forked from Minki/linux
0cd61b68c3
Untested, but this should fix up the bulk of the totally mechanical issues, and should make the actual detail fixing easier. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
96 lines
2.1 KiB
C
96 lines
2.1 KiB
C
/*
|
|
* linux/arch/arm/mach-footbridge/isa-timer.c
|
|
*
|
|
* Copyright (C) 1998 Russell King.
|
|
* Copyright (C) 1998 Phil Blundell
|
|
*/
|
|
#include <linux/init.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/irq.h>
|
|
|
|
#include <asm/io.h>
|
|
#include <asm/irq.h>
|
|
|
|
#include <asm/mach/time.h>
|
|
|
|
#include "common.h"
|
|
|
|
/*
|
|
* ISA timer tick support
|
|
*/
|
|
#define mSEC_10_from_14 ((14318180 + 100) / 200)
|
|
|
|
static unsigned long isa_gettimeoffset(void)
|
|
{
|
|
int count;
|
|
|
|
static int count_p = (mSEC_10_from_14/6); /* for the first call after boot */
|
|
static unsigned long jiffies_p = 0;
|
|
|
|
/*
|
|
* cache volatile jiffies temporarily; we have IRQs turned off.
|
|
*/
|
|
unsigned long jiffies_t;
|
|
|
|
/* timer count may underflow right here */
|
|
outb_p(0x00, 0x43); /* latch the count ASAP */
|
|
|
|
count = inb_p(0x40); /* read the latched count */
|
|
|
|
/*
|
|
* We do this guaranteed double memory access instead of a _p
|
|
* postfix in the previous port access. Wheee, hackady hack
|
|
*/
|
|
jiffies_t = jiffies;
|
|
|
|
count |= inb_p(0x40) << 8;
|
|
|
|
/* Detect timer underflows. If we haven't had a timer tick since
|
|
the last time we were called, and time is apparently going
|
|
backwards, the counter must have wrapped during this routine. */
|
|
if ((jiffies_t == jiffies_p) && (count > count_p))
|
|
count -= (mSEC_10_from_14/6);
|
|
else
|
|
jiffies_p = jiffies_t;
|
|
|
|
count_p = count;
|
|
|
|
count = (((mSEC_10_from_14/6)-1) - count) * (tick_nsec / 1000);
|
|
count = (count + (mSEC_10_from_14/6)/2) / (mSEC_10_from_14/6);
|
|
|
|
return count;
|
|
}
|
|
|
|
static irqreturn_t
|
|
isa_timer_interrupt(int irq, void *dev_id)
|
|
{
|
|
write_seqlock(&xtime_lock);
|
|
timer_tick();
|
|
write_sequnlock(&xtime_lock);
|
|
return IRQ_HANDLED;
|
|
}
|
|
|
|
static struct irqaction isa_timer_irq = {
|
|
.name = "ISA timer tick",
|
|
.handler = isa_timer_interrupt,
|
|
.flags = IRQF_DISABLED | IRQF_TIMER,
|
|
};
|
|
|
|
static void __init isa_timer_init(void)
|
|
{
|
|
isa_rtc_init();
|
|
|
|
/* enable PIT timer */
|
|
/* set for periodic (4) and LSB/MSB write (0x30) */
|
|
outb(0x34, 0x43);
|
|
outb((mSEC_10_from_14/6) & 0xFF, 0x40);
|
|
outb((mSEC_10_from_14/6) >> 8, 0x40);
|
|
|
|
setup_irq(IRQ_ISA_TIMER, &isa_timer_irq);
|
|
}
|
|
|
|
struct sys_timer isa_timer = {
|
|
.init = isa_timer_init,
|
|
.offset = isa_gettimeoffset,
|
|
};
|