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/pm_qos.h>
7 #include <linux/slab.h>
8 #include <linux/init.h>
9 #include <linux/wait.h>
10 #include <linux/cpu.h>
11 #include <linux/cpufreq.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 static struct freq_qos_request qos_req;
20 static unsigned int min_freq, max_freq;
21 
clamp_set(struct wf_control * ct,s32 value)22 static int clamp_set(struct wf_control *ct, s32 value)
23 {
24 	unsigned int freq;
25 
26 	if (value) {
27 		freq = min_freq;
28 		printk(KERN_INFO "windfarm: Clamping CPU frequency to "
29 		       "minimum !\n");
30 	} else {
31 		freq = max_freq;
32 		printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
33 	}
34 	clamped = value;
35 
36 	return freq_qos_update_request(&qos_req, freq);
37 }
38 
clamp_get(struct wf_control * ct,s32 * value)39 static int clamp_get(struct wf_control *ct, s32 *value)
40 {
41 	*value = clamped;
42 	return 0;
43 }
44 
clamp_min(struct wf_control * ct)45 static s32 clamp_min(struct wf_control *ct)
46 {
47 	return 0;
48 }
49 
clamp_max(struct wf_control * ct)50 static s32 clamp_max(struct wf_control *ct)
51 {
52 	return 1;
53 }
54 
55 static const struct wf_control_ops clamp_ops = {
56 	.set_value	= clamp_set,
57 	.get_value	= clamp_get,
58 	.get_min	= clamp_min,
59 	.get_max	= clamp_max,
60 	.owner		= THIS_MODULE,
61 };
62 
wf_cpufreq_clamp_init(void)63 static int __init wf_cpufreq_clamp_init(void)
64 {
65 	struct cpufreq_policy *policy;
66 	struct wf_control *clamp;
67 	struct device *dev;
68 	int ret;
69 
70 	policy = cpufreq_cpu_get(0);
71 	if (!policy) {
72 		pr_warn("%s: cpufreq policy not found cpu0\n", __func__);
73 		return -EPROBE_DEFER;
74 	}
75 
76 	min_freq = policy->cpuinfo.min_freq;
77 	max_freq = policy->cpuinfo.max_freq;
78 
79 	ret = freq_qos_add_request(&policy->constraints, &qos_req, FREQ_QOS_MAX,
80 				   max_freq);
81 
82 	cpufreq_cpu_put(policy);
83 
84 	if (ret < 0) {
85 		pr_err("%s: Failed to add freq constraint (%d)\n", __func__,
86 		       ret);
87 		return ret;
88 	}
89 
90 	dev = get_cpu_device(0);
91 	if (unlikely(!dev)) {
92 		pr_warn("%s: No cpu device for cpu0\n", __func__);
93 		ret = -ENODEV;
94 		goto fail;
95 	}
96 
97 	clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
98 	if (clamp == NULL) {
99 		ret = -ENOMEM;
100 		goto fail;
101 	}
102 
103 	clamp->ops = &clamp_ops;
104 	clamp->name = "cpufreq-clamp";
105 	ret = wf_register_control(clamp);
106 	if (ret)
107 		goto free;
108 
109 	clamp_control = clamp;
110 	return 0;
111 
112  free:
113 	kfree(clamp);
114  fail:
115 	freq_qos_remove_request(&qos_req);
116 	return ret;
117 }
118 
wf_cpufreq_clamp_exit(void)119 static void __exit wf_cpufreq_clamp_exit(void)
120 {
121 	if (clamp_control) {
122 		wf_unregister_control(clamp_control);
123 		freq_qos_remove_request(&qos_req);
124 	}
125 }
126 
127 
128 module_init(wf_cpufreq_clamp_init);
129 module_exit(wf_cpufreq_clamp_exit);
130 
131 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
132 MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
133 MODULE_LICENSE("GPL");
134 
135