include/linux/delay.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_DELAY_H
   3 #define _LINUX_DELAY_H
   4
   5 /*
   6  * Copyright (C) 1993 Linus Torvalds
   7  *
   8  * Delay routines, using a pre-computed "loops_per_jiffy" value.
   9  *
  10  * Please note that ndelay(), udelay() and mdelay() may return early for
  11  * several reasons:
  12  *  1. computed loops_per_jiffy too low (due to the time taken to
  13  *     execute the timer interrupt.)
  14  *  2. cache behaviour affecting the time it takes to execute the
  15  *     loop function.
  16  *  3. CPU clock rate changes.
  17  *
  18  * Please see this thread:
  19  *   http://lists.openwall.net/linux-kernel/2011/01/09/56
  20  */
  21
  22 #include <linux/kernel.h>
  23
  24 extern unsigned long loops_per_jiffy;
  25
  26 #include <asm/delay.h>
  27
  28 /*
  29  * Using udelay() for intervals greater than a few milliseconds can
  30  * risk overflow for high loops_per_jiffy (high bogomips) machines. The
  31  * mdelay() provides a wrapper to prevent this.  For delays greater
  32  * than MAX_UDELAY_MS milliseconds, the wrapper is used.  Architecture
  33  * specific values can be defined in asm-???/delay.h as an override.
  34  * The 2nd mdelay() definition ensures GCC will optimize away the
  35  * while loop for the common cases where n <= MAX_UDELAY_MS  --  Paul G.
  36  */
  37
  38 #ifndef MAX_UDELAY_MS
  39 #define MAX_UDELAY_MS   5
  40 #endif
  41
  42 #ifndef mdelay
  43 #define mdelay(n) (\
  44         (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
  45         ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
  46 #endif
  47
  48 #ifndef ndelay
  49 static inline void ndelay(unsigned long x)
  50 {
  51         udelay(DIV_ROUND_UP(x, 1000));
  52 }
  53 #define ndelay(x) ndelay(x)
  54 #endif
  55
  56 extern unsigned long lpj_fine;
  57 void calibrate_delay(void);
  58 void msleep(unsigned int msecs);
  59 unsigned long msleep_interruptible(unsigned int msecs);
  60 void usleep_range(unsigned long min, unsigned long max);
  61
  62 static inline void ssleep(unsigned int seconds)
  63 {
  64         msleep(seconds * 1000);
  65 }
  66
  67 #endif /* defined(_LINUX_DELAY_H) */