Line data    Source code

       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/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 __attribute__((weak)) calibration_delay_done(void);
      59             : void msleep(unsigned int msecs);
      60             : unsigned long msleep_interruptible(unsigned int msecs);
      61             : void usleep_range(unsigned long min, unsigned long max);
      62             : 
      63           0 : static inline void ssleep(unsigned int seconds)
      64             : {
      65           0 :         msleep(seconds * 1000);
      66           0 : }
      67             : 
      68             : /* see Documentation/timers/timers-howto.rst for the thresholds */
      69             : static inline void fsleep(unsigned long usecs)
      70             : {
      71             :         if (usecs <= 10)
      72             :                 udelay(usecs);
      73             :         else if (usecs <= 20000)
      74             :                 usleep_range(usecs, 2 * usecs);
      75             :         else
      76             :                 msleep(DIV_ROUND_UP(usecs, 1000));
      77             : }
      78             : 
      79             : #endif /* defined(_LINUX_DELAY_H) */