Root/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#include <linux/io.h>
21
22#include <mach/hardware.h>
23#include <asm/hardware/ioc.h>
24
25#include <asm/mach/time.h>
26
27unsigned 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
62void __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
69static irqreturn_t
70ioc_timer_interrupt(int irq, void *dev_id)
71{
72    timer_tick();
73    return IRQ_HANDLED;
74}
75
76static struct irqaction ioc_timer_irq = {
77    .name = "timer",
78    .flags = IRQF_DISABLED,
79    .handler = ioc_timer_interrupt
80};
81
82/*
83 * Set up timer interrupt.
84 */
85static void __init ioc_timer_init(void)
86{
87    ioctime_init();
88    setup_irq(IRQ_TIMER, &ioc_timer_irq);
89}
90
91struct sys_timer ioc_timer = {
92    .init = ioc_timer_init,
93    .offset = ioc_timer_gettimeoffset,
94};
95
96

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