arch/mips/lib/delay.c

   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  * Copyright (C) 2007  Maciej W. Rozycki
  10  */
  11 #include <linux/module.h>
  12 #include <linux/param.h>
  13 #include <linux/smp.h>
  14
  15 #include <asm/compiler.h>
  16 #include <asm/war.h>
  17
  18 inline void __delay(unsigned int loops)
  19 {
  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 }
  29 EXPORT_SYMBOL(__delay);
  30
  31 /*
  32  * Division by multiplication: you don't have to worry about
  33  * loss of precision.
  34  *
  35  * Use only for very small delays ( < 1 msec).  Should probably use a
  36  * lookup table, really, as the multiplications take much too long with
  37  * short delays.  This is a "reasonable" implementation, though (and the
  38  * first constant multiplications gets optimized away if the delay is
  39  * a constant)
  40  */
  41
  42 void __udelay(unsigned long us)
  43 {
  44         unsigned int lpj = current_cpu_data.udelay_val;
  45
  46         __delay((us * 0x000010c7 * HZ * lpj) >> 32);
  47 }
  48 EXPORT_SYMBOL(__udelay);
  49
  50 void __ndelay(unsigned long ns)
  51 {
  52         unsigned int lpj = current_cpu_data.udelay_val;
  53
  54         __delay((us * 0x00000005 * HZ * lpj) >> 32);
  55 }
  56 EXPORT_SYMBOL(__ndelay);