Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
[linux-2.6] / arch / powerpc / kernel / idle.c
1 /*
2  * Idle daemon for PowerPC.  Idle daemon will handle any action
3  * that needs to be taken when the system becomes idle.
4  *
5  * Originally written by Cort Dougan (cort@cs.nmt.edu).
6  * Subsequent 32-bit hacking by Tom Rini, Armin Kuster,
7  * Paul Mackerras and others.
8  *
9  * iSeries supported added by Mike Corrigan <mikejc@us.ibm.com>
10  *
11  * Additional shared processor, SMT, and firmware support
12  *    Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com>
13  *
14  * 32-bit and 64-bit versions merged by Paul Mackerras <paulus@samba.org>
15  *
16  * This program is free software; you can redistribute it and/or
17  * modify it under the terms of the GNU General Public License
18  * as published by the Free Software Foundation; either version
19  * 2 of the License, or (at your option) any later version.
20  */
21
22 #include <linux/sched.h>
23 #include <linux/kernel.h>
24 #include <linux/smp.h>
25 #include <linux/cpu.h>
26 #include <linux/sysctl.h>
27 #include <linux/tick.h>
28
29 #include <asm/system.h>
30 #include <asm/processor.h>
31 #include <asm/cputable.h>
32 #include <asm/time.h>
33 #include <asm/machdep.h>
34 #include <asm/smp.h>
35
36 #ifdef CONFIG_HOTPLUG_CPU
37 #define cpu_should_die()        cpu_is_offline(smp_processor_id())
38 #else
39 #define cpu_should_die()        0
40 #endif
41
42 static int __init powersave_off(char *arg)
43 {
44         ppc_md.power_save = NULL;
45         return 0;
46 }
47 __setup("powersave=off", powersave_off);
48
49 /*
50  * The body of the idle task.
51  */
52 void cpu_idle(void)
53 {
54         if (ppc_md.idle_loop)
55                 ppc_md.idle_loop();     /* doesn't return */
56
57         set_thread_flag(TIF_POLLING_NRFLAG);
58         while (1) {
59                 tick_nohz_stop_sched_tick(1);
60                 while (!need_resched() && !cpu_should_die()) {
61                         ppc64_runlatch_off();
62
63                         if (ppc_md.power_save) {
64                                 clear_thread_flag(TIF_POLLING_NRFLAG);
65                                 /*
66                                  * smp_mb is so clearing of TIF_POLLING_NRFLAG
67                                  * is ordered w.r.t. need_resched() test.
68                                  */
69                                 smp_mb();
70                                 local_irq_disable();
71
72                                 /* check again after disabling irqs */
73                                 if (!need_resched() && !cpu_should_die())
74                                         ppc_md.power_save();
75
76                                 local_irq_enable();
77                                 set_thread_flag(TIF_POLLING_NRFLAG);
78
79                         } else {
80                                 /*
81                                  * Go into low thread priority and possibly
82                                  * low power mode.
83                                  */
84                                 HMT_low();
85                                 HMT_very_low();
86                         }
87                 }
88
89                 HMT_medium();
90                 ppc64_runlatch_on();
91                 tick_nohz_restart_sched_tick();
92                 if (cpu_should_die())
93                         cpu_die();
94                 preempt_enable_no_resched();
95                 schedule();
96                 preempt_disable();
97         }
98 }
99
100 int powersave_nap;
101
102 #ifdef CONFIG_SYSCTL
103 /*
104  * Register the sysctl to set/clear powersave_nap.
105  */
106 static ctl_table powersave_nap_ctl_table[]={
107         {
108                 .ctl_name       = KERN_PPC_POWERSAVE_NAP,
109                 .procname       = "powersave-nap",
110                 .data           = &powersave_nap,
111                 .maxlen         = sizeof(int),
112                 .mode           = 0644,
113                 .proc_handler   = &proc_dointvec,
114         },
115         {}
116 };
117 static ctl_table powersave_nap_sysctl_root[] = {
118         {
119                 .ctl_name       = CTL_KERN,
120                 .procname       = "kernel",
121                 .mode           = 0555,
122                 .child          = powersave_nap_ctl_table,
123         },
124         {}
125 };
126
127 static int __init
128 register_powersave_nap_sysctl(void)
129 {
130         register_sysctl_table(powersave_nap_sysctl_root);
131
132         return 0;
133 }
134 __initcall(register_powersave_nap_sysctl);
135 #endif