1 /*
2  * Copyright (C) 2012 ST Microelectronics
3  * Viresh Kumar <viresh.linux@gmail.com>
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 
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 
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 
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 */
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 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 
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");
135 		return ERR_PTR(-EINVAL);
136 	}
137 
138 	frac = kzalloc(sizeof(*frac), GFP_KERNEL);
139 	if (!frac) {
140 		pr_err("could not allocate frac clk\n");
141 		return ERR_PTR(-ENOMEM);
142 	}
143 
144 	/* struct clk_frac assignments */
145 	frac->reg = reg;
146 	frac->rtbl = rtbl;
147 	frac->rtbl_cnt = rtbl_cnt;
148 	frac->lock = lock;
149 	frac->hw.init = &init;
150 
151 	init.name = name;
152 	init.ops = &clk_frac_ops;
153 	init.flags = flags;
154 	init.parent_names = &parent_name;
155 	init.num_parents = 1;
156 
157 	clk = clk_register(NULL, &frac->hw);
158 	if (!IS_ERR_OR_NULL(clk))
159 		return clk;
160 
161 	pr_err("clk register failed\n");
162 	kfree(frac);
163 
164 	return NULL;
165 }
166