avr32: Scale loops_per_jiffy when cpu frequency changes
[linux-2.6.git] / arch / avr32 / mach-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 <asm/system.h>
22
23 static struct clk *cpuclk;
24
25 static int at32_verify_speed(struct cpufreq_policy *policy)
26 {
27         if (policy->cpu != 0)
28                 return -EINVAL;
29
30         cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
31                         policy->cpuinfo.max_freq);
32         return 0;
33 }
34
35 static unsigned int at32_get_speed(unsigned int cpu)
36 {
37         /* No SMP support */
38         if (cpu)
39                 return 0;
40         return (unsigned int)((clk_get_rate(cpuclk) + 500) / 1000);
41 }
42
43 static unsigned int     ref_freq;
44 static unsigned long    loops_per_jiffy_ref;
45
46 static int at32_set_target(struct cpufreq_policy *policy,
47                           unsigned int target_freq,
48                           unsigned int relation)
49 {
50         struct cpufreq_freqs freqs;
51         long freq;
52
53         /* Convert target_freq from kHz to Hz */
54         freq = clk_round_rate(cpuclk, target_freq * 1000);
55
56         /* Check if policy->min <= new_freq <= policy->max */
57         if(freq < (policy->min * 1000) || freq > (policy->max * 1000))
58                 return -EINVAL;
59
60         pr_debug("cpufreq: requested frequency %u Hz\n", target_freq * 1000);
61
62         freqs.old = at32_get_speed(0);
63         freqs.new = (freq + 500) / 1000;
64         freqs.cpu = 0;
65         freqs.flags = 0;
66
67         if (!ref_freq) {
68                 ref_freq = freqs.old;
69                 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
70         }
71
72         cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
73         if (freqs.old < freqs.new)
74                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
75                                 loops_per_jiffy_ref, ref_freq, freqs.new);
76         clk_set_rate(cpuclk, freq);
77         if (freqs.new < freqs.old)
78                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
79                                 loops_per_jiffy_ref, ref_freq, freqs.new);
80         cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
81
82         pr_debug("cpufreq: set frequency %lu Hz\n", freq);
83
84         return 0;
85 }
86
87 static int __init at32_cpufreq_driver_init(struct cpufreq_policy *policy)
88 {
89         if (policy->cpu != 0)
90                 return -EINVAL;
91
92         cpuclk = clk_get(NULL, "cpu");
93         if (IS_ERR(cpuclk)) {
94                 pr_debug("cpufreq: could not get CPU clk\n");
95                 return PTR_ERR(cpuclk);
96         }
97
98         policy->cpuinfo.min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
99         policy->cpuinfo.max_freq = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
100         policy->cpuinfo.transition_latency = 0;
101         policy->cur = at32_get_speed(0);
102         policy->min = policy->cpuinfo.min_freq;
103         policy->max = policy->cpuinfo.max_freq;
104
105         printk("cpufreq: AT32AP CPU frequency driver\n");
106
107         return 0;
108 }
109
110 static struct cpufreq_driver at32_driver = {
111         .name           = "at32ap",
112         .owner          = THIS_MODULE,
113         .init           = at32_cpufreq_driver_init,
114         .verify         = at32_verify_speed,
115         .target         = at32_set_target,
116         .get            = at32_get_speed,
117         .flags          = CPUFREQ_STICKY,
118 };
119
120 static int __init at32_cpufreq_init(void)
121 {
122         return cpufreq_register_driver(&at32_driver);
123 }
124 late_initcall(at32_cpufreq_init);