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/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         set_thread_flag(TIF_POLLING_NRFLAG);
  59         while (1) {
  60                 tick_nohz_idle_enter();
  61                 rcu_idle_enter();
  62
  63                 while (!need_resched() && !cpu_should_die()) {
  64                         ppc64_runlatch_off();
  65
  66                         if (ppc_md.power_save) {
  67                                 clear_thread_flag(TIF_POLLING_NRFLAG);
  68                                 /*
  69                                  * smp_mb is so clearing of TIF_POLLING_NRFLAG
  70                                  * is ordered w.r.t. need_resched() test.
  71                                  */
  72                                 smp_mb();
  73                                 local_irq_disable();
  74
  75                                 /* Don't trace irqs off for idle */
  76                                 stop_critical_timings();
  77
  78                                 /* check again after disabling irqs */
  79                                 if (!need_resched() && !cpu_should_die())
  80                                         ppc_md.power_save();
  81
  82                                 start_critical_timings();
  83
  84                                 /* Some power_save functions return with
  85                                  * interrupts enabled, some don't.
  86                                  */
  87                                 if (irqs_disabled())
  88                                         local_irq_enable();
  89                                 set_thread_flag(TIF_POLLING_NRFLAG);
  90
  91                         } else {
  92                                 /*
  93                                  * Go into low thread priority and possibly
  94                                  * low power mode.
  95                                  */
  96                                 HMT_low();
  97                                 HMT_very_low();
  98                         }
  99                 }
 100
 101                 HMT_medium();
 102                 ppc64_runlatch_on();
 103                 rcu_idle_exit();
 104                 tick_nohz_idle_exit();
 105                 if (cpu_should_die()) {
 106                         sched_preempt_enable_no_resched();
 107                         cpu_die();
 108                 }
 109                 schedule_preempt_disabled();
 110         }
 111 }
 112
 113 int powersave_nap;
 114
 115 #ifdef CONFIG_SYSCTL
 116 /*
 117  * Register the sysctl to set/clear powersave_nap.
 118  */
 119 static ctl_table powersave_nap_ctl_table[]={
 120         {
 121                 .procname       = "powersave-nap",
 122                 .data           = &powersave_nap,
 123                 .maxlen         = sizeof(int),
 124                 .mode           = 0644,
 125                 .proc_handler   = proc_dointvec,
 126         },
 127         {}
 128 };
 129 static ctl_table powersave_nap_sysctl_root[] = {
 130         {
 131                 .procname       = "kernel",
 132                 .mode           = 0555,
 133                 .child          = powersave_nap_ctl_table,
 134         },
 135         {}
 136 };
 137
 138 static int __init
 139 register_powersave_nap_sysctl(void)
 140 {
 141         register_sysctl_table(powersave_nap_sysctl_root);
 142
 143         return 0;
 144 }
 145 __initcall(register_powersave_nap_sysctl);
 146 #endif