arch/arm/common/time-acorn.c

   1 /*
   2  *  linux/arch/arm/common/time-acorn.c
   3  *
   4  *  Copyright (c) 1996-2000 Russell King.
   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  *  Changelog:
  11  *   24-Sep-1996        RMK     Created
  12  *   10-Oct-1996        RMK     Brought up to date with arch-sa110eval
  13  *   04-Dec-1997        RMK     Updated for new arch/arm/time.c
  14  *   13=Jun-2004        DS      Moved to arch/arm/common b/c shared w/CLPS7500
  15  */
  16 #include <linux/timex.h>
  17 #include <linux/init.h>
  18
  19 #include <asm/hardware.h>
  20 #include <asm/io.h>
  21 #include <asm/hardware/ioc.h>
  22
  23 #include <asm/mach/time.h>
  24
  25 static unsigned long ioctime_gettimeoffset(void)
  26 {
  27         unsigned int count1, count2, status;
  28         long offset;
  29
  30         ioc_writeb (0, IOC_T0LATCH);
  31         barrier ();
  32         count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  33         barrier ();
  34         status = ioc_readb(IOC_IRQREQA);
  35         barrier ();
  36         ioc_writeb (0, IOC_T0LATCH);
  37         barrier ();
  38         count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  39
  40         offset = count2;
  41         if (count2 < count1) {
  42                 /*
  43                  * We have not had an interrupt between reading count1
  44                  * and count2.
  45                  */
  46                 if (status & (1 << 5))
  47                         offset -= LATCH;
  48         } else if (count2 > count1) {
  49                 /*
  50                  * We have just had another interrupt between reading
  51                  * count1 and count2.
  52                  */
  53                 offset -= LATCH;
  54         }
  55
  56         offset = (LATCH - offset) * (tick_nsec / 1000);
  57         return (offset + LATCH/2) / LATCH;
  58 }
  59
  60 void __init ioctime_init(void)
  61 {
  62         ioc_writeb(LATCH & 255, IOC_T0LTCHL);
  63         ioc_writeb(LATCH >> 8, IOC_T0LTCHH);
  64         ioc_writeb(0, IOC_T0GO);
  65
  66         gettimeoffset = ioctime_gettimeoffset;
  67 }