arch/powerpc/include/asm/delay.h

   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
  17 extern void __delay(unsigned long loops);
  18 extern 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 = mftb();                                     \
  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 */