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
powersave_off(char * arg)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 */
cpu_idle(void)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
do_nothing(void * unused)116 static void do_nothing(void *unused)
117 {
118 }
119
120 /*
121 * cpu_idle_wait - Used to ensure that all the CPUs come out of the old
122 * idle loop and start using the new idle loop.
123 * Required while changing idle handler on SMP systems.
124 * Caller must have changed idle handler to the new value before the call.
125 * This window may be larger on shared systems.
126 */
cpu_idle_wait(void)127 void cpu_idle_wait(void)
128 {
129 smp_mb();
130 /* kick all the CPUs so that they exit out of pm_idle */
131 smp_call_function(do_nothing, NULL, 1);
132 }
133 EXPORT_SYMBOL_GPL(cpu_idle_wait);
134
135 int powersave_nap;
136
137 #ifdef CONFIG_SYSCTL
138 /*
139 * Register the sysctl to set/clear powersave_nap.
140 */
141 static ctl_table powersave_nap_ctl_table[]={
142 {
143 .procname = "powersave-nap",
144 .data = &powersave_nap,
145 .maxlen = sizeof(int),
146 .mode = 0644,
147 .proc_handler = proc_dointvec,
148 },
149 {}
150 };
151 static ctl_table powersave_nap_sysctl_root[] = {
152 {
153 .procname = "kernel",
154 .mode = 0555,
155 .child = powersave_nap_ctl_table,
156 },
157 {}
158 };
159
160 static int __init
register_powersave_nap_sysctl(void)161 register_powersave_nap_sysctl(void)
162 {
163 register_sysctl_table(powersave_nap_sysctl_root);
164
165 return 0;
166 }
167 __initcall(register_powersave_nap_sysctl);
168 #endif
169