arch/ppc64/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  *
   7  * iSeries supported added by Mike Corrigan <mikejc@us.ibm.com>
   8  *
   9  * Additional shared processor, SMT, and firmware support
  10  *    Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com>
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version
  15  * 2 of the License, or (at your option) any later version.
  16  */
  17
  18 #include <linux/config.h>
  19 #include <linux/sched.h>
  20 #include <linux/kernel.h>
  21 #include <linux/smp.h>
  22 #include <linux/cpu.h>
  23 #include <linux/sysctl.h>
  24
  25 #include <asm/system.h>
  26 #include <asm/processor.h>
  27 #include <asm/cputable.h>
  28 #include <asm/time.h>
  29 #include <asm/systemcfg.h>
  30 #include <asm/machdep.h>
  31 #include <asm/smp.h>
  32
  33 extern void power4_idle(void);
  34
  35 void default_idle(void)
  36 {
  37         long oldval;
  38         unsigned int cpu = smp_processor_id();
  39
  40         while (1) {
  41                 oldval = test_and_clear_thread_flag(TIF_NEED_RESCHED);
  42
  43                 if (!oldval) {
  44                         set_thread_flag(TIF_POLLING_NRFLAG);
  45
  46                         while (!need_resched() && !cpu_is_offline(cpu)) {
  47                                 ppc64_runlatch_off();
  48
  49                                 /*
  50                                  * Go into low thread priority and possibly
  51                                  * low power mode.
  52                                  */
  53                                 HMT_low();
  54                                 HMT_very_low();
  55                         }
  56
  57                         HMT_medium();
  58                         clear_thread_flag(TIF_POLLING_NRFLAG);
  59                 } else {
  60                         set_need_resched();
  61                 }
  62
  63                 ppc64_runlatch_on();
  64                 schedule();
  65                 if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
  66                         cpu_die();
  67         }
  68 }
  69
  70 void native_idle(void)
  71 {
  72         while (1) {
  73                 ppc64_runlatch_off();
  74
  75                 if (!need_resched())
  76                         power4_idle();
  77
  78                 if (need_resched()) {
  79                         ppc64_runlatch_on();
  80                         schedule();
  81                 }
  82
  83                 if (cpu_is_offline(smp_processor_id()) &&
  84                     system_state == SYSTEM_RUNNING)
  85                         cpu_die();
  86         }
  87 }
  88
  89 void cpu_idle(void)
  90 {
  91         BUG_ON(NULL == ppc_md.idle_loop);
  92         ppc_md.idle_loop();
  93 }
  94
  95 int powersave_nap;
  96
  97 #ifdef CONFIG_SYSCTL
  98 /*
  99  * Register the sysctl to set/clear powersave_nap.
 100  */
 101 static ctl_table powersave_nap_ctl_table[]={
 102         {
 103                 .ctl_name       = KERN_PPC_POWERSAVE_NAP,
 104                 .procname       = "powersave-nap",
 105                 .data           = &powersave_nap,
 106                 .maxlen         = sizeof(int),
 107                 .mode           = 0644,
 108                 .proc_handler   = &proc_dointvec,
 109         },
 110         { 0, },
 111 };
 112 static ctl_table powersave_nap_sysctl_root[] = {
 113         { 1, "kernel", NULL, 0, 0755, powersave_nap_ctl_table, },
 114         { 0,},
 115 };
 116
 117 static int __init
 118 register_powersave_nap_sysctl(void)
 119 {
 120         register_sysctl_table(powersave_nap_sysctl_root, 0);
 121
 122         return 0;
 123 }
 124 __initcall(register_powersave_nap_sysctl);
 125 #endif