1 /* 2 * Copyright (C) 2014 Intel Corporation 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 * 8 * Adjustable fractional divider clock implementation. 9 * Output rate = (m / n) * parent_rate. 10 * Uses rational best approximation algorithm. 11 */ 12 13 #include <linux/clk-provider.h> 14 #include <linux/module.h> 15 #include <linux/device.h> 16 #include <linux/slab.h> 17 #include <linux/rational.h> 18 19 #define to_clk_fd(_hw) container_of(_hw, struct clk_fractional_divider, hw) 20 21 static unsigned long clk_fd_recalc_rate(struct clk_hw *hw, 22 unsigned long parent_rate) 23 { 24 struct clk_fractional_divider *fd = to_clk_fd(hw); 25 unsigned long flags = 0; 26 unsigned long m, n; 27 u32 val; 28 u64 ret; 29 30 if (fd->lock) 31 spin_lock_irqsave(fd->lock, flags); 32 else 33 __acquire(fd->lock); 34 35 val = clk_readl(fd->reg); 36 37 if (fd->lock) 38 spin_unlock_irqrestore(fd->lock, flags); 39 else 40 __release(fd->lock); 41 42 m = (val & fd->mmask) >> fd->mshift; 43 n = (val & fd->nmask) >> fd->nshift; 44 45 if (!n || !m) 46 return parent_rate; 47 48 ret = (u64)parent_rate * m; 49 do_div(ret, n); 50 51 return ret; 52 } 53 54 static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate, 55 unsigned long *parent_rate) 56 { 57 struct clk_fractional_divider *fd = to_clk_fd(hw); 58 unsigned long scale; 59 unsigned long m, n; 60 u64 ret; 61 62 if (!rate || rate >= *parent_rate) 63 return *parent_rate; 64 65 /* 66 * Get rate closer to *parent_rate to guarantee there is no overflow 67 * for m and n. In the result it will be the nearest rate left shifted 68 * by (scale - fd->nwidth) bits. 69 */ 70 scale = fls_long(*parent_rate / rate - 1); 71 if (scale > fd->nwidth) 72 rate <<= scale - fd->nwidth; 73 74 rational_best_approximation(rate, *parent_rate, 75 GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0), 76 &m, &n); 77 78 ret = (u64)*parent_rate * m; 79 do_div(ret, n); 80 81 return ret; 82 } 83 84 static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate, 85 unsigned long parent_rate) 86 { 87 struct clk_fractional_divider *fd = to_clk_fd(hw); 88 unsigned long flags = 0; 89 unsigned long m, n; 90 u32 val; 91 92 rational_best_approximation(rate, parent_rate, 93 GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0), 94 &m, &n); 95 96 if (fd->lock) 97 spin_lock_irqsave(fd->lock, flags); 98 else 99 __acquire(fd->lock); 100 101 val = clk_readl(fd->reg); 102 val &= ~(fd->mmask | fd->nmask); 103 val |= (m << fd->mshift) | (n << fd->nshift); 104 clk_writel(val, fd->reg); 105 106 if (fd->lock) 107 spin_unlock_irqrestore(fd->lock, flags); 108 else 109 __release(fd->lock); 110 111 return 0; 112 } 113 114 const struct clk_ops clk_fractional_divider_ops = { 115 .recalc_rate = clk_fd_recalc_rate, 116 .round_rate = clk_fd_round_rate, 117 .set_rate = clk_fd_set_rate, 118 }; 119 EXPORT_SYMBOL_GPL(clk_fractional_divider_ops); 120 121 struct clk *clk_register_fractional_divider(struct device *dev, 122 const char *name, const char *parent_name, unsigned long flags, 123 void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth, 124 u8 clk_divider_flags, spinlock_t *lock) 125 { 126 struct clk_fractional_divider *fd; 127 struct clk_init_data init; 128 struct clk *clk; 129 130 fd = kzalloc(sizeof(*fd), GFP_KERNEL); 131 if (!fd) 132 return ERR_PTR(-ENOMEM); 133 134 init.name = name; 135 init.ops = &clk_fractional_divider_ops; 136 init.flags = flags | CLK_IS_BASIC; 137 init.parent_names = parent_name ? &parent_name : NULL; 138 init.num_parents = parent_name ? 1 : 0; 139 140 fd->reg = reg; 141 fd->mshift = mshift; 142 fd->mwidth = mwidth; 143 fd->mmask = GENMASK(mwidth - 1, 0) << mshift; 144 fd->nshift = nshift; 145 fd->nwidth = nwidth; 146 fd->nmask = GENMASK(nwidth - 1, 0) << nshift; 147 fd->flags = clk_divider_flags; 148 fd->lock = lock; 149 fd->hw.init = &init; 150 151 clk = clk_register(dev, &fd->hw); 152 if (IS_ERR(clk)) 153 kfree(fd); 154 155 return clk; 156 } 157 EXPORT_SYMBOL_GPL(clk_register_fractional_divider); 158