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