arch/openrisc/lib/delay.c

   1 /*
   2  * OpenRISC Linux
   3  *
   4  * Linux architectural port borrowing liberally from similar works of
   5  * others.  All original copyrights apply as per the original source
   6  * declaration.
   7  *
   8  * Modifications for the OpenRISC architecture:
   9  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  10  *
  11  *      This program is free software; you can redistribute it and/or
  12  *      modify it under the terms of the GNU General Public License
  13  *      version 2 as published by the Free Software Foundation
  14  *
  15  * Precise Delay Loops
  16  */
  17
  18 #include <linux/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <asm/delay.h>
  22 #include <asm/timex.h>
  23 #include <asm/processor.h>
  24
  25 int __devinit read_current_timer(unsigned long *timer_value)
  26 {
  27         *timer_value = mfspr(SPR_TTCR);
  28         return 0;
  29 }
  30
  31 void __delay(unsigned long cycles)
  32 {
  33         cycles_t target = get_cycles() + cycles;
  34
  35         while (get_cycles() < target)
  36                 cpu_relax();
  37 }
  38 EXPORT_SYMBOL(__delay);
  39
  40 inline void __const_udelay(unsigned long xloops)
  41 {
  42         unsigned long long loops;
  43
  44         loops = xloops * loops_per_jiffy * HZ;
  45
  46         __delay(loops >> 32);
  47 }
  48 EXPORT_SYMBOL(__const_udelay);
  49
  50 void __udelay(unsigned long usecs)
  51 {
  52         __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
  53 }
  54 EXPORT_SYMBOL(__udelay);
  55
  56 void __ndelay(unsigned long nsecs)
  57 {
  58         __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
  59 }
  60 EXPORT_SYMBOL(__ndelay);