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
  32 static inline unsigned long xloops_to_cycles(unsigned long xloops)
  33 {
  34         return (xloops * loops_per_jiffy * HZ) >> 32;
  35 }
  36
  37 void __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 }
  52 EXPORT_SYMBOL(__delay);
  53
  54 inline void __const_udelay(unsigned long xloops)
  55 {
  56         __delay(xloops_to_cycles(xloops));
  57 }
  58 EXPORT_SYMBOL(__const_udelay);
  59
  60 void __udelay(unsigned long usecs)
  61 {
  62         __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
  63 }
  64 EXPORT_SYMBOL(__udelay);
  65
  66 void __ndelay(unsigned long nsecs)
  67 {
  68         __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
  69 }
  70 EXPORT_SYMBOL(__ndelay);