include/asm-m68knommu/delay.h

   1 #ifndef _M68KNOMMU_DELAY_H
   2 #define _M68KNOMMU_DELAY_H
   3
   4 /*
   5  * Copyright (C) 1994 Hamish Macdonald
   6  * Copyright (C) 2004 Greg Ungerer <gerg@snapgear.com>
   7  */
   8
   9 #include <asm/param.h>
  10
  11 static inline void __delay(unsigned long loops)
  12 {
  13 #if defined(CONFIG_COLDFIRE)
  14         /* The coldfire runs this loop at significantly different speeds
  15          * depending upon long word alignment or not.  We'll pad it to
  16          * long word alignment which is the faster version.
  17          * The 0x4a8e is of course a 'tstl %fp' instruction.  This is better
  18          * than using a NOP (0x4e71) instruction because it executes in one
  19          * cycle not three and doesn't allow for an arbitary delay waiting
  20          * for bus cycles to finish.  Also fp/a6 isn't likely to cause a
  21          * stall waiting for the register to become valid if such is added
  22          * to the coldfire at some stage.
  23          */
  24         __asm__ __volatile__ (  ".balignw 4, 0x4a8e\n\t"
  25                                 "1: subql #1, %0\n\t"
  26                                 "jcc 1b"
  27                 : "=d" (loops) : "0" (loops));
  28 #else
  29         __asm__ __volatile__ (  "1: subql #1, %0\n\t"
  30                                 "jcc 1b"
  31                 : "=d" (loops) : "0" (loops));
  32 #endif
  33 }
  34
  35 /*
  36  *      Ideally we use a 32*32->64 multiply to calculate the number of
  37  *      loop iterations, but the older standard 68k and ColdFire do not
  38  *      have this instruction. So for them we have a clsoe approximation
  39  *      loop using 32*32->32 multiplies only. This calculation based on
  40  *      the ARM version of delay.
  41  *
  42  *      We want to implement:
  43  *
  44  *      loops = (usecs * 0x10c6 * HZ * loops_per_jiffy) / 2^32
  45  */
  46
  47 #define HZSCALE         (268435456 / (1000000/HZ))
  48
  49 extern unsigned long loops_per_jiffy;
  50
  51 static inline void _udelay(unsigned long usecs)
  52 {
  53 #if defined(CONFIG_M68328) || defined(CONFIG_M68EZ328) || \
  54     defined(CONFIG_M68VZ328) || defined(CONFIG_M68360) || \
  55     defined(CONFIG_COLDFIRE)
  56         __delay((((usecs * HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6);
  57 #else
  58         unsigned long tmp;
  59
  60         usecs *= 4295;          /* 2**32 / 1000000 */
  61         __asm__ ("mulul %2,%0:%1"
  62                 : "=d" (usecs), "=d" (tmp)
  63                 : "d" (usecs), "1" (loops_per_jiffy*HZ));
  64         __delay(usecs);
  65 #endif
  66 }
  67
  68 /*
  69  *      Moved the udelay() function into library code, no longer inlined.
  70  *      I had to change the algorithm because we are overflowing now on
  71  *      the faster ColdFire parts. The code is a little biger, so it makes
  72  *      sense to library it.
  73  */
  74 extern void udelay(unsigned long usecs);
  75
  76 #endif /* defined(_M68KNOMMU_DELAY_H) */