LXR linux/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, 2014 Maciej W. Rozycki
  10 */
  11#include <linux/module.h>
  12#include <linux/param.h>
  13#include <linux/smp.h>
  14#include <linux/stringify.h>
  15
  16#include <asm/asm.h>
  17#include <asm/compiler.h>
  18#include <asm/war.h>
  19
  20#ifndef CONFIG_CPU_DADDI_WORKAROUNDS
  21#define GCC_DADDI_IMM_ASM() "I"
  22#else
  23#define GCC_DADDI_IMM_ASM() "r"
  24#endif
  25
  26void __delay(unsigned long loops)
  27{
  28        __asm__ __volatile__ (
  29        "       .set    noreorder                               \n"
  30        "       .align  3                                       \n"
  31        "1:     bnez    %0, 1b                                  \n"
  32        "        " __stringify(LONG_SUBU) "     %0, %1          \n"
  33        "       .set    reorder                                 \n"
  34        : "=r" (loops)
  35        : GCC_DADDI_IMM_ASM() (1), "0" (loops));
  36}
  37EXPORT_SYMBOL(__delay);
  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
  50void __udelay(unsigned long us)
  51{
  52        unsigned int lpj = raw_current_cpu_data.udelay_val;
  53
  54        __delay((us * 0x000010c7ull * HZ * lpj) >> 32);
  55}
  56EXPORT_SYMBOL(__udelay);
  57
  58void __ndelay(unsigned long ns)
  59{
  60        unsigned int lpj = raw_current_cpu_data.udelay_val;
  61
  62        __delay((ns * 0x00000005ull * HZ * lpj) >> 32);
  63}
  64EXPORT_SYMBOL(__ndelay);
  65