1 /*
2 * Copyright (C) 2012 ST Microelectronics
3 * Viresh Kumar <vireshk@kernel.org>
4 *
5 * This file is licensed under the terms of the GNU General Public
6 * License version 2. This program is licensed "as is" without any
7 * warranty of any kind, whether express or implied.
8 *
9 * Fractional Synthesizer clock implementation
10 */
11
12 #define pr_fmt(fmt) "clk-frac-synth: " fmt
13
14 #include <linux/clk-provider.h>
15 #include <linux/slab.h>
16 #include <linux/io.h>
17 #include <linux/err.h>
18 #include "clk.h"
19
20 #define DIV_FACTOR_MASK 0x1FFFF
21
22 /*
23 * DOC: Fractional Synthesizer clock
24 *
25 * Fout from synthesizer can be given from below equation:
26 *
27 * Fout= Fin/2*div (division factor)
28 * div is 17 bits:-
29 * 0-13 (fractional part)
30 * 14-16 (integer part)
31 * div is (16-14 bits).(13-0 bits) (in binary)
32 *
33 * Fout = Fin/(2 * div)
34 * Fout = ((Fin / 10000)/(2 * div)) * 10000
35 * Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000
36 * Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000
37 *
38 * div << 14 simply 17 bit value written at register.
39 * Max error due to scaling down by 10000 is 10 KHz
40 */
41
42 #define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw)
43
frac_calc_rate(struct clk_hw * hw,unsigned long prate,int index)44 static unsigned long frac_calc_rate(struct clk_hw *hw, unsigned long prate,
45 int index)
46 {
47 struct clk_frac *frac = to_clk_frac(hw);
48 struct frac_rate_tbl *rtbl = frac->rtbl;
49
50 prate /= 10000;
51 prate <<= 14;
52 prate /= (2 * rtbl[index].div);
53 prate *= 10000;
54
55 return prate;
56 }
57
clk_frac_round_rate(struct clk_hw * hw,unsigned long drate,unsigned long * prate)58 static long clk_frac_round_rate(struct clk_hw *hw, unsigned long drate,
59 unsigned long *prate)
60 {
61 struct clk_frac *frac = to_clk_frac(hw);
62 int unused;
63
64 return clk_round_rate_index(hw, drate, *prate, frac_calc_rate,
65 frac->rtbl_cnt, &unused);
66 }
67
clk_frac_recalc_rate(struct clk_hw * hw,unsigned long parent_rate)68 static unsigned long clk_frac_recalc_rate(struct clk_hw *hw,
69 unsigned long parent_rate)
70 {
71 struct clk_frac *frac = to_clk_frac(hw);
72 unsigned long flags = 0;
73 unsigned int div = 1, val;
74
75 if (frac->lock)
76 spin_lock_irqsave(frac->lock, flags);
77
78 val = readl_relaxed(frac->reg);
79
80 if (frac->lock)
81 spin_unlock_irqrestore(frac->lock, flags);
82
83 div = val & DIV_FACTOR_MASK;
84
85 if (!div)
86 return 0;
87
88 parent_rate = parent_rate / 10000;
89
90 parent_rate = (parent_rate << 14) / (2 * div);
91 return parent_rate * 10000;
92 }
93
94 /* Configures new clock rate of frac */
clk_frac_set_rate(struct clk_hw * hw,unsigned long drate,unsigned long prate)95 static int clk_frac_set_rate(struct clk_hw *hw, unsigned long drate,
96 unsigned long prate)
97 {
98 struct clk_frac *frac = to_clk_frac(hw);
99 struct frac_rate_tbl *rtbl = frac->rtbl;
100 unsigned long flags = 0, val;
101 int i;
102
103 clk_round_rate_index(hw, drate, prate, frac_calc_rate, frac->rtbl_cnt,
104 &i);
105
106 if (frac->lock)
107 spin_lock_irqsave(frac->lock, flags);
108
109 val = readl_relaxed(frac->reg) & ~DIV_FACTOR_MASK;
110 val |= rtbl[i].div & DIV_FACTOR_MASK;
111 writel_relaxed(val, frac->reg);
112
113 if (frac->lock)
114 spin_unlock_irqrestore(frac->lock, flags);
115
116 return 0;
117 }
118
119 static const struct clk_ops clk_frac_ops = {
120 .recalc_rate = clk_frac_recalc_rate,
121 .round_rate = clk_frac_round_rate,
122 .set_rate = clk_frac_set_rate,
123 };
124
clk_register_frac(const char * name,const char * parent_name,unsigned long flags,void __iomem * reg,struct frac_rate_tbl * rtbl,u8 rtbl_cnt,spinlock_t * lock)125 struct clk *clk_register_frac(const char *name, const char *parent_name,
126 unsigned long flags, void __iomem *reg,
127 struct frac_rate_tbl *rtbl, u8 rtbl_cnt, spinlock_t *lock)
128 {
129 struct clk_init_data init;
130 struct clk_frac *frac;
131 struct clk *clk;
132
133 if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) {
134 pr_err("Invalid arguments passed\n");
135 return ERR_PTR(-EINVAL);
136 }
137
138 frac = kzalloc(sizeof(*frac), GFP_KERNEL);
139 if (!frac)
140 return ERR_PTR(-ENOMEM);
141
142 /* struct clk_frac assignments */
143 frac->reg = reg;
144 frac->rtbl = rtbl;
145 frac->rtbl_cnt = rtbl_cnt;
146 frac->lock = lock;
147 frac->hw.init = &init;
148
149 init.name = name;
150 init.ops = &clk_frac_ops;
151 init.flags = flags;
152 init.parent_names = &parent_name;
153 init.num_parents = 1;
154
155 clk = clk_register(NULL, &frac->hw);
156 if (!IS_ERR_OR_NULL(clk))
157 return clk;
158
159 pr_err("clk register failed\n");
160 kfree(frac);
161
162 return NULL;
163 }
164