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 = 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_maxdiv(struct clk_divider *divider)
  47 {
  48         if (divider->flags & CLK_DIVIDER_ONE_BASED)
  49                 return div_mask(divider);
  50         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
  51                 return 1 << div_mask(divider);
  52         if (divider->table)
  53                 return _get_table_maxdiv(divider->table);
  54         return div_mask(divider) + 1;
  55 }
  56
  57 static unsigned int _get_table_div(const struct clk_div_table *table,
  58                                                         unsigned int val)
  59 {
  60         const struct clk_div_table *clkt;
  61
  62         for (clkt = table; clkt->div; clkt++)
  63                 if (clkt->val == val)
  64                         return clkt->div;
  65         return 0;
  66 }
  67
  68 static unsigned int _get_div(struct clk_divider *divider, unsigned int val)
  69 {
  70         if (divider->flags & CLK_DIVIDER_ONE_BASED)
  71                 return val;
  72         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
  73                 return 1 << val;
  74         if (divider->table)
  75                 return _get_table_div(divider->table, val);
  76         return val + 1;
  77 }
  78
  79 static unsigned int _get_table_val(const struct clk_div_table *table,
  80                                                         unsigned int div)
  81 {
  82         const struct clk_div_table *clkt;
  83
  84         for (clkt = table; clkt->div; clkt++)
  85                 if (clkt->div == div)
  86                         return clkt->val;
  87         return 0;
  88 }
  89
  90 static unsigned int _get_val(struct clk_divider *divider, u8 div)
  91 {
  92         if (divider->flags & CLK_DIVIDER_ONE_BASED)
  93                 return div;
  94         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
  95                 return __ffs(div);
  96         if (divider->table)
  97                 return  _get_table_val(divider->table, div);
  98         return div - 1;
  99 }
 100
 101 static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
 102                 unsigned long parent_rate)
 103 {
 104         struct clk_divider *divider = to_clk_divider(hw);
 105         unsigned int div, val;
 106
 107         val = readl(divider->reg) >> divider->shift;
 108         val &= div_mask(divider);
 109
 110         div = _get_div(divider, val);
 111         if (!div) {
 112                 WARN(!(divider->flags & CLK_DIVIDER_ALLOW_ZERO),
 113                         "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
 114                         __clk_get_name(hw->clk));
 115                 return parent_rate;
 116         }
 117
 118         return parent_rate / div;
 119 }
 120
 121 /*
 122  * The reverse of DIV_ROUND_UP: The maximum number which
 123  * divided by m is r
 124  */
 125 #define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
 126
 127 static bool _is_valid_table_div(const struct clk_div_table *table,
 128                                                          unsigned int div)
 129 {
 130         const struct clk_div_table *clkt;
 131
 132         for (clkt = table; clkt->div; clkt++)
 133                 if (clkt->div == div)
 134                         return true;
 135         return false;
 136 }
 137
 138 static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
 139 {
 140         if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
 141                 return is_power_of_2(div);
 142         if (divider->table)
 143                 return _is_valid_table_div(divider->table, div);
 144         return true;
 145 }
 146
 147 static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 148                 unsigned long *best_parent_rate)
 149 {
 150         struct clk_divider *divider = to_clk_divider(hw);
 151         int i, bestdiv = 0;
 152         unsigned long parent_rate, best = 0, now, maxdiv;
 153         unsigned long parent_rate_saved = *best_parent_rate;
 154
 155         if (!rate)
 156                 rate = 1;
 157
 158         maxdiv = _get_maxdiv(divider);
 159
 160         if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
 161                 parent_rate = *best_parent_rate;
 162                 bestdiv = DIV_ROUND_UP(parent_rate, rate);
 163                 bestdiv = bestdiv == 0 ? 1 : bestdiv;
 164                 bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
 165                 return bestdiv;
 166         }
 167
 168         /*
 169          * The maximum divider we can use without overflowing
 170          * unsigned long in rate * i below
 171          */
 172         maxdiv = min(ULONG_MAX / rate, maxdiv);
 173
 174         for (i = 1; i <= maxdiv; i++) {
 175                 if (!_is_valid_div(divider, i))
 176                         continue;
 177                 if (rate * i == parent_rate_saved) {
 178                         /*
 179                          * It's the most ideal case if the requested rate can be
 180                          * divided from parent clock without needing to change
 181                          * parent rate, so return the divider immediately.
 182                          */
 183                         *best_parent_rate = parent_rate_saved;
 184                         return i;
 185                 }
 186                 parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
 187                                 MULT_ROUND_UP(rate, i));
 188                 now = parent_rate / i;
 189                 if (now <= rate && now > best) {
 190                         bestdiv = i;
 191                         best = now;
 192                         *best_parent_rate = parent_rate;
 193                 }
 194         }
 195
 196         if (!bestdiv) {
 197                 bestdiv = _get_maxdiv(divider);
 198                 *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
 199         }
 200
 201         return bestdiv;
 202 }
 203
 204 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 205                                 unsigned long *prate)
 206 {
 207         int div;
 208         div = clk_divider_bestdiv(hw, rate, prate);
 209
 210         return *prate / div;
 211 }
 212
 213 static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 214                                 unsigned long parent_rate)
 215 {
 216         struct clk_divider *divider = to_clk_divider(hw);
 217         unsigned int div, value;
 218         unsigned long flags = 0;
 219         u32 val;
 220
 221         div = parent_rate / rate;
 222         value = _get_val(divider, div);
 223
 224         if (value > div_mask(divider))
 225                 value = div_mask(divider);
 226
 227         if (divider->lock)
 228                 spin_lock_irqsave(divider->lock, flags);
 229
 230         if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
 231                 val = div_mask(divider) << (divider->shift + 16);
 232         } else {
 233                 val = readl(divider->reg);
 234                 val &= ~(div_mask(divider) << divider->shift);
 235         }
 236         val |= value << divider->shift;
 237         writel(val, divider->reg);
 238
 239         if (divider->lock)
 240                 spin_unlock_irqrestore(divider->lock, flags);
 241
 242         return 0;
 243 }
 244
 245 const struct clk_ops clk_divider_ops = {
 246         .recalc_rate = clk_divider_recalc_rate,
 247         .round_rate = clk_divider_round_rate,
 248         .set_rate = clk_divider_set_rate,
 249 };
 250 EXPORT_SYMBOL_GPL(clk_divider_ops);
 251
 252 static struct clk *_register_divider(struct device *dev, const char *name,
 253                 const char *parent_name, unsigned long flags,
 254                 void __iomem *reg, u8 shift, u8 width,
 255                 u8 clk_divider_flags, const struct clk_div_table *table,
 256                 spinlock_t *lock)
 257 {
 258         struct clk_divider *div;
 259         struct clk *clk;
 260         struct clk_init_data init;
 261
 262         if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
 263                 if (width + shift > 16) {
 264                         pr_warn("divider value exceeds LOWORD field\n");
 265                         return ERR_PTR(-EINVAL);
 266                 }
 267         }
 268
 269         /* allocate the divider */
 270         div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
 271         if (!div) {
 272                 pr_err("%s: could not allocate divider clk\n", __func__);
 273                 return ERR_PTR(-ENOMEM);
 274         }
 275
 276         init.name = name;
 277         init.ops = &clk_divider_ops;
 278         init.flags = flags | CLK_IS_BASIC;
 279         init.parent_names = (parent_name ? &parent_name: NULL);
 280         init.num_parents = (parent_name ? 1 : 0);
 281
 282         /* struct clk_divider assignments */
 283         div->reg = reg;
 284         div->shift = shift;
 285         div->width = width;
 286         div->flags = clk_divider_flags;
 287         div->lock = lock;
 288         div->hw.init = &init;
 289         div->table = table;
 290
 291         /* register the clock */
 292         clk = clk_register(dev, &div->hw);
 293
 294         if (IS_ERR(clk))
 295                 kfree(div);
 296
 297         return clk;
 298 }
 299
 300 /**
 301  * clk_register_divider - register a divider clock with the clock framework
 302  * @dev: device registering this clock
 303  * @name: name of this clock
 304  * @parent_name: name of clock's parent
 305  * @flags: framework-specific flags
 306  * @reg: register address to adjust divider
 307  * @shift: number of bits to shift the bitfield
 308  * @width: width of the bitfield
 309  * @clk_divider_flags: divider-specific flags for this clock
 310  * @lock: shared register lock for this clock
 311  */
 312 struct clk *clk_register_divider(struct device *dev, const char *name,
 313                 const char *parent_name, unsigned long flags,
 314                 void __iomem *reg, u8 shift, u8 width,
 315                 u8 clk_divider_flags, spinlock_t *lock)
 316 {
 317         return _register_divider(dev, name, parent_name, flags, reg, shift,
 318                         width, clk_divider_flags, NULL, lock);
 319 }
 320
 321 /**
 322  * clk_register_divider_table - register a table based divider clock with
 323  * the clock framework
 324  * @dev: device registering this clock
 325  * @name: name of this clock
 326  * @parent_name: name of clock's parent
 327  * @flags: framework-specific flags
 328  * @reg: register address to adjust divider
 329  * @shift: number of bits to shift the bitfield
 330  * @width: width of the bitfield
 331  * @clk_divider_flags: divider-specific flags for this clock
 332  * @table: array of divider/value pairs ending with a div set to 0
 333  * @lock: shared register lock for this clock
 334  */
 335 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 336                 const char *parent_name, unsigned long flags,
 337                 void __iomem *reg, u8 shift, u8 width,
 338                 u8 clk_divider_flags, const struct clk_div_table *table,
 339                 spinlock_t *lock)
 340 {
 341         return _register_divider(dev, name, parent_name, flags, reg, shift,
 342                         width, clk_divider_flags, table, lock);
 343 }