arch/arm/include/asm/delay.h

   1 /*
   2  * Copyright (C) 1995-2004 Russell King
   3  *
   4  * Delay routines, using a pre-computed "loops_per_second" value.
   5  */
   6 #ifndef __ASM_ARM_DELAY_H
   7 #define __ASM_ARM_DELAY_H
   8
   9 #include <asm/memory.h>
  10 #include <asm/param.h>  /* HZ */
  11
  12 #define MAX_UDELAY_MS   2
  13 #define UDELAY_MULT     ((UL(2199023) * HZ) >> 11)
  14 #define UDELAY_SHIFT    30
  15
  16 #ifndef __ASSEMBLY__
  17
  18 struct delay_timer {
  19         unsigned long (*read_current_timer)(void);
  20         unsigned long freq;
  21 };
  22
  23 extern struct arm_delay_ops {
  24         void (*delay)(unsigned long);
  25         void (*const_udelay)(unsigned long);
  26         void (*udelay)(unsigned long);
  27         unsigned long ticks_per_jiffy;
  28 } arm_delay_ops;
  29
  30 #define __delay(n)              arm_delay_ops.delay(n)
  31
  32 /*
  33  * This function intentionally does not exist; if you see references to
  34  * it, it means that you're calling udelay() with an out of range value.
  35  *
  36  * With currently imposed limits, this means that we support a max delay
  37  * of 2000us. Further limits: HZ<=1000 and bogomips<=3355
  38  */
  39 extern void __bad_udelay(void);
  40
  41 /*
  42  * division by multiplication: you don't have to worry about
  43  * loss of precision.
  44  *
  45  * Use only for very small delays ( < 2 msec).  Should probably use a
  46  * lookup table, really, as the multiplications take much too long with
  47  * short delays.  This is a "reasonable" implementation, though (and the
  48  * first constant multiplications gets optimized away if the delay is
  49  * a constant)
  50  */
  51 #define __udelay(n)             arm_delay_ops.udelay(n)
  52 #define __const_udelay(n)       arm_delay_ops.const_udelay(n)
  53
  54 #define udelay(n)                                                       \
  55         (__builtin_constant_p(n) ?                                      \
  56           ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() :              \
  57                         __const_udelay((n) * UDELAY_MULT)) :            \
  58           __udelay(n))
  59
  60 /* Loop-based definitions for assembly code. */
  61 extern void __loop_delay(unsigned long loops);
  62 extern void __loop_udelay(unsigned long usecs);
  63 extern void __loop_const_udelay(unsigned long);
  64
  65 /* Delay-loop timer registration. */
  66 #define ARCH_HAS_READ_CURRENT_TIMER
  67 extern void register_current_timer_delay(const struct delay_timer *timer);
  68
  69 #endif /* __ASSEMBLY__ */
  70
  71 #endif /* defined(_ARM_DELAY_H) */
  72