Merge branch 'for-linus' of git://brick.kernel.dk/data/git/linux-2.6-block
[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/config.h>
23 #include <linux/sched.h>
24 #include <linux/kernel.h>
25 #include <linux/smp.h>
26 #include <linux/cpu.h>
27 #include <linux/sysctl.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                                  system_state == SYSTEM_RUNNING)
39 #else
40 #define cpu_should_die()        0
41 #endif
42
43 /*
44  * The body of the idle task.
45  */
46 void cpu_idle(void)
47 {
48         if (ppc_md.idle_loop)
49                 ppc_md.idle_loop();     /* doesn't return */
50
51         set_thread_flag(TIF_POLLING_NRFLAG);
52         while (1) {
53                 while (!need_resched() && !cpu_should_die()) {
54                         ppc64_runlatch_off();
55
56                         if (ppc_md.power_save) {
57                                 clear_thread_flag(TIF_POLLING_NRFLAG);
58                                 /*
59                                  * smp_mb is so clearing of TIF_POLLING_NRFLAG
60                                  * is ordered w.r.t. need_resched() test.
61                                  */
62                                 smp_mb();
63                                 local_irq_disable();
64
65                                 /* check again after disabling irqs */
66                                 if (!need_resched() && !cpu_should_die())
67                                         ppc_md.power_save();
68
69                                 local_irq_enable();
70                                 set_thread_flag(TIF_POLLING_NRFLAG);
71
72                         } else {
73                                 /*
74                                  * Go into low thread priority and possibly
75                                  * low power mode.
76                                  */
77                                 HMT_low();
78                                 HMT_very_low();
79                         }
80                 }
81
82                 HMT_medium();
83                 ppc64_runlatch_on();
84                 if (cpu_should_die())
85                         cpu_die();
86                 preempt_enable_no_resched();
87                 schedule();
88                 preempt_disable();
89         }
90 }
91
92 int powersave_nap;
93
94 #ifdef CONFIG_SYSCTL
95 /*
96  * Register the sysctl to set/clear powersave_nap.
97  */
98 static ctl_table powersave_nap_ctl_table[]={
99         {
100                 .ctl_name       = KERN_PPC_POWERSAVE_NAP,
101                 .procname       = "powersave-nap",
102                 .data           = &powersave_nap,
103                 .maxlen         = sizeof(int),
104                 .mode           = 0644,
105                 .proc_handler   = &proc_dointvec,
106         },
107         { 0, },
108 };
109 static ctl_table powersave_nap_sysctl_root[] = {
110         { 1, "kernel", NULL, 0, 0755, powersave_nap_ctl_table, },
111         { 0,},
112 };
113
114 static int __init
115 register_powersave_nap_sysctl(void)
116 {
117         register_sysctl_table(powersave_nap_sysctl_root, 0);
118
119         return 0;
120 }
121 __initcall(register_powersave_nap_sysctl);
122 #endif