LXR linux/arch/xtensa/include/asm/delay.h

   1/*
   2 * include/asm-xtensa/delay.h
   3 *
   4 * This file is subject to the terms and conditions of the GNU General Public
   5 * License.  See the file "COPYING" in the main directory of this archive
   6 * for more details.
   7 *
   8 * Copyright (C) 2001 - 2005 Tensilica Inc.
   9 *
  10 */
  11
  12#ifndef _XTENSA_DELAY_H
  13#define _XTENSA_DELAY_H
  14
  15#include <asm/timex.h>
  16#include <asm/param.h>
  17
  18extern unsigned long loops_per_jiffy;
  19
  20static inline void __delay(unsigned long loops)
  21{
  22        if (__builtin_constant_p(loops) && loops < 2)
  23                __asm__ __volatile__ ("nop");
  24        else if (loops >= 2)
  25                /* 2 cycles per loop. */
  26                __asm__ __volatile__ ("1: addi %0, %0, -2; bgeui %0, 2, 1b"
  27                                : "+r" (loops));
  28}
  29
  30/* Undefined function to get compile-time error */
  31void __bad_udelay(void);
  32void __bad_ndelay(void);
  33
  34#define __MAX_UDELAY 30000
  35#define __MAX_NDELAY 30000
  36
  37static inline void __udelay(unsigned long usecs)
  38{
  39        unsigned long start = get_ccount();
  40        unsigned long cycles = (usecs * (ccount_freq >> 15)) >> 5;
  41
  42        /* Note: all variables are unsigned (can wrap around)! */
  43        while (((unsigned long)get_ccount()) - start < cycles)
  44                cpu_relax();
  45}
  46
  47static inline void udelay(unsigned long usec)
  48{
  49        if (__builtin_constant_p(usec) && usec >= __MAX_UDELAY)
  50                __bad_udelay();
  51        else
  52                __udelay(usec);
  53}
  54
  55static inline void __ndelay(unsigned long nsec)
  56{
  57        /*
  58         * Inner shift makes sure multiplication doesn't overflow
  59         * for legitimate nsec values
  60         */
  61        unsigned long cycles = (nsec * (ccount_freq >> 15)) >> 15;
  62        __delay(cycles);
  63}
  64
  65#define ndelay(n) ndelay(n)
  66
  67static inline void ndelay(unsigned long nsec)
  68{
  69        if (__builtin_constant_p(nsec) && nsec >= __MAX_NDELAY)
  70                __bad_ndelay();
  71        else
  72                __ndelay(nsec);
  73}
  74
  75#endif
  76