LXR linux/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_jiffy" value.
   8 *
   9 * Please note that ndelay(), udelay() and mdelay() may return early for
  10 * several reasons:
  11 *  1. computed loops_per_jiffy too low (due to the time taken to
  12 *     execute the timer interrupt.)
  13 *  2. cache behaviour affecting the time it takes to execute the
  14 *     loop function.
  15 *  3. CPU clock rate changes.
  16 *
  17 * Please see this thread:
  18 *   http://lists.openwall.net/linux-kernel/2011/01/09/56
  19 */
  20
  21#include <linux/kernel.h>
  22
  23extern unsigned long loops_per_jiffy;
  24
  25#include <asm/delay.h>
  26
  27/*
  28 * Using udelay() for intervals greater than a few milliseconds can
  29 * risk overflow for high loops_per_jiffy (high bogomips) machines. The
  30 * mdelay() provides a wrapper to prevent this.  For delays greater
  31 * than MAX_UDELAY_MS milliseconds, the wrapper is used.  Architecture
  32 * specific values can be defined in asm-???/delay.h as an override.
  33 * The 2nd mdelay() definition ensures GCC will optimize away the 
  34 * while loop for the common cases where n <= MAX_UDELAY_MS  --  Paul G.
  35 */
  36
  37#ifndef MAX_UDELAY_MS
  38#define MAX_UDELAY_MS   5
  39#endif
  40
  41#ifndef mdelay
  42#define mdelay(n) (\
  43        (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
  44        ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
  45#endif
  46
  47#ifndef ndelay
  48static inline void ndelay(unsigned long x)
  49{
  50        udelay(DIV_ROUND_UP(x, 1000));
  51}
  52#define ndelay(x) ndelay(x)
  53#endif
  54
  55extern unsigned long lpj_fine;
  56void calibrate_delay(void);
  57void msleep(unsigned int msecs);
  58unsigned long msleep_interruptible(unsigned int msecs);
  59void usleep_range(unsigned long min, unsigned long max);
  60
  61static inline void ssleep(unsigned int seconds)
  62{
  63        msleep(seconds * 1000);
  64}
  65
  66#endif /* defined(_LINUX_DELAY_H) */
  67