LXR linux/arch/arm/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, write to the Free Software
  17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  18 *
  19 * Author: Will Deacon <will.deacon@arm.com>
  20 */
  21
  22#include <linux/delay.h>
  23#include <linux/init.h>
  24#include <linux/kernel.h>
  25#include <linux/module.h>
  26#include <linux/timex.h>
  27
  28/*
  29 * Default to the loop-based delay implementation.
  30 */
  31struct arm_delay_ops arm_delay_ops = {
  32        .delay          = __loop_delay,
  33        .const_udelay   = __loop_const_udelay,
  34        .udelay         = __loop_udelay,
  35};
  36
  37#ifdef ARCH_HAS_READ_CURRENT_TIMER
  38static void __timer_delay(unsigned long cycles)
  39{
  40        cycles_t start = get_cycles();
  41
  42        while ((get_cycles() - start) < cycles)
  43                cpu_relax();
  44}
  45
  46static void __timer_const_udelay(unsigned long xloops)
  47{
  48        unsigned long long loops = xloops;
  49        loops *= loops_per_jiffy;
  50        __timer_delay(loops >> UDELAY_SHIFT);
  51}
  52
  53static void __timer_udelay(unsigned long usecs)
  54{
  55        __timer_const_udelay(usecs * UDELAY_MULT);
  56}
  57
  58void __init init_current_timer_delay(unsigned long freq)
  59{
  60        pr_info("Switching to timer-based delay loop\n");
  61        lpj_fine                        = freq / HZ;
  62        loops_per_jiffy                 = lpj_fine;
  63        arm_delay_ops.delay             = __timer_delay;
  64        arm_delay_ops.const_udelay      = __timer_const_udelay;
  65        arm_delay_ops.udelay            = __timer_udelay;
  66}
  67
  68unsigned long __cpuinit calibrate_delay_is_known(void)
  69{
  70        return lpj_fine;
  71}
  72#endif
  73