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
30static 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
65void __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
72static irqreturn_t
73ioc_timer_interrupt(int irq, void *dev_id)
74{
75	timer_tick();
76	return IRQ_HANDLED;
77}
78
79static struct irqaction ioc_timer_irq = {
80	.name		= "timer",
81	.handler	= ioc_timer_interrupt
82};
83
84/*
85 * Set up timer interrupt.
86 */
87void __init ioc_timer_init(void)
88{
89	arch_gettimeoffset = ioc_timer_gettimeoffset;
90	ioctime_init();
91	setup_irq(IRQ_TIMER0, &ioc_timer_irq);
92}
93