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
23struct 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};
29static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
30
31static 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(load: info->busy_spus, EXP, active: 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
46static 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(policy: info->policy, target_freq, CPUFREQ_RELATION_H);
59
60 delay = usecs_to_jiffies(u: info->poll_int);
61 schedule_delayed_work_on(cpu: info->policy->cpu, dwork: &info->work, delay);
62}
63
64static void spu_gov_init_work(struct spu_gov_info_struct *info)
65{
66 int delay = usecs_to_jiffies(u: info->poll_int);
67 INIT_DEFERRABLE_WORK(&info->work, spu_gov_work);
68 schedule_delayed_work_on(cpu: info->policy->cpu, dwork: &info->work, delay);
69}
70
71static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
72{
73 cancel_delayed_work_sync(dwork: &info->work);
74}
75
76static 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
107static 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
123static struct cpufreq_governor spu_governor = {
124 .name = "spudemand",
125 .start = spu_gov_start,
126 .stop = spu_gov_stop,
127 .owner = THIS_MODULE,
128};
129cpufreq_governor_init(spu_governor);
130cpufreq_governor_exit(spu_governor);
131
132MODULE_LICENSE("GPL");
133MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
134

source code of linux/arch/powerpc/platforms/cell/cpufreq_spudemand.c