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/*
* linux/include/asm-arm/arch-sa1100/time.h
*
* 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.
*
*/
#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)/LATCH;
return usec;
}
static void sa1100_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
long flags;
int next_match;
/* Loop until we get ahead of the free running timer.
* This ensures an exact clock tick count and time acuracy.
* IRQs are disabled inside the loop to ensure coherence between
* lost_ticks (updated in do_timer()) and the match reg value, so we
* can use do_gettimeofday() from interrupt handlers.
*/
do {
do_leds();
do_set_rtc();
save_flags_cli( flags );
do_timer(regs);
OSSR = OSSR_M0; /* Clear match on timer 0 */
next_match = (OSMR0 += LATCH);
restore_flags( flags );
} while( (signed long)(next_match - OSCR) <= 0 );
}
static inline void setup_timer (void)
{
gettimeoffset = sa1100_gettimeoffset;
set_rtc = sa1100_set_rtc;
xtime.tv_sec = sa1100_get_rtc_time();
timer_irq.handler = sa1100_timer_interrupt;
OSMR0 = 0; /* set initial match at 0 */
OSSR = 0xf; /* clear status on all timers */
setup_arm_irq(IRQ_OST0, &timer_irq);
OIER |= OIER_E0; /* enable match on timer 0 to cause interrupts */
OSCR = 0; /* initialize free-running timer, force first match */
}
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