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 <asm/prom.h>
14 
15 #include "windfarm.h"
16 
17 #define VERSION "0.3"
18 
19 static int clamped;
20 static struct wf_control *clamp_control;
21 static struct freq_qos_request qos_req;
22 static unsigned int min_freq, max_freq;
23 
24 static int clamp_set(struct wf_control *ct, s32 value)
25 {
26 	unsigned int freq;
27 
28 	if (value) {
29 		freq = min_freq;
30 		printk(KERN_INFO "windfarm: Clamping CPU frequency to "
31 		       "minimum !\n");
32 	} else {
33 		freq = max_freq;
34 		printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
35 	}
36 	clamped = value;
37 
38 	return freq_qos_update_request(&qos_req, freq);
39 }
40 
41 static int clamp_get(struct wf_control *ct, s32 *value)
42 {
43 	*value = clamped;
44 	return 0;
45 }
46 
47 static s32 clamp_min(struct wf_control *ct)
48 {
49 	return 0;
50 }
51 
52 static s32 clamp_max(struct wf_control *ct)
53 {
54 	return 1;
55 }
56 
57 static const struct wf_control_ops clamp_ops = {
58 	.set_value	= clamp_set,
59 	.get_value	= clamp_get,
60 	.get_min	= clamp_min,
61 	.get_max	= clamp_max,
62 	.owner		= THIS_MODULE,
63 };
64 
65 static int __init wf_cpufreq_clamp_init(void)
66 {
67 	struct cpufreq_policy *policy;
68 	struct wf_control *clamp;
69 	struct device *dev;
70 	int ret;
71 
72 	policy = cpufreq_cpu_get(0);
73 	if (!policy) {
74 		pr_warn("%s: cpufreq policy not found cpu0\n", __func__);
75 		return -EPROBE_DEFER;
76 	}
77 
78 	min_freq = policy->cpuinfo.min_freq;
79 	max_freq = policy->cpuinfo.max_freq;
80 
81 	ret = freq_qos_add_request(&policy->constraints, &qos_req, FREQ_QOS_MAX,
82 				   max_freq);
83 
84 	cpufreq_cpu_put(policy);
85 
86 	if (ret < 0) {
87 		pr_err("%s: Failed to add freq constraint (%d)\n", __func__,
88 		       ret);
89 		return ret;
90 	}
91 
92 	dev = get_cpu_device(0);
93 	if (unlikely(!dev)) {
94 		pr_warn("%s: No cpu device for cpu0\n", __func__);
95 		ret = -ENODEV;
96 		goto fail;
97 	}
98 
99 	clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
100 	if (clamp == NULL) {
101 		ret = -ENOMEM;
102 		goto fail;
103 	}
104 
105 	clamp->ops = &clamp_ops;
106 	clamp->name = "cpufreq-clamp";
107 	ret = wf_register_control(clamp);
108 	if (ret)
109 		goto free;
110 
111 	clamp_control = clamp;
112 	return 0;
113 
114  free:
115 	kfree(clamp);
116  fail:
117 	freq_qos_remove_request(&qos_req);
118 	return ret;
119 }
120 
121 static void __exit wf_cpufreq_clamp_exit(void)
122 {
123 	if (clamp_control) {
124 		wf_unregister_control(clamp_control);
125 		freq_qos_remove_request(&qos_req);
126 	}
127 }
128 
129 
130 module_init(wf_cpufreq_clamp_init);
131 module_exit(wf_cpufreq_clamp_exit);
132 
133 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
134 MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
135 MODULE_LICENSE("GPL");
136 
137