arch/sh/kernel/idle.c

   1 /*
   2  * The idle loop for all SuperH platforms.
   3  *
   4  *  Copyright (C) 2002 - 2009  Paul Mundt
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  */
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/mm.h>
  13 #include <linux/pm.h>
  14 #include <linux/tick.h>
  15 #include <linux/preempt.h>
  16 #include <linux/thread_info.h>
  17 #include <linux/irqflags.h>
  18 #include <linux/smp.h>
  19 #include <asm/pgalloc.h>
  20 #include <asm/system.h>
  21 #include <asm/atomic.h>
  22
  23 static int hlt_counter;
  24 void (*pm_idle)(void);
  25 void (*pm_power_off)(void);
  26 EXPORT_SYMBOL(pm_power_off);
  27
  28 static int __init nohlt_setup(char *__unused)
  29 {
  30         hlt_counter = 1;
  31         return 1;
  32 }
  33 __setup("nohlt", nohlt_setup);
  34
  35 static int __init hlt_setup(char *__unused)
  36 {
  37         hlt_counter = 0;
  38         return 1;
  39 }
  40 __setup("hlt", hlt_setup);
  41
  42 void default_idle(void)
  43 {
  44         if (!hlt_counter) {
  45                 clear_thread_flag(TIF_POLLING_NRFLAG);
  46                 smp_mb__after_clear_bit();
  47                 set_bl_bit();
  48                 stop_critical_timings();
  49
  50                 while (!need_resched())
  51                         cpu_sleep();
  52
  53                 start_critical_timings();
  54                 clear_bl_bit();
  55                 set_thread_flag(TIF_POLLING_NRFLAG);
  56         } else
  57                 while (!need_resched())
  58                         cpu_relax();
  59 }
  60
  61 void cpu_idle(void)
  62 {
  63         set_thread_flag(TIF_POLLING_NRFLAG);
  64
  65         /* endless idle loop with no priority at all */
  66         while (1) {
  67                 void (*idle)(void) = pm_idle;
  68
  69                 if (!idle)
  70                         idle = default_idle;
  71
  72                 tick_nohz_stop_sched_tick(1);
  73                 while (!need_resched())
  74                         idle();
  75                 tick_nohz_restart_sched_tick();
  76
  77                 preempt_enable_no_resched();
  78                 schedule();
  79                 preempt_disable();
  80                 check_pgt_cache();
  81         }
  82 }
  83
  84 static void do_nothing(void *unused)
  85 {
  86 }
  87
  88 /*
  89  * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
  90  * pm_idle and update to new pm_idle value. Required while changing pm_idle
  91  * handler on SMP systems.
  92  *
  93  * Caller must have changed pm_idle to the new value before the call. Old
  94  * pm_idle value will not be used by any CPU after the return of this function.
  95  */
  96 void cpu_idle_wait(void)
  97 {
  98         smp_mb();
  99         /* kick all the CPUs so that they exit out of pm_idle */
 100         smp_call_function(do_nothing, NULL, 1);
 101 }
 102 EXPORT_SYMBOL_GPL(cpu_idle_wait);