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

   1#ifndef _ASM_POWERPC_DELAY_H
   2#define _ASM_POWERPC_DELAY_H
   3#ifdef __KERNEL__
   4
   5#include <asm/time.h>
   6
   7/*
   8 * Copyright 1996, Paul Mackerras.
   9 * Copyright (C) 2009 Freescale Semiconductor, Inc. All rights reserved.
  10 *
  11 * This program is free software; you can redistribute it and/or
  12 * modify it under the terms of the GNU General Public License
  13 * as published by the Free Software Foundation; either version
  14 * 2 of the License, or (at your option) any later version.
  15 *
  16 * PPC64 Support added by Dave Engebretsen, Todd Inglett, Mike Corrigan,
  17 * Anton Blanchard.
  18 */
  19
  20extern void __delay(unsigned long loops);
  21extern void udelay(unsigned long usecs);
  22
  23/*
  24 * On shared processor machines the generic implementation of mdelay can
  25 * result in large errors. While each iteration of the loop inside mdelay
  26 * is supposed to take 1ms, the hypervisor could sleep our partition for
  27 * longer (eg 10ms). With the right timing these errors can add up.
  28 *
  29 * Since there is no 32bit overflow issue on 64bit kernels, just call
  30 * udelay directly.
  31 */
  32#ifdef CONFIG_PPC64
  33#define mdelay(n)       udelay((n) * 1000)
  34#endif
  35
  36/**
  37 * spin_event_timeout - spin until a condition gets true or a timeout elapses
  38 * @condition: a C expression to evalate
  39 * @timeout: timeout, in microseconds
  40 * @delay: the number of microseconds to delay between each evaluation of
  41 *         @condition
  42 *
  43 * The process spins until the condition evaluates to true (non-zero) or the
  44 * timeout elapses.  The return value of this macro is the value of
  45 * @condition when the loop terminates. This allows you to determine the cause
  46 * of the loop terminates.  If the return value is zero, then you know a
  47 * timeout has occurred.
  48 *
  49 * This primary purpose of this macro is to poll on a hardware register
  50 * until a status bit changes.  The timeout ensures that the loop still
  51 * terminates even if the bit never changes.  The delay is for devices that
  52 * need a delay in between successive reads.
  53 *
  54 * gcc will optimize out the if-statement if @delay is a constant.
  55 */
  56#define spin_event_timeout(condition, timeout, delay)                          \
  57({                                                                             \
  58        typeof(condition) __ret;                                               \
  59        unsigned long __loops = tb_ticks_per_usec * timeout;                   \
  60        unsigned long __start = get_tbl();                                     \
  61        while (!(__ret = (condition)) && (tb_ticks_since(__start) <= __loops)) \
  62                if (delay)                                                     \
  63                        udelay(delay);                                         \
  64                else                                                           \
  65                        cpu_relax();                                           \
  66        if (!__ret)                                                            \
  67                __ret = (condition);                                           \
  68        __ret;                                                                 \
  69})
  70
  71#endif /* __KERNEL__ */
  72#endif /* _ASM_POWERPC_DELAY_H */
  73