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  *   https://lists.openwall.net/linux-kernel/2011/01/09/56
  20  */
  21
  22 #include <linux/math.h>
  23 #include <linux/sched.h>
  24
  25 extern unsigned long loops_per_jiffy;
  26
  27 #include <asm/delay.h>
  28
  29 /*
  30  * Using udelay() for intervals greater than a few milliseconds can
  31  * risk overflow for high loops_per_jiffy (high bogomips) machines. The
  32  * mdelay() provides a wrapper to prevent this.  For delays greater
  33  * than MAX_UDELAY_MS milliseconds, the wrapper is used.  Architecture
  34  * specific values can be defined in asm-???/delay.h as an override.
  35  * The 2nd mdelay() definition ensures GCC will optimize away the
  36  * while loop for the common cases where n <= MAX_UDELAY_MS  --  Paul G.
  37  */
  38
  39 #ifndef MAX_UDELAY_MS
  40 #define MAX_UDELAY_MS   5
  41 #endif
  42
  43 #ifndef mdelay
  44 #define mdelay(n) (\
  45         (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
  46         ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
  47 #endif
  48
  49 #ifndef ndelay
  50 static inline void ndelay(unsigned long x)
  51 {
  52         udelay(DIV_ROUND_UP(x, 1000));
  53 }
  54 #define ndelay(x) ndelay(x)
  55 #endif
  56
  57 extern unsigned long lpj_fine;
  58 void calibrate_delay(void);
  59 unsigned long calibrate_delay_is_known(void);
  60 void __attribute__((weak)) calibration_delay_done(void);
  61 void msleep(unsigned int msecs);
  62 unsigned long msleep_interruptible(unsigned int msecs);
  63 void usleep_range_state(unsigned long min, unsigned long max,
  64                         unsigned int state);
  65
  66 static inline void usleep_range(unsigned long min, unsigned long max)
  67 {
  68         usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
  69 }
  70
  71 static inline void usleep_idle_range(unsigned long min, unsigned long max)
  72 {
  73         usleep_range_state(min, max, TASK_IDLE);
  74 }
  75
  76 static inline void ssleep(unsigned int seconds)
  77 {
  78         msleep(seconds * 1000);
  79 }
  80
  81 /* see Documentation/timers/timers-howto.rst for the thresholds */
  82 static inline void fsleep(unsigned long usecs)
  83 {
  84         if (usecs <= 10)
  85                 udelay(usecs);
  86         else if (usecs <= 20000)
  87                 usleep_range(usecs, 2 * usecs);
  88         else
  89                 msleep(DIV_ROUND_UP(usecs, 1000));
  90 }
  91
  92 #endif /* defined(_LINUX_DELAY_H) */