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
  16 #include <asm/compiler.h>
  17
  18 extern unsigned long loops_per_jiffy;
  19
  20 static inline void __delay(unsigned long loops)
  21 {
  22         if (sizeof(long) == 4)
  23                 __asm__ __volatile__ (
  24                 ".set\tnoreorder\n"
  25                 "1:\tbnez\t%0,1b\n\t"
  26                 "subu\t%0,1\n\t"
  27                 ".set\treorder"
  28                 : "=r" (loops)
  29                 : "0" (loops));
  30         else if (sizeof(long) == 8)
  31                 __asm__ __volatile__ (
  32                 ".set\tnoreorder\n"
  33                 "1:\tbnez\t%0,1b\n\t"
  34                 "dsubu\t%0,1\n\t"
  35                 ".set\treorder"
  36                 :"=r" (loops)
  37                 :"0" (loops));
  38 }
  39
  40
  41 /*
  42  * Division by multiplication: you don't have to worry about
  43  * loss of precision.
  44  *
  45  * Use only for very small delays ( < 1 msec).  Should probably use a
  46  * lookup table, really, as the multiplications take much too long with
  47  * short delays.  This is a "reasonable" implementation, though (and the
  48  * first constant multiplications gets optimized away if the delay is
  49  * a constant)
  50  */
  51
  52 static inline void __udelay(unsigned long usecs, unsigned long lpj)
  53 {
  54         unsigned long lo;
  55
  56         /*
  57          * The common rates of 1000 and 128 are rounded wrongly by the
  58          * catchall case for 64-bit.  Excessive precission?  Probably ...
  59          */
  60 #if defined(CONFIG_MIPS64) && (HZ == 128)
  61         usecs *= 0x0008637bd05af6c7UL;          /* 2**64 / (1000000 / HZ) */
  62 #elif defined(CONFIG_MIPS64) && (HZ == 1000)
  63         usecs *= 0x004189374BC6A7f0UL;          /* 2**64 / (1000000 / HZ) */
  64 #elif defined(CONFIG_MIPS64)
  65         usecs *= (0x8000000000000000UL / (500000 / HZ));
  66 #else /* 32-bit junk follows here */
  67         usecs *= (unsigned long) (((0x8000000000000000ULL / (500000 / HZ)) +
  68                                    0x80000000ULL) >> 32);
  69 #endif
  70
  71         if (sizeof(long) == 4)
  72                 __asm__("multu\t%2, %3"
  73                 : "=h" (usecs), "=l" (lo)
  74                 : "r" (usecs), "r" (lpj)
  75                 : GCC_REG_ACCUM);
  76         else if (sizeof(long) == 8)
  77                 __asm__("dmultu\t%2, %3"
  78                 : "=h" (usecs), "=l" (lo)
  79                 : "r" (usecs), "r" (lpj)
  80                 : GCC_REG_ACCUM);
  81
  82         __delay(usecs);
  83 }
  84
  85 #ifdef CONFIG_SMP
  86 #define __udelay_val cpu_data[smp_processor_id()].udelay_val
  87 #else
  88 #define __udelay_val loops_per_jiffy
  89 #endif
  90
  91 #define udelay(usecs) __udelay((usecs),__udelay_val)
  92
  93 #endif /* _ASM_DELAY_H */