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 int 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         return 0;
  69 }
  70
  71 int native_idle(void)
  72 {
  73         while (1) {
  74                 ppc64_runlatch_off();
  75
  76                 if (!need_resched())
  77                         power4_idle();
  78
  79                 if (need_resched()) {
  80                         ppc64_runlatch_on();
  81                         schedule();
  82                 }
  83
  84                 if (cpu_is_offline(smp_processor_id()) &&
  85                     system_state == SYSTEM_RUNNING)
  86                         cpu_die();
  87         }
  88
  89         return 0;
  90 }
  91
  92 void cpu_idle(void)
  93 {
  94         BUG_ON(NULL == ppc_md.idle_loop);
  95         ppc_md.idle_loop();
  96 }
  97
  98 int powersave_nap;
  99
 100 #ifdef CONFIG_SYSCTL
 101 /*
 102  * Register the sysctl to set/clear powersave_nap.
 103  */
 104 static ctl_table powersave_nap_ctl_table[]={
 105         {
 106                 .ctl_name       = KERN_PPC_POWERSAVE_NAP,
 107                 .procname       = "powersave-nap",
 108                 .data           = &powersave_nap,
 109                 .maxlen         = sizeof(int),
 110                 .mode           = 0644,
 111                 .proc_handler   = &proc_dointvec,
 112         },
 113         { 0, },
 114 };
 115 static ctl_table powersave_nap_sysctl_root[] = {
 116         { 1, "kernel", NULL, 0, 0755, powersave_nap_ctl_table, },
 117         { 0,},
 118 };
 119
 120 static int __init
 121 register_powersave_nap_sysctl(void)
 122 {
 123         register_sysctl_table(powersave_nap_sysctl_root, 0);
 124
 125         return 0;
 126 }
 127 __initcall(register_powersave_nap_sysctl);
 128 #endif