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[mirror_ubuntu-zesty-kernel.git] / drivers / cpufreq / at32ap-cpufreq.c
1 /*
2 * Copyright (C) 2004-2007 Atmel Corporation
3 *
4 * Based on MIPS implementation arch/mips/kernel/time.c
5 * Copyright 2001 MontaVista Software Inc.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12 /*#define DEBUG*/
13
14 #include <linux/kernel.h>
15 #include <linux/types.h>
16 #include <linux/init.h>
17 #include <linux/cpufreq.h>
18 #include <linux/io.h>
19 #include <linux/clk.h>
20 #include <linux/err.h>
21 #include <linux/export.h>
22 #include <linux/slab.h>
23
24 static struct cpufreq_frequency_table *freq_table;
25
26 static unsigned int ref_freq;
27 static unsigned long loops_per_jiffy_ref;
28
29 static int at32_set_target(struct cpufreq_policy *policy, unsigned int index)
30 {
31 unsigned int old_freq, new_freq;
32
33 old_freq = policy->cur;
34 new_freq = freq_table[index].frequency;
35
36 if (!ref_freq) {
37 ref_freq = old_freq;
38 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
39 }
40
41 if (old_freq < new_freq)
42 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
43 loops_per_jiffy_ref, ref_freq, new_freq);
44 clk_set_rate(policy->clk, new_freq * 1000);
45 if (new_freq < old_freq)
46 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
47 loops_per_jiffy_ref, ref_freq, new_freq);
48
49 return 0;
50 }
51
52 static int at32_cpufreq_driver_init(struct cpufreq_policy *policy)
53 {
54 unsigned int frequency, rate, min_freq;
55 struct clk *cpuclk;
56 int retval, steps, i;
57
58 if (policy->cpu != 0)
59 return -EINVAL;
60
61 cpuclk = clk_get(NULL, "cpu");
62 if (IS_ERR(cpuclk)) {
63 pr_debug("cpufreq: could not get CPU clk\n");
64 retval = PTR_ERR(cpuclk);
65 goto out_err;
66 }
67
68 min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
69 frequency = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
70 policy->cpuinfo.transition_latency = 0;
71
72 /*
73 * AVR32 CPU frequency rate scales in power of two between maximum and
74 * minimum, also add space for the table end marker.
75 *
76 * Further validate that the frequency is usable, and append it to the
77 * frequency table.
78 */
79 steps = fls(frequency / min_freq) + 1;
80 freq_table = kzalloc(steps * sizeof(struct cpufreq_frequency_table),
81 GFP_KERNEL);
82 if (!freq_table) {
83 retval = -ENOMEM;
84 goto out_err_put_clk;
85 }
86
87 for (i = 0; i < (steps - 1); i++) {
88 rate = clk_round_rate(cpuclk, frequency * 1000) / 1000;
89
90 if (rate != frequency)
91 freq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
92 else
93 freq_table[i].frequency = frequency;
94
95 frequency /= 2;
96 }
97
98 policy->clk = cpuclk;
99 freq_table[steps - 1].frequency = CPUFREQ_TABLE_END;
100
101 retval = cpufreq_table_validate_and_show(policy, freq_table);
102 if (!retval) {
103 printk("cpufreq: AT32AP CPU frequency driver\n");
104 return 0;
105 }
106
107 kfree(freq_table);
108 out_err_put_clk:
109 clk_put(cpuclk);
110 out_err:
111 return retval;
112 }
113
114 static struct cpufreq_driver at32_driver = {
115 .name = "at32ap",
116 .init = at32_cpufreq_driver_init,
117 .verify = cpufreq_generic_frequency_table_verify,
118 .target_index = at32_set_target,
119 .get = cpufreq_generic_get,
120 .flags = CPUFREQ_STICKY,
121 };
122
123 static int __init at32_cpufreq_init(void)
124 {
125 return cpufreq_register_driver(&at32_driver);
126 }
127 late_initcall(at32_cpufreq_init);