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
  23 extern 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
  48 static inline void ndelay(unsigned long x)
  49 {
  50         udelay(DIV_ROUND_UP(x, 1000));
  51 }
  52 #define ndelay(x) ndelay(x)
  53 #endif
  54
  55 extern unsigned long lpj_fine;
  56 void calibrate_delay(void);
  57 void msleep(unsigned int msecs);
  58 unsigned long msleep_interruptible(unsigned int msecs);
  59 void usleep_range(unsigned long min, unsigned long max);
  60
  61 static inline void ssleep(unsigned int seconds)
  62 {
  63         msleep(seconds * 1000);
  64 }
  65
  66 #endif /* defined(_LINUX_DELAY_H) */