arch/arm64/lib/delay.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Delay loops based on the OpenRISC implementation.
   4  *
   5  * Copyright (C) 2012 ARM Limited
   6  *
   7  * Author: Will Deacon <will.deacon@arm.com>
   8  */
   9
  10 #include <linux/delay.h>
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/timex.h>
  15
  16 #include <clocksource/arm_arch_timer.h>
  17
  18 #define USECS_TO_CYCLES(time_usecs)                     \
  19         xloops_to_cycles((time_usecs) * 0x10C7UL)
  20
  21 static inline unsigned long xloops_to_cycles(unsigned long xloops)
  22 {
  23         return (xloops * loops_per_jiffy * HZ) >> 32;
  24 }
  25
  26 void __delay(unsigned long cycles)
  27 {
  28         cycles_t start = get_cycles();
  29
  30         if (arch_timer_evtstrm_available()) {
  31                 const cycles_t timer_evt_period =
  32                         USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);
  33
  34                 while ((get_cycles() - start + timer_evt_period) < cycles)
  35                         wfe();
  36         }
  37
  38         while ((get_cycles() - start) < cycles)
  39                 cpu_relax();
  40 }
  41 EXPORT_SYMBOL(__delay);
  42
  43 inline void __const_udelay(unsigned long xloops)
  44 {
  45         __delay(xloops_to_cycles(xloops));
  46 }
  47 EXPORT_SYMBOL(__const_udelay);
  48
  49 void __udelay(unsigned long usecs)
  50 {
  51         __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
  52 }
  53 EXPORT_SYMBOL(__udelay);
  54
  55 void __ndelay(unsigned long nsecs)
  56 {
  57         __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
  58 }
  59 EXPORT_SYMBOL(__ndelay);