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/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 #else
  39 #define cpu_should_die()        0
  40 #endif
  41
  42 static int __init powersave_off(char *arg)
  43 {
  44         ppc_md.power_save = NULL;
  45         return 0;
  46 }
  47 __setup("powersave=off", powersave_off);
  48
  49 /*
  50  * The body of the idle task.
  51  */
  52 void cpu_idle(void)
  53 {
  54         if (ppc_md.idle_loop)
  55                 ppc_md.idle_loop();     /* doesn't return */
  56
  57         set_thread_flag(TIF_POLLING_NRFLAG);
  58         while (1) {
  59                 tick_nohz_stop_sched_tick(1);
  60                 while (!need_resched() && !cpu_should_die()) {
  61                         ppc64_runlatch_off();
  62
  63                         if (ppc_md.power_save) {
  64                                 clear_thread_flag(TIF_POLLING_NRFLAG);
  65                                 /*
  66                                  * smp_mb is so clearing of TIF_POLLING_NRFLAG
  67                                  * is ordered w.r.t. need_resched() test.
  68                                  */
  69                                 smp_mb();
  70                                 local_irq_disable();
  71
  72                                 /* Don't trace irqs off for idle */
  73                                 stop_critical_timings();
  74
  75                                 /* check again after disabling irqs */
  76                                 if (!need_resched() && !cpu_should_die())
  77                                         ppc_md.power_save();
  78
  79                                 start_critical_timings();
  80
  81                                 local_irq_enable();
  82                                 set_thread_flag(TIF_POLLING_NRFLAG);
  83
  84                         } else {
  85                                 /*
  86                                  * Go into low thread priority and possibly
  87                                  * low power mode.
  88                                  */
  89                                 HMT_low();
  90                                 HMT_very_low();
  91                         }
  92                 }
  93
  94                 HMT_medium();
  95                 ppc64_runlatch_on();
  96                 tick_nohz_restart_sched_tick();
  97                 preempt_enable_no_resched();
  98                 if (cpu_should_die())
  99                         cpu_die();
 100                 schedule();
 101                 preempt_disable();
 102         }
 103 }
 104
 105 int powersave_nap;
 106
 107 #ifdef CONFIG_SYSCTL
 108 /*
 109  * Register the sysctl to set/clear powersave_nap.
 110  */
 111 static ctl_table powersave_nap_ctl_table[]={
 112         {
 113                 .procname       = "powersave-nap",
 114                 .data           = &powersave_nap,
 115                 .maxlen         = sizeof(int),
 116                 .mode           = 0644,
 117                 .proc_handler   = proc_dointvec,
 118         },
 119         {}
 120 };
 121 static ctl_table powersave_nap_sysctl_root[] = {
 122         {
 123                 .procname       = "kernel",
 124                 .mode           = 0555,
 125                 .child          = powersave_nap_ctl_table,
 126         },
 127         {}
 128 };
 129
 130 static int __init
 131 register_powersave_nap_sysctl(void)
 132 {
 133         register_sysctl_table(powersave_nap_sysctl_root);
 134
 135         return 0;
 136 }
 137 __initcall(register_powersave_nap_sysctl);
 138 #endif