arch/arm/mach-ebsa110/include/mach/system.h

   1 /*
   2  *  arch/arm/mach-ebsa110/include/mach/system.h
   3  *
   4  *  Copyright (C) 1996-2000 Russell King.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #ifndef __ASM_ARCH_SYSTEM_H
  11 #define __ASM_ARCH_SYSTEM_H
  12
  13 /*
  14  * EBSA110 idling methodology:
  15  *
  16  * We can not execute the "wait for interrupt" instruction since that
  17  * will stop our MCLK signal (which provides the clock for the glue
  18  * logic, and therefore the timer interrupt).
  19  *
  20  * Instead, we spin, polling the IRQ_STAT register for the occurrence
  21  * of any interrupt with core clock down to the memory clock.
  22  */
  23 static inline void arch_idle(void)
  24 {
  25         const char *irq_stat = (char *)0xff000000;
  26
  27         /* disable clock switching */
  28         asm volatile ("mcr p15, 0, ip, c15, c2, 2" : : : "cc");
  29
  30         /* wait for an interrupt to occur */
  31         while (!*irq_stat);
  32
  33         /* enable clock switching */
  34         asm volatile ("mcr p15, 0, ip, c15, c1, 2" : : : "cc");
  35 }
  36
  37 #endif