1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/types.h>
3 #include <linux/errno.h>
4 #include <linux/kernel.h>
5 #include <linux/delay.h>
6 #include <linux/slab.h>
7 #include <linux/init.h>
8 #include <linux/wait.h>
9 #include <linux/cpufreq.h>
10 
11 #include <asm/prom.h>
12 
13 #include "windfarm.h"
14 
15 #define VERSION "0.3"
16 
17 static int clamped;
18 static struct wf_control *clamp_control;
19 
20 static int clamp_notifier_call(struct notifier_block *self,
21 			       unsigned long event, void *data)
22 {
23 	struct cpufreq_policy *p = data;
24 	unsigned long max_freq;
25 
26 	if (event != CPUFREQ_ADJUST)
27 		return 0;
28 
29 	max_freq = clamped ? (p->cpuinfo.min_freq) : (p->cpuinfo.max_freq);
30 	cpufreq_verify_within_limits(p, 0, max_freq);
31 
32 	return 0;
33 }
34 
35 static struct notifier_block clamp_notifier = {
36 	.notifier_call = clamp_notifier_call,
37 };
38 
39 static int clamp_set(struct wf_control *ct, s32 value)
40 {
41 	if (value)
42 		printk(KERN_INFO "windfarm: Clamping CPU frequency to "
43 		       "minimum !\n");
44 	else
45 		printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
46 	clamped = value;
47 	cpufreq_update_policy(0);
48 	return 0;
49 }
50 
51 static int clamp_get(struct wf_control *ct, s32 *value)
52 {
53 	*value = clamped;
54 	return 0;
55 }
56 
57 static s32 clamp_min(struct wf_control *ct)
58 {
59 	return 0;
60 }
61 
62 static s32 clamp_max(struct wf_control *ct)
63 {
64 	return 1;
65 }
66 
67 static const struct wf_control_ops clamp_ops = {
68 	.set_value	= clamp_set,
69 	.get_value	= clamp_get,
70 	.get_min	= clamp_min,
71 	.get_max	= clamp_max,
72 	.owner		= THIS_MODULE,
73 };
74 
75 static int __init wf_cpufreq_clamp_init(void)
76 {
77 	struct wf_control *clamp;
78 
79 	clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
80 	if (clamp == NULL)
81 		return -ENOMEM;
82 	cpufreq_register_notifier(&clamp_notifier, CPUFREQ_POLICY_NOTIFIER);
83 	clamp->ops = &clamp_ops;
84 	clamp->name = "cpufreq-clamp";
85 	if (wf_register_control(clamp))
86 		goto fail;
87 	clamp_control = clamp;
88 	return 0;
89  fail:
90 	kfree(clamp);
91 	return -ENODEV;
92 }
93 
94 static void __exit wf_cpufreq_clamp_exit(void)
95 {
96 	if (clamp_control)
97 		wf_unregister_control(clamp_control);
98 }
99 
100 
101 module_init(wf_cpufreq_clamp_init);
102 module_exit(wf_cpufreq_clamp_exit);
103 
104 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
105 MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
106 MODULE_LICENSE("GPL");
107 
108