include/linux/delay.h

   1 #ifndef _LINUX_DELAY_H
   2 #define _LINUX_DELAY_H
   3
   4 /*
   5  * Copyright (C) 1993 Linus Torvalds
   6  *
   7  * Delay routines, using a pre-computed "loops_per_second" value.
   8  */
   9
  10 extern unsigned long loops_per_sec;
  11
  12 #include <asm/delay.h>
  13
  14 /*
  15  * Using udelay() for intervals greater than a few milliseconds can
  16  * risk overflow for high loops_per_sec (high bogomips) machines. The
  17  * mdelay() provides a wrapper to prevent this.  For delays greater
  18  * than MAX_UDELAY_MS milliseconds, the wrapper is used.  Architecture
  19  * specific values can be defined in asm-???/delay.h as an override.
  20  * The 2nd mdelay() definition ensures GCC will optimize away the
  21  * while loop for the common cases where n <= MAX_UDELAY_MS  --  Paul G.
  22  */
  23
  24 #ifndef MAX_UDELAY_MS
  25 #define MAX_UDELAY_MS   5
  26 #endif
  27
  28 #ifdef notdef
  29 #define mdelay(n) (\
  30         {unsigned long msec=(n); while (msec--) udelay(1000);})
  31 #else
  32 #define mdelay(n) (\
  33         (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
  34         ({unsigned long msec=(n); while (msec--) udelay(1000);}))
  35 #endif
  36
  37 #endif /* defined(_LINUX_DELAY_H) */