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 #include <linux/interrupt.h>
  19 #include <linux/irq.h>
  20
  21 #include <asm/hardware.h>
  22 #include <asm/io.h>
  23 #include <asm/hardware/ioc.h>
  24
  25 #include <asm/mach/time.h>
  26
  27 unsigned long ioc_timer_gettimeoffset(void)
  28 {
  29         unsigned int count1, count2, status;
  30         long offset;
  31
  32         ioc_writeb (0, IOC_T0LATCH);
  33         barrier ();
  34         count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  35         barrier ();
  36         status = ioc_readb(IOC_IRQREQA);
  37         barrier ();
  38         ioc_writeb (0, IOC_T0LATCH);
  39         barrier ();
  40         count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  41
  42         offset = count2;
  43         if (count2 < count1) {
  44                 /*
  45                  * We have not had an interrupt between reading count1
  46                  * and count2.
  47                  */
  48                 if (status & (1 << 5))
  49                         offset -= LATCH;
  50         } else if (count2 > count1) {
  51                 /*
  52                  * We have just had another interrupt between reading
  53                  * count1 and count2.
  54                  */
  55                 offset -= LATCH;
  56         }
  57
  58         offset = (LATCH - offset) * (tick_nsec / 1000);
  59         return (offset + LATCH/2) / LATCH;
  60 }
  61
  62 void __init ioctime_init(void)
  63 {
  64         ioc_writeb(LATCH & 255, IOC_T0LTCHL);
  65         ioc_writeb(LATCH >> 8, IOC_T0LTCHH);
  66         ioc_writeb(0, IOC_T0GO);
  67 }
  68
  69 static irqreturn_t
  70 ioc_timer_interrupt(int irq, void *dev_id)
  71 {
  72         write_seqlock(&xtime_lock);
  73         timer_tick();
  74         write_sequnlock(&xtime_lock);
  75         return IRQ_HANDLED;
  76 }
  77
  78 static struct irqaction ioc_timer_irq = {
  79         .name           = "timer",
  80         .flags          = IRQF_DISABLED,
  81         .handler        = ioc_timer_interrupt
  82 };
  83
  84 /*
  85  * Set up timer interrupt.
  86  */
  87 static void __init ioc_timer_init(void)
  88 {
  89         ioctime_init();
  90         setup_irq(IRQ_TIMER, &ioc_timer_irq);
  91 }
  92
  93 struct sys_timer ioc_timer = {
  94         .init           = ioc_timer_init,
  95         .offset         = ioc_timer_gettimeoffset,
  96 };
  97