linux/arch/powerpc/include/asm/delay.h
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   1/* SPDX-License-Identifier: GPL-2.0-or-later */
   2#ifndef _ASM_POWERPC_DELAY_H
   3#define _ASM_POWERPC_DELAY_H
   4#ifdef __KERNEL__
   5
   6#include <linux/processor.h>
   7#include <asm/time.h>
   8
   9/*
  10 * Copyright 1996, Paul Mackerras.
  11 * Copyright (C) 2009 Freescale Semiconductor, Inc. All rights reserved.
  12 *
  13 * PPC64 Support added by Dave Engebretsen, Todd Inglett, Mike Corrigan,
  14 * Anton Blanchard.
  15 */
  16
  17extern void __delay(unsigned long loops);
  18extern void udelay(unsigned long usecs);
  19
  20/*
  21 * On shared processor machines the generic implementation of mdelay can
  22 * result in large errors. While each iteration of the loop inside mdelay
  23 * is supposed to take 1ms, the hypervisor could sleep our partition for
  24 * longer (eg 10ms). With the right timing these errors can add up.
  25 *
  26 * Since there is no 32bit overflow issue on 64bit kernels, just call
  27 * udelay directly.
  28 */
  29#ifdef CONFIG_PPC64
  30#define mdelay(n)       udelay((n) * 1000)
  31#endif
  32
  33/**
  34 * spin_event_timeout - spin until a condition gets true or a timeout elapses
  35 * @condition: a C expression to evalate
  36 * @timeout: timeout, in microseconds
  37 * @delay: the number of microseconds to delay between each evaluation of
  38 *         @condition
  39 *
  40 * The process spins until the condition evaluates to true (non-zero) or the
  41 * timeout elapses.  The return value of this macro is the value of
  42 * @condition when the loop terminates. This allows you to determine the cause
  43 * of the loop terminates.  If the return value is zero, then you know a
  44 * timeout has occurred.
  45 *
  46 * This primary purpose of this macro is to poll on a hardware register
  47 * until a status bit changes.  The timeout ensures that the loop still
  48 * terminates even if the bit never changes.  The delay is for devices that
  49 * need a delay in between successive reads.
  50 *
  51 * gcc will optimize out the if-statement if @delay is a constant.
  52 */
  53#define spin_event_timeout(condition, timeout, delay)                          \
  54({                                                                             \
  55        typeof(condition) __ret;                                               \
  56        unsigned long __loops = tb_ticks_per_usec * timeout;                   \
  57        unsigned long __start = get_tbl();                                     \
  58                                                                               \
  59        if (delay) {                                                           \
  60                while (!(__ret = (condition)) &&                               \
  61                                (tb_ticks_since(__start) <= __loops))          \
  62                        udelay(delay);                                         \
  63        } else {                                                               \
  64                spin_begin();                                                  \
  65                while (!(__ret = (condition)) &&                               \
  66                                (tb_ticks_since(__start) <= __loops))          \
  67                        spin_cpu_relax();                                      \
  68                spin_end();                                                    \
  69        }                                                                      \
  70        if (!__ret)                                                            \
  71                __ret = (condition);                                           \
  72        __ret;                                                                 \
  73})
  74
  75#endif /* __KERNEL__ */
  76#endif /* _ASM_POWERPC_DELAY_H */
  77