include/asm-powerpc/delay.h

   1 #ifndef _ASM_POWERPC_DELAY_H
   2 #define _ASM_POWERPC_DELAY_H
   3
   4 /*
   5  * Copyright 1996, Paul Mackerras.
   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  * PPC64 Support added by Dave Engebretsen, Todd Inglett, Mike Corrigan,
  13  * Anton Blanchard.
  14  */
  15
  16 extern unsigned long tb_ticks_per_usec;
  17
  18 #ifdef CONFIG_PPC64
  19 /* define these here to prevent circular dependencies */
  20 /* these instructions control the thread priority on multi-threaded cpus */
  21 #define __HMT_low()     asm volatile("or 1,1,1")
  22 #define __HMT_medium()  asm volatile("or 2,2,2")
  23 #else
  24 #define __HMT_low()
  25 #define __HMT_medium()
  26 #endif
  27
  28 #define __barrier()     asm volatile("" ::: "memory")
  29
  30 static inline unsigned long __get_tb(void)
  31 {
  32         unsigned long rval;
  33
  34         asm volatile("mftb %0" : "=r" (rval));
  35         return rval;
  36 }
  37
  38 static inline void __delay(unsigned long loops)
  39 {
  40         unsigned long start = __get_tb();
  41
  42         while((__get_tb() - start) < loops)
  43                 __HMT_low();
  44         __HMT_medium();
  45         __barrier();
  46 }
  47
  48 static inline void udelay(unsigned long usecs)
  49 {
  50         unsigned long loops = tb_ticks_per_usec * usecs;
  51
  52         __delay(loops);
  53 }
  54
  55 #endif /* _ASM_POWERPC_DELAY_H */