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  */
11 
12 #include <linux/clk-provider.h>
13 #include <linux/module.h>
14 #include <linux/device.h>
15 #include <linux/slab.h>
16 #include <linux/gcd.h>
17 
18 #define to_clk_fd(_hw) container_of(_hw, struct clk_fractional_divider, hw)
19 
20 static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
21 					unsigned long parent_rate)
22 {
23 	struct clk_fractional_divider *fd = to_clk_fd(hw);
24 	unsigned long flags = 0;
25 	u32 val, m, n;
26 	u64 ret;
27 
28 	if (fd->lock)
29 		spin_lock_irqsave(fd->lock, flags);
30 
31 	val = clk_readl(fd->reg);
32 
33 	if (fd->lock)
34 		spin_unlock_irqrestore(fd->lock, flags);
35 
36 	m = (val & fd->mmask) >> fd->mshift;
37 	n = (val & fd->nmask) >> fd->nshift;
38 
39 	if (!n || !m)
40 		return parent_rate;
41 
42 	ret = (u64)parent_rate * m;
43 	do_div(ret, n);
44 
45 	return ret;
46 }
47 
48 static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
49 			      unsigned long *prate)
50 {
51 	struct clk_fractional_divider *fd = to_clk_fd(hw);
52 	unsigned maxn = (fd->nmask >> fd->nshift) + 1;
53 	unsigned div;
54 
55 	if (!rate || rate >= *prate)
56 		return *prate;
57 
58 	div = gcd(*prate, rate);
59 
60 	while ((*prate / div) > maxn) {
61 		div <<= 1;
62 		rate <<= 1;
63 	}
64 
65 	return rate;
66 }
67 
68 static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,
69 			   unsigned long parent_rate)
70 {
71 	struct clk_fractional_divider *fd = to_clk_fd(hw);
72 	unsigned long flags = 0;
73 	unsigned long div;
74 	unsigned n, m;
75 	u32 val;
76 
77 	div = gcd(parent_rate, rate);
78 	m = rate / div;
79 	n = parent_rate / div;
80 
81 	if (fd->lock)
82 		spin_lock_irqsave(fd->lock, flags);
83 
84 	val = clk_readl(fd->reg);
85 	val &= ~(fd->mmask | fd->nmask);
86 	val |= (m << fd->mshift) | (n << fd->nshift);
87 	clk_writel(val, fd->reg);
88 
89 	if (fd->lock)
90 		spin_unlock_irqrestore(fd->lock, flags);
91 
92 	return 0;
93 }
94 
95 const struct clk_ops clk_fractional_divider_ops = {
96 	.recalc_rate = clk_fd_recalc_rate,
97 	.round_rate = clk_fd_round_rate,
98 	.set_rate = clk_fd_set_rate,
99 };
100 EXPORT_SYMBOL_GPL(clk_fractional_divider_ops);
101 
102 struct clk *clk_register_fractional_divider(struct device *dev,
103 		const char *name, const char *parent_name, unsigned long flags,
104 		void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
105 		u8 clk_divider_flags, spinlock_t *lock)
106 {
107 	struct clk_fractional_divider *fd;
108 	struct clk_init_data init;
109 	struct clk *clk;
110 
111 	fd = kzalloc(sizeof(*fd), GFP_KERNEL);
112 	if (!fd) {
113 		dev_err(dev, "could not allocate fractional divider clk\n");
114 		return ERR_PTR(-ENOMEM);
115 	}
116 
117 	init.name = name;
118 	init.ops = &clk_fractional_divider_ops;
119 	init.flags = flags | CLK_IS_BASIC;
120 	init.parent_names = parent_name ? &parent_name : NULL;
121 	init.num_parents = parent_name ? 1 : 0;
122 
123 	fd->reg = reg;
124 	fd->mshift = mshift;
125 	fd->mmask = (BIT(mwidth) - 1) << mshift;
126 	fd->nshift = nshift;
127 	fd->nmask = (BIT(nwidth) - 1) << nshift;
128 	fd->flags = clk_divider_flags;
129 	fd->lock = lock;
130 	fd->hw.init = &init;
131 
132 	clk = clk_register(dev, &fd->hw);
133 	if (IS_ERR(clk))
134 		kfree(fd);
135 
136 	return clk;
137 }
138 EXPORT_SYMBOL_GPL(clk_register_fractional_divider);
139