xref: /linux/arch/powerpc/kernel/idle.c (revision 4413e16d9d21673bb5048a2e542f1aaa00015c2e)
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/processor.h>
30 #include <asm/cputable.h>
31 #include <asm/time.h>
32 #include <asm/machdep.h>
33 #include <asm/runlatch.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 unsigned long cpuidle_disable = IDLE_NO_OVERRIDE;
43 EXPORT_SYMBOL(cpuidle_disable);
44 
45 static int __init powersave_off(char *arg)
46 {
47 	ppc_md.power_save = NULL;
48 	cpuidle_disable = IDLE_POWERSAVE_OFF;
49 	return 0;
50 }
51 __setup("powersave=off", powersave_off);
52 
53 /*
54  * The body of the idle task.
55  */
56 void cpu_idle(void)
57 {
58 	if (ppc_md.idle_loop)
59 		ppc_md.idle_loop();	/* doesn't return */
60 
61 	set_thread_flag(TIF_POLLING_NRFLAG);
62 	while (1) {
63 		tick_nohz_idle_enter();
64 		rcu_idle_enter();
65 
66 		while (!need_resched() && !cpu_should_die()) {
67 			ppc64_runlatch_off();
68 
69 			if (ppc_md.power_save) {
70 				clear_thread_flag(TIF_POLLING_NRFLAG);
71 				/*
72 				 * smp_mb is so clearing of TIF_POLLING_NRFLAG
73 				 * is ordered w.r.t. need_resched() test.
74 				 */
75 				smp_mb();
76 				local_irq_disable();
77 
78 				/* Don't trace irqs off for idle */
79 				stop_critical_timings();
80 
81 				/* check again after disabling irqs */
82 				if (!need_resched() && !cpu_should_die())
83 					ppc_md.power_save();
84 
85 				start_critical_timings();
86 
87 				/* Some power_save functions return with
88 				 * interrupts enabled, some don't.
89 				 */
90 				if (irqs_disabled())
91 					local_irq_enable();
92 				set_thread_flag(TIF_POLLING_NRFLAG);
93 
94 			} else {
95 				/*
96 				 * Go into low thread priority and possibly
97 				 * low power mode.
98 				 */
99 				HMT_low();
100 				HMT_very_low();
101 			}
102 		}
103 
104 		HMT_medium();
105 		ppc64_runlatch_on();
106 		rcu_idle_exit();
107 		tick_nohz_idle_exit();
108 		if (cpu_should_die()) {
109 			sched_preempt_enable_no_resched();
110 			cpu_die();
111 		}
112 		schedule_preempt_disabled();
113 	}
114 }
115 
116 int powersave_nap;
117 
118 #ifdef CONFIG_SYSCTL
119 /*
120  * Register the sysctl to set/clear powersave_nap.
121  */
122 static ctl_table powersave_nap_ctl_table[]={
123 	{
124 		.procname	= "powersave-nap",
125 		.data		= &powersave_nap,
126 		.maxlen		= sizeof(int),
127 		.mode		= 0644,
128 		.proc_handler	= proc_dointvec,
129 	},
130 	{}
131 };
132 static ctl_table powersave_nap_sysctl_root[] = {
133 	{
134 		.procname	= "kernel",
135 		.mode		= 0555,
136 		.child		= powersave_nap_ctl_table,
137 	},
138 	{}
139 };
140 
141 static int __init
142 register_powersave_nap_sysctl(void)
143 {
144 	register_sysctl_table(powersave_nap_sysctl_root);
145 
146 	return 0;
147 }
148 __initcall(register_powersave_nap_sysctl);
149 #endif
150