1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * spu aware cpufreq governor for the cell processor
4 *
5 * © Copyright IBM Corporation 2006-2008
6 *
7 * Author: Christian Krafft <krafft@de.ibm.com>
8 */
9
10 #include <linux/cpufreq.h>
11 #include <linux/sched.h>
12 #include <linux/sched/loadavg.h>
13 #include <linux/module.h>
14 #include <linux/timer.h>
15 #include <linux/workqueue.h>
16 #include <linux/atomic.h>
17 #include <asm/machdep.h>
18 #include <asm/spu.h>
19
20 #define POLL_TIME 100000 /* in µs */
21 #define EXP 753 /* exp(-1) in fixed-point */
22
23 struct spu_gov_info_struct {
24 unsigned long busy_spus; /* fixed-point */
25 struct cpufreq_policy *policy;
26 struct delayed_work work;
27 unsigned int poll_int; /* µs */
28 };
29 static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
30
calc_freq(struct spu_gov_info_struct * info)31 static int calc_freq(struct spu_gov_info_struct *info)
32 {
33 int cpu;
34 int busy_spus;
35
36 cpu = info->policy->cpu;
37 busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);
38
39 info->busy_spus = calc_load(info->busy_spus, EXP, busy_spus * FIXED_1);
40 pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
41 cpu, busy_spus, info->busy_spus);
42
43 return info->policy->max * info->busy_spus / FIXED_1;
44 }
45
spu_gov_work(struct work_struct * work)46 static void spu_gov_work(struct work_struct *work)
47 {
48 struct spu_gov_info_struct *info;
49 int delay;
50 unsigned long target_freq;
51
52 info = container_of(work, struct spu_gov_info_struct, work.work);
53
54 /* after cancel_delayed_work_sync we unset info->policy */
55 BUG_ON(info->policy == NULL);
56
57 target_freq = calc_freq(info);
58 __cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);
59
60 delay = usecs_to_jiffies(info->poll_int);
61 schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
62 }
63
spu_gov_init_work(struct spu_gov_info_struct * info)64 static void spu_gov_init_work(struct spu_gov_info_struct *info)
65 {
66 int delay = usecs_to_jiffies(info->poll_int);
67 INIT_DEFERRABLE_WORK(&info->work, spu_gov_work);
68 schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
69 }
70
spu_gov_cancel_work(struct spu_gov_info_struct * info)71 static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
72 {
73 cancel_delayed_work_sync(&info->work);
74 }
75
spu_gov_start(struct cpufreq_policy * policy)76 static int spu_gov_start(struct cpufreq_policy *policy)
77 {
78 unsigned int cpu = policy->cpu;
79 struct spu_gov_info_struct *info = &per_cpu(spu_gov_info, cpu);
80 struct spu_gov_info_struct *affected_info;
81 int i;
82
83 if (!cpu_online(cpu)) {
84 printk(KERN_ERR "cpu %d is not online\n", cpu);
85 return -EINVAL;
86 }
87
88 if (!policy->cur) {
89 printk(KERN_ERR "no cpu specified in policy\n");
90 return -EINVAL;
91 }
92
93 /* initialize spu_gov_info for all affected cpus */
94 for_each_cpu(i, policy->cpus) {
95 affected_info = &per_cpu(spu_gov_info, i);
96 affected_info->policy = policy;
97 }
98
99 info->poll_int = POLL_TIME;
100
101 /* setup timer */
102 spu_gov_init_work(info);
103
104 return 0;
105 }
106
spu_gov_stop(struct cpufreq_policy * policy)107 static void spu_gov_stop(struct cpufreq_policy *policy)
108 {
109 unsigned int cpu = policy->cpu;
110 struct spu_gov_info_struct *info = &per_cpu(spu_gov_info, cpu);
111 int i;
112
113 /* cancel timer */
114 spu_gov_cancel_work(info);
115
116 /* clean spu_gov_info for all affected cpus */
117 for_each_cpu (i, policy->cpus) {
118 info = &per_cpu(spu_gov_info, i);
119 info->policy = NULL;
120 }
121 }
122
123 static struct cpufreq_governor spu_governor = {
124 .name = "spudemand",
125 .start = spu_gov_start,
126 .stop = spu_gov_stop,
127 .owner = THIS_MODULE,
128 };
129
130 /*
131 * module init and destoy
132 */
133
spu_gov_init(void)134 static int __init spu_gov_init(void)
135 {
136 int ret;
137
138 ret = cpufreq_register_governor(&spu_governor);
139 if (ret)
140 printk(KERN_ERR "registration of governor failed\n");
141 return ret;
142 }
143
spu_gov_exit(void)144 static void __exit spu_gov_exit(void)
145 {
146 cpufreq_unregister_governor(&spu_governor);
147 }
148
149
150 module_init(spu_gov_init);
151 module_exit(spu_gov_exit);
152
153 MODULE_LICENSE("GPL");
154 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
155
156
