LXR linux/arch/arm64/lib/delay.c

   1/*
   2 * Delay loops based on the OpenRISC implementation.
   3 *
   4 * Copyright (C) 2012 ARM Limited
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful,
  11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 * GNU General Public License for more details.
  14 *
  15 * You should have received a copy of the GNU General Public License
  16 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 *
  18 * Author: Will Deacon <will.deacon@arm.com>
  19 */
  20
  21#include <linux/delay.h>
  22#include <linux/init.h>
  23#include <linux/kernel.h>
  24#include <linux/module.h>
  25#include <linux/timex.h>
  26
  27#include <clocksource/arm_arch_timer.h>
  28
  29#define USECS_TO_CYCLES(time_usecs)                     \
  30        xloops_to_cycles((time_usecs) * 0x10C7UL)
  31
  32static inline unsigned long xloops_to_cycles(unsigned long xloops)
  33{
  34        return (xloops * loops_per_jiffy * HZ) >> 32;
  35}
  36
  37void __delay(unsigned long cycles)
  38{
  39        cycles_t start = get_cycles();
  40
  41        if (arch_timer_evtstrm_available()) {
  42                const cycles_t timer_evt_period =
  43                        USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);
  44
  45                while ((get_cycles() - start + timer_evt_period) < cycles)
  46                        wfe();
  47        }
  48
  49        while ((get_cycles() - start) < cycles)
  50                cpu_relax();
  51}
  52EXPORT_SYMBOL(__delay);
  53
  54inline void __const_udelay(unsigned long xloops)
  55{
  56        __delay(xloops_to_cycles(xloops));
  57}
  58EXPORT_SYMBOL(__const_udelay);
  59
  60void __udelay(unsigned long usecs)
  61{
  62        __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
  63}
  64EXPORT_SYMBOL(__udelay);
  65
  66void __ndelay(unsigned long nsecs)
  67{
  68        __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
  69}
  70EXPORT_SYMBOL(__ndelay);
  71