arch/arm/mach-rpc/time.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 #include <linux/io.h>
  21
  22 #include <mach/hardware.h>
  23 #include <asm/hardware/ioc.h>
  24
  25 #include <asm/mach/time.h>
  26
  27 #define RPC_CLOCK_FREQ 2000000
  28 #define RPC_LATCH DIV_ROUND_CLOSEST(RPC_CLOCK_FREQ, HZ)
  29
  30 static u32 ioc_timer_gettimeoffset(void)
  31 {
  32         unsigned int count1, count2, status;
  33         long offset;
  34
  35         ioc_writeb (0, IOC_T0LATCH);
  36         barrier ();
  37         count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  38         barrier ();
  39         status = ioc_readb(IOC_IRQREQA);
  40         barrier ();
  41         ioc_writeb (0, IOC_T0LATCH);
  42         barrier ();
  43         count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  44
  45         offset = count2;
  46         if (count2 < count1) {
  47                 /*
  48                  * We have not had an interrupt between reading count1
  49                  * and count2.
  50                  */
  51                 if (status & (1 << 5))
  52                         offset -= RPC_LATCH;
  53         } else if (count2 > count1) {
  54                 /*
  55                  * We have just had another interrupt between reading
  56                  * count1 and count2.
  57                  */
  58                 offset -= RPC_LATCH;
  59         }
  60
  61         offset = (RPC_LATCH - offset) * (tick_nsec / 1000);
  62         return DIV_ROUND_CLOSEST(offset, RPC_LATCH) * 1000;
  63 }
  64
  65 void __init ioctime_init(void)
  66 {
  67         ioc_writeb(RPC_LATCH & 255, IOC_T0LTCHL);
  68         ioc_writeb(RPC_LATCH >> 8, IOC_T0LTCHH);
  69         ioc_writeb(0, IOC_T0GO);
  70 }
  71
  72 static irqreturn_t
  73 ioc_timer_interrupt(int irq, void *dev_id)
  74 {
  75         timer_tick();
  76         return IRQ_HANDLED;
  77 }
  78
  79 static struct irqaction ioc_timer_irq = {
  80         .name           = "timer",
  81         .handler        = ioc_timer_interrupt
  82 };
  83
  84 /*
  85  * Set up timer interrupt.
  86  */
  87 void __init ioc_timer_init(void)
  88 {
  89         arch_gettimeoffset = ioc_timer_gettimeoffset;
  90         ioctime_init();
  91         setup_irq(IRQ_TIMER0, &ioc_timer_irq);
  92 }