u8 width,
 359                     unsigned long flags)
 360 {
 361         unsigned int div, value;
 362
 363         div = DIV_ROUND_UP(parent_rate, rate);
 364
 365         if (!_is_valid_div(table, div, flags))
 366                 return -EINVAL;
 367
 368         value = _get_val(table, div, flags);
 369
 370         return min_t(unsigned int, value, div_mask(width));
 371 }
 372 EXPORT_SYMBOL_GPL(divider_get_val);
 373
 374 static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 375                                 unsigned long parent_rate)
 376 {
 377         struct clk_divider *divider = to_clk_divider(hw);
 378         unsigned int value;
 379         unsigned long flags = 0;
 380         u32 val;
 381
 382         value = divider_get_val(rate, parent_rate, divider->table,
 383                                 divider->width, divider->flags);
 384
 385         if (divider->lock)
 386                 spin_lock_irqsave(divider->lock, flags);
 387
 388         if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
 389                 val = div_mask(divider->width) << (divider->shift + 16);
 390         } else {
 391                 val = clk_readl(divider->reg);
 392                 val &= ~(div_mask(divider->width) << divider->shift);
 393         }
 394         val |= value << divider->shift;
 395         clk_writel(val, divider->reg);
 396
 397         if (divider->lock)
 398                 spin_unlock_irqrestore(divider->lock, flags);
 399
 400         return 0;
 401 }
 402
 403 const struct clk_ops clk_divider_ops = {
 404         .recalc_rate = clk_divider_recalc_rate,
 405         .round_rate = clk_divider_round_rate,
 406         .set_rate = clk_divider_set_rate,
 407 };
 408 EXPORT_SYMBOL_GPL(clk_divider_ops);
 409
 410 static struct clk *_register_divider(struct device *dev, const char *name,
 411                 const char *parent_name, unsigned long flags,
 412                 void __iomem *reg, u8 shift, u8 width,
 413                 u8 clk_divider_flags, const struct clk_div_table *table,
 414                 spinlock_t *lock)
 415 {
 416         struct clk_divider *div;
 417         struct clk *clk;
 418         struct clk_init_data init;
 419
 420         if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
 421                 if (width + shift > 16) {
 422                         pr_warn("divider value exceeds LOWORD field\n");
 423                         return ERR_PTR(-EINVAL);
 424                 }
 425         }
 426
 427         /* allocate the divider */
 428         div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
 429         if (!div) {
 430                 pr_err("%s: could not allocate divider clk\n", __func__);
 431                 return ERR_PTR(-ENOMEM);
 432         }
 433
 434         init.name = name;
 435         init.ops = &clk_divider_ops;
 436         init.flags = flags | CLK_IS_BASIC;
 437         init.parent_names = (parent_name ? &parent_name: NULL);
 438         init.num_parents = (parent_name ? 1 : 0);
 439
 440         /* struct clk_divider assignments */
 441         div->reg = reg;
 442         div->shift = shift;
 443         div->width = width;
 444         div->flags = clk_divider_flags;
 445         div->lock = lock;
 446         div->hw.init = &init;
 447         div->table = table;
 448
 449         /* register the clock */
 450         clk = clk_register(dev, &div->hw);
 451
 452         if (IS_ERR(clk))
 453                 kfree(div);
 454
 455         return clk;
 456 }
 457
 458 /**
 459  * clk_register_divider - register a divider clock with the clock framework
 460  * @dev: device registering this clock
 461  * @name: name of this clock
 462  * @parent_name: name of clock's parent
 463  * @flags: framework-specific flags
 464  * @reg: register address to adjust divider
 465  * @shift: number of bits to shift the bitfield
 466  * @width: width of the bitfield
 467  * @clk_divider_flags: divider-specific flags for this clock
 468  * @lock: shared register lock for this clock
 469  */
 470 struct clk *clk_register_divider(struct device *dev, const char *name,
 471                 const char *parent_name, unsigned long flags,
 472                 void __iomem *reg, u8 shift, u8 width,
 473                 u8 clk_divider_flags, spinlock_t *lock)
 474 {
 475         return _register_divider(dev, name, parent_name, flags, reg, shift,
 476                         width, clk_divider_flags, NULL, lock);
 477 }
 478 EXPORT_SYMBOL_GPL(clk_register_divider);
 479
 480 /**
 481  * clk_register_divider_table - register a table based divider clock with
 482  * the clock framework
 483  * @dev: device registering this clock
 484  * @name: name of this clock
 485  * @parent_name: name of clock's parent
 486  * @flags: framework-specific flags
 487  * @reg: register address to adjust divider
 488  * @shift: number of bits to shift the bitfield
 489  * @width: width of the bitfield
 490  * @clk_divider_flags: divider-specific flags for this clock
 491  * @table: array of divider/value pairs ending with a div set to 0
 492  * @lock: shared register lock for this clock
 493  */
 494 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 495                 const char *parent_name, unsigned long flags,
 496                 void __iomem *reg, u8 shift, u8 width,
 497                 u8 clk_divider_flags, const struct clk_div_table *table,
 498                 spinlock_t *lock)
 499 {
 500         return _register_divider(dev, name, parent_name, flags, reg, shift,
 501                         width, clk_divider_flags, table, lock);
 502 }
 503 EXPORT_SYMBOL_GPL(clk_register_divider_table);
 504
 505 void clk_unregister_divider(struct clk *clk)
 506 {
 507         struct clk_divider *div;
 508         struct clk_hw *hw;
 509
 510         hw = __clk_get_hw(clk);
 511         if (!hw)
 512                 return;
 513
 514         div = to_clk_divider(hw);
 515
 516         clk_unregister(clk);
 517         kfree(div);
 518 }
 519 EXPORT_SYMBOL_GPL(clk_unregister_divider);