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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (C) 2014 Intel Corporation4 *5 * Adjustable fractional divider clock implementation.6 * Uses rational best approximation algorithm.7 *8 * Output is calculated as9 *10 * rate = (m / n) * parent_rate (1)11 *12 * This is useful when we have a prescaler block which asks for13 * m (numerator) and n (denominator) values to be provided to satisfy14 * the (1) as much as possible.15 *16 * Since m and n have the limitation by a range, e.g.17 *18 * n >= 1, n < N_width, where N_width = 2^nwidth (2)19 *20 * for some cases the output may be saturated. Hence, from (1) and (2),21 * assuming the worst case when m = 1, the inequality22 *23 * floor(log2(parent_rate / rate)) <= nwidth (3)24 *25 * may be derived. Thus, in cases when26 *27 * (parent_rate / rate) >> N_width (4)28 *29 * we might scale up the rate by 2^scale (see the description of30 * CLK_FRAC_DIVIDER_POWER_OF_TWO_PS for additional information), where31 *32 * scale = floor(log2(parent_rate / rate)) - nwidth (5)33 *34 * and assume that the IP, that needs m and n, has also its own35 * prescaler, which is capable to divide by 2^scale. In this way36 * we get the denominator to satisfy the desired range (2) and37 * at the same time a much better result of m and n than simple38 * saturated values.39 */40 41#include <linux/debugfs.h>42#include <linux/device.h>43#include <linux/io.h>44#include <linux/math.h>45#include <linux/module.h>46#include <linux/rational.h>47#include <linux/slab.h>48 49#include <linux/clk-provider.h>50 51#include "clk-fractional-divider.h"52 53static inline u32 clk_fd_readl(struct clk_fractional_divider *fd)54{55 if (fd->flags & CLK_FRAC_DIVIDER_BIG_ENDIAN)56 return ioread32be(fd->reg);57 58 return readl(fd->reg);59}60 61static inline void clk_fd_writel(struct clk_fractional_divider *fd, u32 val)62{63 if (fd->flags & CLK_FRAC_DIVIDER_BIG_ENDIAN)64 iowrite32be(val, fd->reg);65 else66 writel(val, fd->reg);67}68 69static void clk_fd_get_div(struct clk_hw *hw, struct u32_fract *fract)70{71 struct clk_fractional_divider *fd = to_clk_fd(hw);72 unsigned long flags = 0;73 unsigned long m, n;74 u32 mmask, nmask;75 u32 val;76 77 if (fd->lock)78 spin_lock_irqsave(fd->lock, flags);79 else80 __acquire(fd->lock);81 82 val = clk_fd_readl(fd);83 84 if (fd->lock)85 spin_unlock_irqrestore(fd->lock, flags);86 else87 __release(fd->lock);88 89 mmask = GENMASK(fd->mwidth - 1, 0) << fd->mshift;90 nmask = GENMASK(fd->nwidth - 1, 0) << fd->nshift;91 92 m = (val & mmask) >> fd->mshift;93 n = (val & nmask) >> fd->nshift;94 95 if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {96 m++;97 n++;98 }99 100 fract->numerator = m;101 fract->denominator = n;102}103 104static unsigned long clk_fd_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)105{106 struct u32_fract fract;107 u64 ret;108 109 clk_fd_get_div(hw, &fract);110 111 if (!fract.numerator || !fract.denominator)112 return parent_rate;113 114 ret = (u64)parent_rate * fract.numerator;115 do_div(ret, fract.denominator);116 117 return ret;118}119 120void clk_fractional_divider_general_approximation(struct clk_hw *hw,121 unsigned long rate,122 unsigned long *parent_rate,123 unsigned long *m, unsigned long *n)124{125 struct clk_fractional_divider *fd = to_clk_fd(hw);126 unsigned long max_m, max_n;127 128 /*129 * Get rate closer to *parent_rate to guarantee there is no overflow130 * for m and n. In the result it will be the nearest rate left shifted131 * by (scale - fd->nwidth) bits.132 *133 * For the detailed explanation see the top comment in this file.134 */135 if (fd->flags & CLK_FRAC_DIVIDER_POWER_OF_TWO_PS) {136 unsigned long scale = fls_long(*parent_rate / rate - 1);137 138 if (scale > fd->nwidth)139 rate <<= scale - fd->nwidth;140 }141 142 if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {143 max_m = BIT(fd->mwidth);144 max_n = BIT(fd->nwidth);145 } else {146 max_m = GENMASK(fd->mwidth - 1, 0);147 max_n = GENMASK(fd->nwidth - 1, 0);148 }149 150 rational_best_approximation(rate, *parent_rate, max_m, max_n, m, n);151}152EXPORT_SYMBOL_GPL(clk_fractional_divider_general_approximation);153 154static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,155 unsigned long *parent_rate)156{157 struct clk_fractional_divider *fd = to_clk_fd(hw);158 unsigned long m, n;159 u64 ret;160 161 if (!rate || (!clk_hw_can_set_rate_parent(hw) && rate >= *parent_rate))162 return *parent_rate;163 164 if (fd->approximation)165 fd->approximation(hw, rate, parent_rate, &m, &n);166 else167 clk_fractional_divider_general_approximation(hw, rate, parent_rate, &m, &n);168 169 ret = (u64)*parent_rate * m;170 do_div(ret, n);171 172 return ret;173}174 175static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,176 unsigned long parent_rate)177{178 struct clk_fractional_divider *fd = to_clk_fd(hw);179 unsigned long flags = 0;180 unsigned long m, n, max_m, max_n;181 u32 mmask, nmask;182 u32 val;183 184 if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {185 max_m = BIT(fd->mwidth);186 max_n = BIT(fd->nwidth);187 } else {188 max_m = GENMASK(fd->mwidth - 1, 0);189 max_n = GENMASK(fd->nwidth - 1, 0);190 }191 rational_best_approximation(rate, parent_rate, max_m, max_n, &m, &n);192 193 if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {194 m--;195 n--;196 }197 198 mmask = GENMASK(fd->mwidth - 1, 0) << fd->mshift;199 nmask = GENMASK(fd->nwidth - 1, 0) << fd->nshift;200 201 if (fd->lock)202 spin_lock_irqsave(fd->lock, flags);203 else204 __acquire(fd->lock);205 206 val = clk_fd_readl(fd);207 val &= ~(mmask | nmask);208 val |= (m << fd->mshift) | (n << fd->nshift);209 clk_fd_writel(fd, val);210 211 if (fd->lock)212 spin_unlock_irqrestore(fd->lock, flags);213 else214 __release(fd->lock);215 216 return 0;217}218 219#ifdef CONFIG_DEBUG_FS220static int clk_fd_numerator_get(void *hw, u64 *val)221{222 struct u32_fract fract;223 224 clk_fd_get_div(hw, &fract);225 226 *val = fract.numerator;227 228 return 0;229}230DEFINE_DEBUGFS_ATTRIBUTE(clk_fd_numerator_fops, clk_fd_numerator_get, NULL, "%llu\n");231 232static int clk_fd_denominator_get(void *hw, u64 *val)233{234 struct u32_fract fract;235 236 clk_fd_get_div(hw, &fract);237 238 *val = fract.denominator;239 240 return 0;241}242DEFINE_DEBUGFS_ATTRIBUTE(clk_fd_denominator_fops, clk_fd_denominator_get, NULL, "%llu\n");243 244static void clk_fd_debug_init(struct clk_hw *hw, struct dentry *dentry)245{246 debugfs_create_file("numerator", 0444, dentry, hw, &clk_fd_numerator_fops);247 debugfs_create_file("denominator", 0444, dentry, hw, &clk_fd_denominator_fops);248}249#endif250 251const struct clk_ops clk_fractional_divider_ops = {252 .recalc_rate = clk_fd_recalc_rate,253 .round_rate = clk_fd_round_rate,254 .set_rate = clk_fd_set_rate,255#ifdef CONFIG_DEBUG_FS256 .debug_init = clk_fd_debug_init,257#endif258};259EXPORT_SYMBOL_GPL(clk_fractional_divider_ops);260 261struct clk_hw *clk_hw_register_fractional_divider(struct device *dev,262 const char *name, const char *parent_name, unsigned long flags,263 void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,264 u8 clk_divider_flags, spinlock_t *lock)265{266 struct clk_fractional_divider *fd;267 struct clk_init_data init;268 struct clk_hw *hw;269 int ret;270 271 fd = kzalloc(sizeof(*fd), GFP_KERNEL);272 if (!fd)273 return ERR_PTR(-ENOMEM);274 275 init.name = name;276 init.ops = &clk_fractional_divider_ops;277 init.flags = flags;278 init.parent_names = parent_name ? &parent_name : NULL;279 init.num_parents = parent_name ? 1 : 0;280 281 fd->reg = reg;282 fd->mshift = mshift;283 fd->mwidth = mwidth;284 fd->nshift = nshift;285 fd->nwidth = nwidth;286 fd->flags = clk_divider_flags;287 fd->lock = lock;288 fd->hw.init = &init;289 290 hw = &fd->hw;291 ret = clk_hw_register(dev, hw);292 if (ret) {293 kfree(fd);294 hw = ERR_PTR(ret);295 }296 297 return hw;298}299EXPORT_SYMBOL_GPL(clk_hw_register_fractional_divider);300 301struct clk *clk_register_fractional_divider(struct device *dev,302 const char *name, const char *parent_name, unsigned long flags,303 void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,304 u8 clk_divider_flags, spinlock_t *lock)305{306 struct clk_hw *hw;307 308 hw = clk_hw_register_fractional_divider(dev, name, parent_name, flags,309 reg, mshift, mwidth, nshift, nwidth, clk_divider_flags,310 lock);311 if (IS_ERR(hw))312 return ERR_CAST(hw);313 return hw->clk;314}315EXPORT_SYMBOL_GPL(clk_register_fractional_divider);316 317void clk_hw_unregister_fractional_divider(struct clk_hw *hw)318{319 struct clk_fractional_divider *fd;320 321 fd = to_clk_fd(hw);322 323 clk_hw_unregister(hw);324 kfree(fd);325}326