include/asm-mips/delay.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994 by Waldorf Electronics
   7  * Copyright (C) 1995 - 2000, 01, 03 by Ralf Baechle
   8  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
   9  */
  10 #ifndef _ASM_DELAY_H
  11 #define _ASM_DELAY_H
  12
  13 #include <linux/param.h>
  14 #include <linux/smp.h>
  15 #include <asm/compiler.h>
  16
  17 static inline void __delay(unsigned long loops)
  18 {
  19         if (sizeof(long) == 4)
  20                 __asm__ __volatile__ (
  21                 "       .set    noreorder                               \n"
  22                 "       .align  3                                       \n"
  23                 "1:     bnez    %0, 1b                                  \n"
  24                 "       subu    %0, 1                                   \n"
  25                 "       .set    reorder                                 \n"
  26                 : "=r" (loops)
  27                 : "0" (loops));
  28         else if (sizeof(long) == 8)
  29                 __asm__ __volatile__ (
  30                 "       .set    noreorder                               \n"
  31                 "       .align  3                                       \n"
  32                 "1:     bnez    %0, 1b                                  \n"
  33                 "       dsubu   %0, 1                                   \n"
  34                 "       .set    reorder                                 \n"
  35                 : "=r" (loops)
  36                 : "0" (loops));
  37 }
  38
  39
  40 /*
  41  * Division by multiplication: you don't have to worry about
  42  * loss of precision.
  43  *
  44  * Use only for very small delays ( < 1 msec).  Should probably use a
  45  * lookup table, really, as the multiplications take much too long with
  46  * short delays.  This is a "reasonable" implementation, though (and the
  47  * first constant multiplications gets optimized away if the delay is
  48  * a constant)
  49  */
  50
  51 static inline void __udelay(unsigned long usecs, unsigned long lpj)
  52 {
  53         unsigned long lo;
  54
  55         /*
  56          * The rates of 128 is rounded wrongly by the catchall case
  57          * for 64-bit.  Excessive precission?  Probably ...
  58          */
  59 #if defined(CONFIG_64BIT) && (HZ == 128)
  60         usecs *= 0x0008637bd05af6c7UL;          /* 2**64 / (1000000 / HZ) */
  61 #elif defined(CONFIG_64BIT)
  62         usecs *= (0x8000000000000000UL / (500000 / HZ));
  63 #else /* 32-bit junk follows here */
  64         usecs *= (unsigned long) (((0x8000000000000000ULL / (500000 / HZ)) +
  65                                    0x80000000ULL) >> 32);
  66 #endif
  67
  68         if (sizeof(long) == 4)
  69                 __asm__("multu\t%2, %3"
  70                 : "=h" (usecs), "=l" (lo)
  71                 : "r" (usecs), "r" (lpj)
  72                 : GCC_REG_ACCUM);
  73         else if (sizeof(long) == 8)
  74                 __asm__("dmultu\t%2, %3"
  75                 : "=h" (usecs), "=l" (lo)
  76                 : "r" (usecs), "r" (lpj)
  77                 : GCC_REG_ACCUM);
  78
  79         __delay(usecs);
  80 }
  81
  82 #define __udelay_val cpu_data[smp_processor_id()].udelay_val
  83
  84 #define udelay(usecs) __udelay((usecs),__udelay_val)
  85
  86 /* make sure "usecs *= ..." in udelay do not overflow. */
  87 #if HZ >= 1000
  88 #define MAX_UDELAY_MS   1
  89 #elif HZ <= 200
  90 #define MAX_UDELAY_MS   5
  91 #else
  92 #define MAX_UDELAY_MS   (1000 / HZ)
  93 #endif
  94
  95 #endif /* _ASM_DELAY_H */