1/*
2 * spu aware cpufreq governor for the cell processor
3 *
4 * © Copyright IBM Corporation 2006-2008
5 *
6 * Author: Christian Krafft <krafft@de.ibm.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2, or (at your option)
11 * any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 */
22
23#include <linux/cpufreq.h>
24#include <linux/sched.h>
25#include <linux/module.h>
26#include <linux/timer.h>
27#include <linux/workqueue.h>
28#include <linux/atomic.h>
29#include <asm/machdep.h>
30#include <asm/spu.h>
31
32#define POLL_TIME	100000		/* in µs */
33#define EXP		753		/* exp(-1) in fixed-point */
34
35struct spu_gov_info_struct {
36	unsigned long busy_spus;	/* fixed-point */
37	struct cpufreq_policy *policy;
38	struct delayed_work work;
39	unsigned int poll_int;		/* µs */
40};
41static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
42
43static int calc_freq(struct spu_gov_info_struct *info)
44{
45	int cpu;
46	int busy_spus;
47
48	cpu = info->policy->cpu;
49	busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);
50
51	CALC_LOAD(info->busy_spus, EXP, busy_spus * FIXED_1);
52	pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
53			cpu, busy_spus, info->busy_spus);
54
55	return info->policy->max * info->busy_spus / FIXED_1;
56}
57
58static void spu_gov_work(struct work_struct *work)
59{
60	struct spu_gov_info_struct *info;
61	int delay;
62	unsigned long target_freq;
63
64	info = container_of(work, struct spu_gov_info_struct, work.work);
65
66	/* after cancel_delayed_work_sync we unset info->policy */
67	BUG_ON(info->policy == NULL);
68
69	target_freq = calc_freq(info);
70	__cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);
71
72	delay = usecs_to_jiffies(info->poll_int);
73	schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
74}
75
76static void spu_gov_init_work(struct spu_gov_info_struct *info)
77{
78	int delay = usecs_to_jiffies(info->poll_int);
79	INIT_DEFERRABLE_WORK(&info->work, spu_gov_work);
80	schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
81}
82
83static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
84{
85	cancel_delayed_work_sync(&info->work);
86}
87
88static int spu_gov_govern(struct cpufreq_policy *policy, unsigned int event)
89{
90	unsigned int cpu = policy->cpu;
91	struct spu_gov_info_struct *info, *affected_info;
92	int i;
93	int ret = 0;
94
95	info = &per_cpu(spu_gov_info, cpu);
96
97	switch (event) {
98	case CPUFREQ_GOV_START:
99		if (!cpu_online(cpu)) {
100			printk(KERN_ERR "cpu %d is not online\n", cpu);
101			ret = -EINVAL;
102			break;
103		}
104
105		if (!policy->cur) {
106			printk(KERN_ERR "no cpu specified in policy\n");
107			ret = -EINVAL;
108			break;
109		}
110
111		/* initialize spu_gov_info for all affected cpus */
112		for_each_cpu(i, policy->cpus) {
113			affected_info = &per_cpu(spu_gov_info, i);
114			affected_info->policy = policy;
115		}
116
117		info->poll_int = POLL_TIME;
118
119		/* setup timer */
120		spu_gov_init_work(info);
121
122		break;
123
124	case CPUFREQ_GOV_STOP:
125		/* cancel timer */
126		spu_gov_cancel_work(info);
127
128		/* clean spu_gov_info for all affected cpus */
129		for_each_cpu (i, policy->cpus) {
130			info = &per_cpu(spu_gov_info, i);
131			info->policy = NULL;
132		}
133
134		break;
135	}
136
137	return ret;
138}
139
140static struct cpufreq_governor spu_governor = {
141	.name = "spudemand",
142	.governor = spu_gov_govern,
143	.owner = THIS_MODULE,
144};
145
146/*
147 * module init and destoy
148 */
149
150static int __init spu_gov_init(void)
151{
152	int ret;
153
154	ret = cpufreq_register_governor(&spu_governor);
155	if (ret)
156		printk(KERN_ERR "registration of governor failed\n");
157	return ret;
158}
159
160static void __exit spu_gov_exit(void)
161{
162	cpufreq_unregister_governor(&spu_governor);
163}
164
165
166module_init(spu_gov_init);
167module_exit(spu_gov_exit);
168
169MODULE_LICENSE("GPL");
170MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
171
172