xref: /openbmc/linux/arch/arm/mach-rpc/time.c (revision e23feb16)
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 static u32 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) * 1000;
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 	timer_tick();
73 	return IRQ_HANDLED;
74 }
75 
76 static 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  */
85 void __init ioc_timer_init(void)
86 {
87 	arch_gettimeoffset = ioc_timer_gettimeoffset;
88 	ioctime_init();
89 	setup_irq(IRQ_TIMER0, &ioc_timer_irq);
90 }
91