arch/m68k/include/asm/delay.h

   1 #ifndef _M68K_DELAY_H
   2 #define _M68K_DELAY_H
   3
   4 #include <asm/param.h>
   5
   6 /*
   7  * Copyright (C) 1994 Hamish Macdonald
   8  * Copyright (C) 2004 Greg Ungerer <gerg@uclinux.com>
   9  *
  10  * Delay routines, using a pre-computed "loops_per_jiffy" value.
  11  */
  12
  13 #if defined(CONFIG_COLDFIRE)
  14 /*
  15  * The ColdFire runs the delay loop at significantly different speeds
  16  * depending upon long word alignment or not.  We'll pad it to
  17  * long word alignment which is the faster version.
  18  * The 0x4a8e is of course a 'tstl %fp' instruction.  This is better
  19  * than using a NOP (0x4e71) instruction because it executes in one
  20  * cycle not three and doesn't allow for an arbitrary delay waiting
  21  * for bus cycles to finish.  Also fp/a6 isn't likely to cause a
  22  * stall waiting for the register to become valid if such is added
  23  * to the coldfire at some stage.
  24  */
  25 #define DELAY_ALIGN     ".balignw 4, 0x4a8e\n\t"
  26 #else
  27 /*
  28  * No instruction alignment required for other m68k types.
  29  */
  30 #define DELAY_ALIGN
  31 #endif
  32
  33 static inline void __delay(unsigned long loops)
  34 {
  35         __asm__ __volatile__ (
  36                 DELAY_ALIGN
  37                 "1: subql #1,%0\n\t"
  38                 "jcc 1b"
  39                 : "=d" (loops)
  40                 : "0" (loops));
  41 }
  42
  43 extern void __bad_udelay(void);
  44
  45
  46 #if defined(CONFIG_M68000) || defined(CONFIG_COLDFIRE)
  47 /*
  48  * The simpler m68k and ColdFire processors do not have a 32*32->64
  49  * multiply instruction. So we need to handle them a little differently.
  50  * We use a bit of shifting and a single 32*32->32 multiply to get close.
  51  * This is a macro so that the const version can factor out the first
  52  * multiply and shift.
  53  */
  54 #define HZSCALE         (268435456 / (1000000 / HZ))
  55
  56 #define __const_udelay(u) \
  57         __delay(((((u) * HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6)
  58
  59 #else
  60
  61 static inline void __xdelay(unsigned long xloops)
  62 {
  63         unsigned long tmp;
  64
  65         __asm__ ("mulul %2,%0:%1"
  66                 : "=d" (xloops), "=d" (tmp)
  67                 : "d" (xloops), "1" (loops_per_jiffy));
  68         __delay(xloops * HZ);
  69 }
  70
  71 /*
  72  * The definition of __const_udelay is specifically made a macro so that
  73  * the const factor (4295 = 2**32 / 1000000) can be optimized out when
  74  * the delay is a const.
  75  */
  76 #define __const_udelay(n)       (__xdelay((n) * 4295))
  77
  78 #endif
  79
  80 static inline void __udelay(unsigned long usecs)
  81 {
  82         __const_udelay(usecs);
  83 }
  84
  85 /*
  86  * Use only for very small delays ( < 1 msec).  Should probably use a
  87  * lookup table, really, as the multiplications take much too long with
  88  * short delays.  This is a "reasonable" implementation, though (and the
  89  * first constant multiplications gets optimized away if the delay is
  90  * a constant)
  91  */
  92 #define udelay(n) (__builtin_constant_p(n) ? \
  93         ((n) > 20000 ? __bad_udelay() : __const_udelay(n)) : __udelay(n))
  94
  95
  96 #endif /* defined(_M68K_DELAY_H) */