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