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  * Written by Cort Dougan (cort@cs.nmt.edu)
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  */
  12 #include <linux/config.h>
  13 #include <linux/errno.h>
  14 #include <linux/sched.h>
  15 #include <linux/kernel.h>
  16 #include <linux/mm.h>
  17 #include <linux/smp.h>
  18 #include <linux/smp_lock.h>
  19 #include <linux/stddef.h>
  20 #include <linux/unistd.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/slab.h>
  23
  24 #include <asm/pgtable.h>
  25 #include <asm/uaccess.h>
  26 #include <asm/system.h>
  27 #include <asm/io.h>
  28 #include <asm/processor.h>
  29 #include <asm/mmu.h>
  30 #include <asm/cache.h>
  31
  32 #include <asm/time.h>
  33 #include <asm/iSeries/LparData.h>
  34 #include <asm/iSeries/HvCall.h>
  35 #include <asm/iSeries/ItLpQueue.h>
  36
  37 #ifdef CONFIG_PPC_ISERIES
  38 static void yield_shared_processor(void)
  39 {
  40         struct paca_struct *lpaca = get_paca();
  41         unsigned long tb;
  42
  43         HvCall_setEnabledInterrupts( HvCall_MaskIPI |
  44                                      HvCall_MaskLpEvent |
  45                                      HvCall_MaskLpProd |
  46                                      HvCall_MaskTimeout );
  47
  48         if ( ! ItLpQueue_isLpIntPending( paca->lpQueuePtr ) ) {
  49           tb = get_tb();
  50           /* Compute future tb value when yield should expire */
  51           HvCall_yieldProcessor( HvCall_YieldTimed, tb+tb_ticks_per_jiffy );
  52
  53           /* The decrementer stops during the yield.  Force a fake decrementer
  54            * here and let the timer_interrupt code sort out the actual time.
  55            */
  56           lpaca->xLpPaca.xIntDword.xFields.xDecrInt = 1;
  57         }
  58
  59         process_iSeries_events();
  60 }
  61 #endif /* CONFIG_PPC_ISERIES */
  62
  63 int idled(void)
  64 {
  65         struct paca_struct *lpaca;
  66         long oldval;
  67 #ifdef CONFIG_PPC_ISERIES
  68         unsigned long CTRL;
  69 #endif
  70
  71         /* endless loop with no priority at all */
  72         current->nice = 20;
  73         current->counter = -100;
  74 #ifdef CONFIG_PPC_ISERIES
  75         /* ensure iSeries run light will be out when idle */
  76         current->thread.flags &= ~PPC_FLAG_RUN_LIGHT;
  77         CTRL = mfspr(CTRLF);
  78         CTRL &= ~RUNLATCH;
  79         mtspr(CTRLT, CTRL);
  80 #endif
  81         init_idle();
  82
  83         lpaca = get_paca();
  84
  85         for (;;) {
  86 #ifdef CONFIG_PPC_ISERIES
  87                 if ( lpaca->xLpPaca.xSharedProc ) {
  88                         if ( ItLpQueue_isLpIntPending( lpaca->lpQueuePtr ) )
  89                                 process_iSeries_events();
  90                         if ( !current->need_resched )
  91                                 yield_shared_processor();
  92                 }
  93                 else
  94 #endif
  95                 {
  96                         /* Avoid an IPI by setting need_resched */
  97                         oldval = xchg(&current->need_resched, -1);
  98                         if (!oldval) {
  99                                 while(current->need_resched == -1) {
 100 #ifdef CONFIG_PPC_ISERIES
 101                                         HMT_medium();
 102                                         if ( ItLpQueue_isLpIntPending( lpaca->lpQueuePtr ) )
 103                                                 process_iSeries_events();
 104 #endif
 105                                         HMT_low();
 106                                 }
 107                         }
 108                 }
 109                 HMT_medium();
 110                 if (current->need_resched) {
 111                         schedule();
 112                         check_pgt_cache();
 113                 }
 114         }
 115         return 0;
 116 }
 117
 118 /*
 119  * SMP entry into the idle task - calls the same thing as the
 120  * non-smp versions. -- Cort
 121  */
 122 int cpu_idle(void)
 123 {
 124         idled();
 125         return 0;
 126 }