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
  28 #include <asm/system.h>
  29 #include <asm/processor.h>
  30 #include <asm/cputable.h>
  31 #include <asm/time.h>
  32 #include <asm/machdep.h>
  33 #include <asm/smp.h>
  34
  35 #ifdef CONFIG_HOTPLUG_CPU
  36 /* this is used for software suspend, and that shuts down
  37  * CPUs even while the system is still booting... */
  38 #define cpu_should_die()        (cpu_is_offline(smp_processor_id()) && \
  39                                    (system_state == SYSTEM_RUNNING     \
  40                                  || system_state == SYSTEM_BOOTING))
  41 #else
  42 #define cpu_should_die()        0
  43 #endif
  44
  45 static int __init powersave_off(char *arg)
  46 {
  47         ppc_md.power_save = NULL;
  48         return 0;
  49 }
  50 __setup("powersave=off", powersave_off);
  51
  52 /*
  53  * The body of the idle task.
  54  */
  55 void cpu_idle(void)
  56 {
  57         if (ppc_md.idle_loop)
  58                 ppc_md.idle_loop();     /* doesn't return */
  59
  60         set_thread_flag(TIF_POLLING_NRFLAG);
  61         while (1) {
  62                 while (!need_resched() && !cpu_should_die()) {
  63                         ppc64_runlatch_off();
  64
  65                         if (ppc_md.power_save) {
  66                                 clear_thread_flag(TIF_POLLING_NRFLAG);
  67                                 /*
  68                                  * smp_mb is so clearing of TIF_POLLING_NRFLAG
  69                                  * is ordered w.r.t. need_resched() test.
  70                                  */
  71                                 smp_mb();
  72                                 local_irq_disable();
  73
  74                                 /* check again after disabling irqs */
  75                                 if (!need_resched() && !cpu_should_die())
  76                                         ppc_md.power_save();
  77
  78                                 local_irq_enable();
  79                                 set_thread_flag(TIF_POLLING_NRFLAG);
  80
  81                         } else {
  82                                 /*
  83                                  * Go into low thread priority and possibly
  84                                  * low power mode.
  85                                  */
  86                                 HMT_low();
  87                                 HMT_very_low();
  88                         }
  89                 }
  90
  91                 HMT_medium();
  92                 ppc64_runlatch_on();
  93                 if (cpu_should_die())
  94                         cpu_die();
  95                 preempt_enable_no_resched();
  96                 schedule();
  97                 preempt_disable();
  98         }
  99 }
 100
 101 int powersave_nap;
 102
 103 #ifdef CONFIG_SYSCTL
 104 /*
 105  * Register the sysctl to set/clear powersave_nap.
 106  */
 107 static ctl_table powersave_nap_ctl_table[]={
 108         {
 109                 .ctl_name       = KERN_PPC_POWERSAVE_NAP,
 110                 .procname       = "powersave-nap",
 111                 .data           = &powersave_nap,
 112                 .maxlen         = sizeof(int),
 113                 .mode           = 0644,
 114                 .proc_handler   = &proc_dointvec,
 115         },
 116         {}
 117 };
 118 static ctl_table powersave_nap_sysctl_root[] = {
 119         {
 120                 .ctl_name       = CTL_KERN,
 121                 .procname       = "kernel",
 122                 .mode           = 0755,
 123                 .child          = powersave_nap_ctl_table,
 124         },
 125         {}
 126 };
 127
 128 static int __init
 129 register_powersave_nap_sysctl(void)
 130 {
 131         register_sysctl_table(powersave_nap_sysctl_root);
 132
 133         return 0;
 134 }
 135 __initcall(register_powersave_nap_sysctl);
 136 #endif