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