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  */
  31 struct 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
  38 static 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
  46 static 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
  53 static void __timer_udelay(unsigned long usecs)
  54 {
  55         __timer_const_udelay(usecs * UDELAY_MULT);
  56 }
  57
  58 void __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
  68 unsigned long __cpuinit calibrate_delay_is_known(void)
  69 {
  70         return lpj_fine;
  71 }
  72 #endif