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Diffstat (limited to 'arch/arm/mach-footbridge/isa-timer.c')
-rw-r--r--arch/arm/mach-footbridge/isa-timer.c94
1 files changed, 94 insertions, 0 deletions
diff --git a/arch/arm/mach-footbridge/isa-timer.c b/arch/arm/mach-footbridge/isa-timer.c
new file mode 100644
index 000000000000..a4fefa0bb5a1
--- /dev/null
+++ b/arch/arm/mach-footbridge/isa-timer.c
@@ -0,0 +1,94 @@
1/*
2 * linux/arch/arm/mach-footbridge/isa-timer.c
3 *
4 * Copyright (C) 1998 Russell King.
5 * Copyright (C) 1998 Phil Blundell
6 */
7#include <linux/init.h>
8#include <linux/interrupt.h>
9
10#include <asm/io.h>
11#include <asm/irq.h>
12
13#include <asm/mach/time.h>
14
15#include "common.h"
16
17/*
18 * ISA timer tick support
19 */
20#define mSEC_10_from_14 ((14318180 + 100) / 200)
21
22static unsigned long isa_gettimeoffset(void)
23{
24 int count;
25
26 static int count_p = (mSEC_10_from_14/6); /* for the first call after boot */
27 static unsigned long jiffies_p = 0;
28
29 /*
30 * cache volatile jiffies temporarily; we have IRQs turned off.
31 */
32 unsigned long jiffies_t;
33
34 /* timer count may underflow right here */
35 outb_p(0x00, 0x43); /* latch the count ASAP */
36
37 count = inb_p(0x40); /* read the latched count */
38
39 /*
40 * We do this guaranteed double memory access instead of a _p
41 * postfix in the previous port access. Wheee, hackady hack
42 */
43 jiffies_t = jiffies;
44
45 count |= inb_p(0x40) << 8;
46
47 /* Detect timer underflows. If we haven't had a timer tick since
48 the last time we were called, and time is apparently going
49 backwards, the counter must have wrapped during this routine. */
50 if ((jiffies_t == jiffies_p) && (count > count_p))
51 count -= (mSEC_10_from_14/6);
52 else
53 jiffies_p = jiffies_t;
54
55 count_p = count;
56
57 count = (((mSEC_10_from_14/6)-1) - count) * (tick_nsec / 1000);
58 count = (count + (mSEC_10_from_14/6)/2) / (mSEC_10_from_14/6);
59
60 return count;
61}
62
63static irqreturn_t
64isa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
65{
66 write_seqlock(&xtime_lock);
67 timer_tick(regs);
68 write_sequnlock(&xtime_lock);
69 return IRQ_HANDLED;
70}
71
72static struct irqaction isa_timer_irq = {
73 .name = "ISA timer tick",
74 .handler = isa_timer_interrupt,
75 .flags = SA_INTERRUPT,
76};
77
78static void __init isa_timer_init(void)
79{
80 isa_rtc_init();
81
82 /* enable PIT timer */
83 /* set for periodic (4) and LSB/MSB write (0x30) */
84 outb(0x34, 0x43);
85 outb((mSEC_10_from_14/6) & 0xFF, 0x40);
86 outb((mSEC_10_from_14/6) >> 8, 0x40);
87
88 setup_irq(IRQ_ISA_TIMER, &isa_timer_irq);
89}
90
91struct sys_timer isa_timer = {
92 .init = isa_timer_init,
93 .offset = isa_gettimeoffset,
94};