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/*
* arch/arm/mach-pxa/time.c
*
* Author: Nicolas Pitre
* Created: Jun 15, 2001
* Copyright: MontaVista Software Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <asm/system.h>
#include <asm/hardware.h>
#include <asm/io.h>
#include <asm/leds.h>
#include <asm/irq.h>
#include <asm/mach/irq.h>
#include <asm/mach/time.h>
#include <asm/arch/pxa-regs.h>
static inline unsigned long pxa_get_rtc_time(void)
{
return RCNR;
}
static int pxa_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 pxa_gettimeoffset (void)
{
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;
/* don't get fooled by the workaround in pxa_timer_interrupt() */
if (elapsed <= 0)
return 0;
/* Now convert them to usec */
usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH;
return usec;
}
static irqreturn_t
pxa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
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.
* 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.
*
* HACK ALERT: it seems that the PXA timer regs aren't updated right
* away in all cases when a write occurs. We therefore compare with
* 8 instead of 0 in the while() condition below to avoid missing a
* match if OSCR has already reached the next OSMR value.
* Experience has shown that up to 6 ticks are needed to work around
* this problem, but let's use 8 to be conservative. Note that this
* affect things only when the timer IRQ has been delayed by nearly
* exactly one tick period which should be a pretty rare event.
*/
do {
timer_tick(regs);
OSSR = OSSR_M0; /* Clear match on timer 0 */
next_match = (OSMR0 += LATCH);
} while( (signed long)(next_match - OSCR) <= 8 );
write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}
static struct irqaction pxa_timer_irq = {
.name = "PXA Timer Tick",
.flags = SA_INTERRUPT,
.handler = pxa_timer_interrupt
};
static void __init pxa_timer_init(void)
{
struct timespec tv;
set_rtc = pxa_set_rtc;
tv.tv_nsec = 0;
tv.tv_sec = pxa_get_rtc_time();
do_settimeofday(&tv);
OSMR0 = 0; /* set initial match at 0 */
OSSR = 0xf; /* clear status on all timers */
setup_irq(IRQ_OST0, &pxa_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
static unsigned long osmr[4], oier;
static void pxa_timer_suspend(void)
{
osmr[0] = OSMR0;
osmr[1] = OSMR1;
osmr[2] = OSMR2;
osmr[3] = OSMR3;
oier = OIER;
}
static void pxa_timer_resume(void)
{
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 pxa_timer_suspend NULL
#define pxa_timer_resume NULL
#endif
struct sys_timer pxa_timer = {
.init = pxa_timer_init,
.suspend = pxa_timer_suspend,
.resume = pxa_timer_resume,
.offset = pxa_gettimeoffset,
};
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