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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 | static unsigned long clk_fd_recalc_rate(struct clk_hw *hw, | |
20 | unsigned long parent_rate) | |
21 | { | |
22 | struct clk_fractional_divider *fd = to_clk_fd(hw); | |
23 | unsigned long flags = 0; | |
24 | unsigned long m, n; | |
25 | u32 val; | |
26 | u64 ret; | |
27 | ||
28 | if (fd->lock) | |
29 | spin_lock_irqsave(fd->lock, flags); | |
30 | else | |
31 | __acquire(fd->lock); | |
32 | ||
33 | val = clk_readl(fd->reg); | |
34 | ||
35 | if (fd->lock) | |
36 | spin_unlock_irqrestore(fd->lock, flags); | |
37 | else | |
38 | __release(fd->lock); | |
39 | ||
40 | m = (val & fd->mmask) >> fd->mshift; | |
41 | n = (val & fd->nmask) >> fd->nshift; | |
42 | ||
43 | if (!n || !m) | |
44 | return parent_rate; | |
45 | ||
46 | ret = (u64)parent_rate * m; | |
47 | do_div(ret, n); | |
48 | ||
49 | return ret; | |
50 | } | |
51 | ||
52 | static void clk_fd_general_approximation(struct clk_hw *hw, unsigned long rate, | |
53 | unsigned long *parent_rate, | |
54 | unsigned long *m, unsigned long *n) | |
55 | { | |
56 | struct clk_fractional_divider *fd = to_clk_fd(hw); | |
57 | unsigned long scale; | |
58 | ||
59 | /* | |
60 | * Get rate closer to *parent_rate to guarantee there is no overflow | |
61 | * for m and n. In the result it will be the nearest rate left shifted | |
62 | * by (scale - fd->nwidth) bits. | |
63 | */ | |
64 | scale = fls_long(*parent_rate / rate - 1); | |
65 | if (scale > fd->nwidth) | |
66 | rate <<= scale - fd->nwidth; | |
67 | ||
68 | rational_best_approximation(rate, *parent_rate, | |
69 | GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0), | |
70 | m, n); | |
71 | } | |
72 | ||
73 | static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate, | |
74 | unsigned long *parent_rate) | |
75 | { | |
76 | struct clk_fractional_divider *fd = to_clk_fd(hw); | |
77 | unsigned long m, n; | |
78 | u64 ret; | |
79 | ||
80 | if (!rate || (!clk_hw_can_set_rate_parent(hw) && rate >= *parent_rate)) | |
81 | return *parent_rate; | |
82 | ||
83 | if (fd->approximation) | |
84 | fd->approximation(hw, rate, parent_rate, &m, &n); | |
85 | else | |
86 | clk_fd_general_approximation(hw, rate, parent_rate, &m, &n); | |
87 | ||
88 | ret = (u64)*parent_rate * m; | |
89 | do_div(ret, n); | |
90 | ||
91 | return ret; | |
92 | } | |
93 | ||
94 | static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate, | |
95 | unsigned long parent_rate) | |
96 | { | |
97 | struct clk_fractional_divider *fd = to_clk_fd(hw); | |
98 | unsigned long flags = 0; | |
99 | unsigned long m, n; | |
100 | u32 val; | |
101 | ||
102 | rational_best_approximation(rate, parent_rate, | |
103 | GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0), | |
104 | &m, &n); | |
105 | ||
106 | if (fd->lock) | |
107 | spin_lock_irqsave(fd->lock, flags); | |
108 | else | |
109 | __acquire(fd->lock); | |
110 | ||
111 | val = clk_readl(fd->reg); | |
112 | val &= ~(fd->mmask | fd->nmask); | |
113 | val |= (m << fd->mshift) | (n << fd->nshift); | |
114 | clk_writel(val, fd->reg); | |
115 | ||
116 | if (fd->lock) | |
117 | spin_unlock_irqrestore(fd->lock, flags); | |
118 | else | |
119 | __release(fd->lock); | |
120 | ||
121 | return 0; | |
122 | } | |
123 | ||
124 | const struct clk_ops clk_fractional_divider_ops = { | |
125 | .recalc_rate = clk_fd_recalc_rate, | |
126 | .round_rate = clk_fd_round_rate, | |
127 | .set_rate = clk_fd_set_rate, | |
128 | }; | |
129 | EXPORT_SYMBOL_GPL(clk_fractional_divider_ops); | |
130 | ||
131 | struct clk_hw *clk_hw_register_fractional_divider(struct device *dev, | |
132 | const char *name, const char *parent_name, unsigned long flags, | |
133 | void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth, | |
134 | u8 clk_divider_flags, spinlock_t *lock) | |
135 | { | |
136 | struct clk_fractional_divider *fd; | |
137 | struct clk_init_data init; | |
138 | struct clk_hw *hw; | |
139 | int ret; | |
140 | ||
141 | fd = kzalloc(sizeof(*fd), GFP_KERNEL); | |
142 | if (!fd) | |
143 | return ERR_PTR(-ENOMEM); | |
144 | ||
145 | init.name = name; | |
146 | init.ops = &clk_fractional_divider_ops; | |
147 | init.flags = flags | CLK_IS_BASIC; | |
148 | init.parent_names = parent_name ? &parent_name : NULL; | |
149 | init.num_parents = parent_name ? 1 : 0; | |
150 | ||
151 | fd->reg = reg; | |
152 | fd->mshift = mshift; | |
153 | fd->mwidth = mwidth; | |
154 | fd->mmask = GENMASK(mwidth - 1, 0) << mshift; | |
155 | fd->nshift = nshift; | |
156 | fd->nwidth = nwidth; | |
157 | fd->nmask = GENMASK(nwidth - 1, 0) << nshift; | |
158 | fd->flags = clk_divider_flags; | |
159 | fd->lock = lock; | |
160 | fd->hw.init = &init; | |
161 | ||
162 | hw = &fd->hw; | |
163 | ret = clk_hw_register(dev, hw); | |
164 | if (ret) { | |
165 | kfree(fd); | |
166 | hw = ERR_PTR(ret); | |
167 | } | |
168 | ||
169 | return hw; | |
170 | } | |
171 | EXPORT_SYMBOL_GPL(clk_hw_register_fractional_divider); | |
172 | ||
173 | struct clk *clk_register_fractional_divider(struct device *dev, | |
174 | const char *name, const char *parent_name, unsigned long flags, | |
175 | void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth, | |
176 | u8 clk_divider_flags, spinlock_t *lock) | |
177 | { | |
178 | struct clk_hw *hw; | |
179 | ||
180 | hw = clk_hw_register_fractional_divider(dev, name, parent_name, flags, | |
181 | reg, mshift, mwidth, nshift, nwidth, clk_divider_flags, | |
182 | lock); | |
183 | if (IS_ERR(hw)) | |
184 | return ERR_CAST(hw); | |
185 | return hw->clk; | |
186 | } | |
187 | EXPORT_SYMBOL_GPL(clk_register_fractional_divider); | |
188 | ||
189 | void clk_hw_unregister_fractional_divider(struct clk_hw *hw) | |
190 | { | |
191 | struct clk_fractional_divider *fd; | |
192 | ||
193 | fd = to_clk_fd(hw); | |
194 | ||
195 | clk_hw_unregister(hw); | |
196 | kfree(fd); | |
197 | } |