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
  32 extern void power4_idle(void);
  33
  34 void default_idle(void)
  35 {
  36         long oldval;
  37         unsigned int cpu = smp_processor_id();
  38
  39         while (1) {
  40                 oldval = test_and_clear_thread_flag(TIF_NEED_RESCHED);
  41
  42                 if (!oldval) {
  43                         set_thread_flag(TIF_POLLING_NRFLAG);
  44
  45                         while (!need_resched() && !cpu_is_offline(cpu)) {
  46                                 ppc64_runlatch_off();
  47
  48                                 /*
  49                                  * Go into low thread priority and possibly
  50                                  * low power mode.
  51                                  */
  52                                 HMT_low();
  53                                 HMT_very_low();
  54                         }
  55
  56                         HMT_medium();
  57                         clear_thread_flag(TIF_POLLING_NRFLAG);
  58                 } else {
  59                         set_need_resched();
  60                 }
  61
  62                 ppc64_runlatch_on();
  63                 schedule();
  64                 if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
  65                         cpu_die();
  66         }
  67 }
  68
  69 void native_idle(void)
  70 {
  71         while (1) {
  72                 ppc64_runlatch_off();
  73
  74                 if (!need_resched())
  75                         power4_idle();
  76
  77                 if (need_resched()) {
  78                         ppc64_runlatch_on();
  79                         schedule();
  80                 }
  81
  82                 if (cpu_is_offline(smp_processor_id()) &&
  83                     system_state == SYSTEM_RUNNING)
  84                         cpu_die();
  85         }
  86 }
  87
  88 void cpu_idle(void)
  89 {
  90         BUG_ON(NULL == ppc_md.idle_loop);
  91         ppc_md.idle_loop();
  92 }
  93
  94 int powersave_nap;
  95
  96 #ifdef CONFIG_SYSCTL
  97 /*
  98  * Register the sysctl to set/clear powersave_nap.
  99  */
 100 static ctl_table powersave_nap_ctl_table[]={
 101         {
 102                 .ctl_name       = KERN_PPC_POWERSAVE_NAP,
 103                 .procname       = "powersave-nap",
 104                 .data           = &powersave_nap,
 105                 .maxlen         = sizeof(int),
 106                 .mode           = 0644,
 107                 .proc_handler   = &proc_dointvec,
 108         },
 109         { 0, },
 110 };
 111 static ctl_table powersave_nap_sysctl_root[] = {
 112         { 1, "kernel", NULL, 0, 0755, powersave_nap_ctl_table, },
 113         { 0,},
 114 };
 115
 116 static int __init
 117 register_powersave_nap_sysctl(void)
 118 {
 119         register_sysctl_table(powersave_nap_sysctl_root, 0);
 120
 121         return 0;
 122 }
 123 __initcall(register_powersave_nap_sysctl);
 124 #endif