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(d)     ((1 << ((d)->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(struct clk_divider *divider)
  58 {
  59         if (divider->flags & CLK_DIVIDER_ONE_BASED)
  60                 return div_mask(divider);
  61         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
  62                 return 1 << div_mask(divider);
  63         if (divider->table)
  64                 return _get_table_maxdiv(divider->table);
  65         return div_mask(divider) + 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(struct clk_divider *divider, unsigned int val)
  80 {
  81         if (divider->flags & CLK_DIVIDER_ONE_BASED)
  82                 return val;
  83         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
  84                 return 1 << val;
  85         if (divider->table)
  86                 return _get_table_div(divider->table, val);
  87         return val + 1;
  88 }
  89
  90 static unsigned int _get_table_val(const struct clk_div_table *table,
  91                                                         unsigned int div)
  92 {
  93         const struct clk_div_table *clkt;
  94
  95         for (clkt = table; clkt->div; clkt++)
  96                 if (clkt->div == div)
  97                         return clkt->val;
  98         return 0;
  99 }
 100
 101 static unsigned int _get_val(struct clk_divider *divider, unsigned int div)
 102 {
 103         if (divider->flags & CLK_DIVIDER_ONE_BASED)
 104                 return div;
 105         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
 106                 return __ffs(div);
 107         if (divider->table)
 108                 return  _get_table_val(divider->table, div);
 109         return div - 1;
 110 }
 111
 112 static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
 113                 unsigned long parent_rate)
 114 {
 115         struct clk_divider *divider = to_clk_divider(hw);
 116         unsigned int div, val;
 117
 118         val = clk_readl(divider->reg) >> divider->shift;
 119         val &= div_mask(divider);
 120
 121         div = _get_div(divider, val);
 122         if (!div) {
 123                 WARN(!(divider->flags & CLK_DIVIDER_ALLOW_ZERO),
 124                         "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
 125                         __clk_get_name(hw->clk));
 126                 return parent_rate;
 127         }
 128
 129         return DIV_ROUND_UP(parent_rate, div);
 130 }
 131
 132 /*
 133  * The reverse of DIV_ROUND_UP: The maximum number which
 134  * divided by m is r
 135  */
 136 #define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
 137
 138 static bool _is_valid_table_div(const struct clk_div_table *table,
 139                                                          unsigned int div)
 140 {
 141         const struct clk_div_table *clkt;
 142
 143         for (clkt = table; clkt->div; clkt++)
 144                 if (clkt->div == div)
 145                         return true;
 146         return false;
 147 }
 148
 149 static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
 150 {
 151         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
 152                 return is_power_of_2(div);
 153         if (divider->table)
 154                 return _is_valid_table_div(divider->table, div);
 155         return true;
 156 }
 157
 158 static int _round_up_table(const struct clk_div_table *table, int div)
 159 {
 160         const struct clk_div_table *clkt;
 161         int up = INT_MAX;
 162
 163         for (clkt = table; clkt->div; clkt++) {
 164                 if (clkt->div == div)
 165                         return clkt->div;
 166                 else if (clkt->div < div)
 167                         continue;
 168
 169                 if ((clkt->div - div) < (up - div))
 170                         up = clkt->div;
 171         }
 172
 173         return up;
 174 }
 175
 176 static int _round_down_table(const struct clk_div_table *table, int div)
 177 {
 178         const struct clk_div_table *clkt;
 179         int down = _get_table_mindiv(table);
 180
 181         for (clkt = table; clkt->div; clkt++) {
 182                 if (clkt->div == div)
 183                         return clkt->div;
 184                 else if (clkt->div > div)
 185                         continue;
 186
 187                 if ((div - clkt->div) < (div - down))
 188                         down = clkt->div;
 189         }
 190
 191         return down;
 192 }
 193
 194 static int _div_round_up(struct clk_divider *divider,
 195                 unsigned long parent_rate, unsigned long rate)
 196 {
 197         int div = DIV_ROUND_UP(parent_rate, rate);
 198
 199         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
 200                 div = __roundup_pow_of_two(div);
 201         if (divider->table)
 202                 div = _round_up_table(divider->table, div);
 203
 204         return div;
 205 }
 206
 207 static int _div_round_closest(struct clk_divider *divider,
 208                 unsigned long parent_rate, unsigned long rate)
 209 {
 210         int up, down, div;
 211
 212         up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate);
 213
 214         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO) {
 215                 up = __roundup_pow_of_two(div);
 216                 down = __rounddown_pow_of_two(div);
 217         } else if (divider->table) {
 218                 up = _round_up_table(divider->table, div);
 219                 down = _round_down_table(divider->table, div);
 220         }
 221
 222         return (up - div) <= (div - down) ? up : down;
 223 }
 224
 225 static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
 226                 unsigned long rate)
 227 {
 228         if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
 229                 return _div_round_closest(divider, parent_rate, rate);
 230
 231         return _div_round_up(divider, parent_rate, rate);
 232 }
 233
 234 static bool _is_best_div(struct clk_divider *divider,
 235                 unsigned long rate, unsigned long now, unsigned long best)
 236 {
 237         if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
 238                 return abs(rate - now) < abs(rate - best);
 239
 240         return now <= rate && now > best;
 241 }
 242
 243 static int _next_div(struct clk_divider *divider, int div)
 244 {
 245         div++;
 246
 247         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
 248                 return __roundup_pow_of_two(div);
 249         if (divider->table)
 250                 return _round_up_table(divider->table, div);
 251
 252         return div;
 253 }
 254
 255 static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 256                 unsigned long *best_parent_rate)
 257 {
 258         struct clk_divider *divider = to_clk_divider(hw);
 259         int i, bestdiv = 0;
 260         unsigned long parent_rate, best = 0, now, maxdiv;
 261         unsigned long parent_rate_saved = *best_parent_rate;
 262
 263         if (!rate)
 264                 rate = 1;
 265
 266         /* if read only, just return current value */
 267         if (divider->flags & CLK_DIVIDER_READ_ONLY) {
 268                 bestdiv = readl(divider->reg) >> divider->shift;
 269                 bestdiv &= div_mask(divider);
 270                 bestdiv = _get_div(divider, bestdiv);
 271                 return bestdiv;
 272         }
 273
 274         maxdiv = _get_maxdiv(divider);
 275
 276         if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
 277                 parent_rate = *best_parent_rate;
 278                 bestdiv = _div_round(divider, parent_rate, rate);
 279                 bestdiv = bestdiv == 0 ? 1 : bestdiv;
 280                 bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
 281                 return bestdiv;
 282         }
 283
 284         /*
 285          * The maximum divider we can use without overflowing
 286          * unsigned long in rate * i below
 287          */
 288         maxdiv = min(ULONG_MAX / rate, maxdiv);
 289
 290         for (i = 1; i <= maxdiv; i = _next_div(divider, i)) {
 291                 if (!_is_valid_div(divider, i))
 292                         continue;
 293                 if (rate * i == parent_rate_saved) {
 294                         /*
 295                          * It's the most ideal case if the requested rate can be
 296                          * divided from parent clock without needing to change
 297                          * parent rate, so return the divider immediately.
 298                          */
 299                         *best_parent_rate = parent_rate_saved;
 300                         return i;
 301                 }
 302                 parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
 303                                 MULT_ROUND_UP(rate, i));
 304                 now = DIV_ROUND_UP(parent_rate, i);
 305                 if (_is_best_div(divider, rate, now, best)) {
 306                         bestdiv = i;
 307                         best = now;
 308                         *best_parent_rate = parent_rate;
 309                 }
 310         }
 311
 312         if (!bestdiv) {
 313                 bestdiv = _get_maxdiv(divider);
 314                 *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
 315         }
 316
 317         return bestdiv;
 318 }
 319
 320 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 321                                 unsigned long *prate)
 322 {
 323         int div;
 324         div = clk_divider_bestdiv(hw, rate, prate);
 325
 326         return DIV_ROUND_UP(*prate, div);
 327 }
 328
 329 static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 330                                 unsigned long parent_rate)
 331 {
 332         struct clk_divider *divider = to_clk_divider(hw);
 333         unsigned int div, value;
 334         unsigned long flags = 0;
 335         u32 val;
 336
 337         div = DIV_ROUND_UP(parent_rate, rate);
 338
 339         if (!_is_valid_div(divider, div))
 340                 return -EINVAL;
 341
 342         value = _get_val(divider, div);
 343
 344         if (value > div_mask(divider))
 345                 value = div_mask(divider);
 346
 347         if (divider->lock)
 348                 spin_lock_irqsave(divider->lock, flags);
 349
 350         if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
 351                 val = div_mask(divider) << (divider->shift + 16);
 352         } else {
 353                 val = clk_readl(divider->reg);
 354                 val &= ~(div_mask(divider) << divider->shift);
 355         }
 356         val |= value << divider->shift;
 357         clk_writel(val, divider->reg);
 358
 359         if (divider->lock)
 360                 spin_unlock_irqrestore(divider->lock, flags);
 361
 362         return 0;
 363 }
 364
 365 const struct clk_ops clk_divider_ops = {
 366         .recalc_rate = clk_divider_recalc_rate,
 367         .round_rate = clk_divider_round_rate,
 368         .set_rate = clk_divider_set_rate,
 369 };
 370 EXPORT_SYMBOL_GPL(clk_divider_ops);
 371
 372 static struct clk *_register_divider(struct device *dev, const char *name,
 373                 const char *parent_name, unsigned long flags,
 374                 void __iomem *reg, u8 shift, u8 width,
 375                 u8 clk_divider_flags, const struct clk_div_table *table,
 376                 spinlock_t *lock)
 377 {
 378         struct clk_divider *div;
 379         struct clk *clk;
 380         struct clk_init_data init;
 381
 382         if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
 383                 if (width + shift > 16) {
 384                         pr_warn("divider value exceeds LOWORD field\n");
 385                         return ERR_PTR(-EINVAL);
 386                 }
 387         }
 388
 389         /* allocate the divider */
 390         div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
 391         if (!div) {
 392                 pr_err("%s: could not allocate divider clk\n", __func__);
 393                 return ERR_PTR(-ENOMEM);
 394         }
 395
 396         init.name = name;
 397         init.ops = &clk_divider_ops;
 398         init.flags = flags | CLK_IS_BASIC;
 399         init.parent_names = (parent_name ? &parent_name: NULL);
 400         init.num_parents = (parent_name ? 1 : 0);
 401
 402         /* struct clk_divider assignments */
 403         div->reg = reg;
 404         div->shift = shift;
 405         div->width = width;
 406         div->flags = clk_divider_flags;
 407         div->lock = lock;
 408         div->hw.init = &init;
 409         div->table = table;
 410
 411         /* register the clock */
 412         clk = clk_register(dev, &div->hw);
 413
 414         if (IS_ERR(clk))
 415                 kfree(div);
 416
 417         return clk;
 418 }
 419
 420 /**
 421  * clk_register_divider - register a divider clock with the clock framework
 422  * @dev: device registering this clock
 423  * @name: name of this clock
 424  * @parent_name: name of clock's parent
 425  * @flags: framework-specific flags
 426  * @reg: register address to adjust divider
 427  * @shift: number of bits to shift the bitfield
 428  * @width: width of the bitfield
 429  * @clk_divider_flags: divider-specific flags for this clock
 430  * @lock: shared register lock for this clock
 431  */
 432 struct clk *clk_register_divider(struct device *dev, const char *name,
 433                 const char *parent_name, unsigned long flags,
 434                 void __iomem *reg, u8 shift, u8 width,
 435                 u8 clk_divider_flags, spinlock_t *lock)
 436 {
 437         return _register_divider(dev, name, parent_name, flags, reg, shift,
 438                         width, clk_divider_flags, NULL, lock);
 439 }
 440 EXPORT_SYMBOL_GPL(clk_register_divider);
 441
 442 /**
 443  * clk_register_divider_table - register a table based divider clock with
 444  * the clock framework
 445  * @dev: device registering this clock
 446  * @name: name of this clock
 447  * @parent_name: name of clock's parent
 448  * @flags: framework-specific flags
 449  * @reg: register address to adjust divider
 450  * @shift: number of bits to shift the bitfield
 451  * @width: width of the bitfield
 452  * @clk_divider_flags: divider-specific flags for this clock
 453  * @table: array of divider/value pairs ending with a div set to 0
 454  * @lock: shared register lock for this clock
 455  */
 456 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 457                 const char *parent_name, unsigned long flags,
 458                 void __iomem *reg, u8 shift, u8 width,
 459                 u8 clk_divider_flags, const struct clk_div_table *table,
 460                 spinlock_t *lock)
 461 {
 462         return _register_divider(dev, name, parent_name, flags, reg, shift,
 463                         width, clk_divider_flags, table, lock);
 464 }
 465 EXPORT_SYMBOL_GPL(clk_register_divider_table);