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