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/*
* linux/arch/arm/mach-sa1100/time.c
*
* Copyright (C) 1998 Deborah Wallach.
* Twiddles (C) 1999 Hugo Fiennes <hugo@empeg.com>
*
* 2000/03/29 (C) Nicolas Pitre <nico@cam.org>
* Rewritten: big cleanup, much simpler, better HZ accuracy.
*
*/
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/signal.h>
#include <asm/mach/time.h>
#include <asm/hardware.h>
#define RTC_DEF_DIVIDER (32768 - 1)
#define RTC_DEF_TRIM 0
static unsigned long __init sa1100_get_rtc_time(void)
{
/*
* According to the manual we should be able to let RTTR be zero
* and then a default diviser for a 32.768KHz clock is used.
* Apparently this doesn't work, at least for my SA1110 rev 5.
* If the clock divider is uninitialized then reset it to the
* default value to get the 1Hz clock.
*/
if (RTTR == 0) {
RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16);
printk(KERN_WARNING "Warning: uninitialized Real Time Clock\n");
/* The current RTC value probably doesn't make sense either */
RCNR = 0;
return 0;
}
return RCNR;
}
static int sa1100_set_rtc(void)
{
unsigned long current_time = xtime.tv_sec;
if (RTSR & RTSR_ALE) {
/* make sure not to forward the clock over an alarm */
unsigned long alarm = RTAR;
if (current_time >= alarm && alarm >= RCNR)
return -ERESTARTSYS;
}
RCNR = current_time;
return 0;
}
/* IRQs are disabled before entering here from do_gettimeofday() */
static unsigned long sa1100_gettimeoffset (void)
{
unsigned long ticks_to_match, elapsed, usec;
/* Get ticks before next timer match */
ticks_to_match = OSMR0 - OSCR;
/* We need elapsed ticks since last match */
elapsed = LATCH - ticks_to_match;
/* Now convert them to usec */
usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH;
return usec;
}
static irqreturn_t
sa1100_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
unsigned int next_match;
write_seqlock(&xtime_lock);
/*
* Loop until we get ahead of the free running timer.
* This ensures an exact clock tick count and time accuracy.
* Since IRQs are disabled at this point, coherence between
* lost_ticks(updated in do_timer()) and the match reg value is
* ensured, hence we can use do_gettimeofday() from interrupt
* handlers.
*/
do {
timer_tick(regs);
OSSR = OSSR_M0; /* Clear match on timer 0 */
next_match = (OSMR0 += LATCH);
} while ((signed long)(next_match - OSCR) <= 0);
write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}
static struct irqaction sa1100_timer_irq = {
.name = "SA11xx Timer Tick",
.flags = SA_INTERRUPT | SA_TIMER,
.handler = sa1100_timer_interrupt,
};
static void __init sa1100_timer_init(void)
{
struct timespec tv;
set_rtc = sa1100_set_rtc;
tv.tv_nsec = 0;
tv.tv_sec = sa1100_get_rtc_time();
do_settimeofday(&tv);
OSMR0 = 0; /* set initial match at 0 */
OSSR = 0xf; /* clear status on all timers */
setup_irq(IRQ_OST0, &sa1100_timer_irq);
OIER |= OIER_E0; /* enable match on timer 0 to cause interrupts */
OSCR = 0; /* initialize free-running timer, force first match */
}
#ifdef CONFIG_PM
unsigned long osmr[4], oier;
static void sa1100_timer_suspend(void)
{
osmr[0] = OSMR0;
osmr[1] = OSMR1;
osmr[2] = OSMR2;
osmr[3] = OSMR3;
oier = OIER;
}
static void sa1100_timer_resume(void)
{
OSSR = 0x0f;
OSMR0 = osmr[0];
OSMR1 = osmr[1];
OSMR2 = osmr[2];
OSMR3 = osmr[3];
OIER = oier;
/*
* OSMR0 is the system timer: make sure OSCR is sufficiently behind
*/
OSCR = OSMR0 - LATCH;
}
#else
#define sa1100_timer_suspend NULL
#define sa1100_timer_resume NULL
#endif
struct sys_timer sa1100_timer = {
.init = sa1100_timer_init,
.suspend = sa1100_timer_suspend,
.resume = sa1100_timer_resume,
.offset = sa1100_gettimeoffset,
};
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