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[XTENSA] Fix timer instabilities. 

The timer code could have missed a tick.

Signed-off-by: Chris Zankel <chris@zankel.net>
This commit is contained in:
Chris Zankel 2007-08-05 10:26:30 -07:00
parent bc671aa983
commit 2b8aea74e7
2 changed files with 31 additions and 19 deletions
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46
arch/xtensa/kernel/time.c
View File

@ -32,12 +32,20 @@ EXPORT_SYMBOL(rtc_lock);
#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
unsigned long ccount_per_jiffy; /* per 1/HZ */
unsigned long ccount_nsec; /* nsec per ccount increment */
unsigned long nsec_per_ccount; /* nsec per ccount increment */
#endif
unsigned int last_ccount_stamp;
static long last_rtc_update = 0;
/*
* Scheduler clock - returns current tim in nanosec units.
*/
unsigned long long sched_clock(void)
{
return (unsigned long long)jiffies * (1000000000 / HZ);
}
static irqreturn_t timer_interrupt(int irq, void *dev_id);
static struct irqaction timer_irqaction = {
.handler = timer_interrupt,
@ -69,7 +77,6 @@ void __init time_init(void)
xtime.tv_nsec = 0;
last_rtc_update = xtime.tv_sec = sec_n;
last_ccount_stamp = get_ccount();
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
@ -85,7 +92,7 @@ int do_settimeofday(struct timespec *tv)
{
time_t wtm_sec, sec = tv->tv_sec;
long wtm_nsec, nsec = tv->tv_nsec;
unsigned long ccount;
unsigned long delta;
if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
@ -97,8 +104,10 @@ int do_settimeofday(struct timespec *tv)
* wall time. Discover what correction gettimeofday() would have
* made, and then undo it!
*/
ccount = get_ccount();
nsec -= (ccount - last_ccount_stamp) * CCOUNT_NSEC;
delta = CCOUNT_PER_JIFFY;
delta += get_ccount() - get_linux_timer();
nsec -= delta * NSEC_PER_CCOUNT;
wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
@ -117,17 +126,21 @@ EXPORT_SYMBOL(do_settimeofday);
void do_gettimeofday(struct timeval *tv)
{
unsigned long flags;
unsigned long sec, usec, delta, seq;
unsigned long volatile sec, usec, delta, seq;
do {
seq = read_seqbegin_irqsave(&xtime_lock, flags);
delta = get_ccount() - last_ccount_stamp;
sec = xtime.tv_sec;
usec = (xtime.tv_nsec / NSEC_PER_USEC);
delta = get_linux_timer() - get_ccount();
} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
usec += (delta * CCOUNT_NSEC) / NSEC_PER_USEC;
usec += (((unsigned long) CCOUNT_PER_JIFFY - delta)
* (unsigned long) NSEC_PER_CCOUNT) / NSEC_PER_USEC;
for (; usec >= 1000000; sec++, usec -= 1000000)
;
@ -158,9 +171,12 @@ again:
write_seqlock(&xtime_lock);
last_ccount_stamp = next;
do_timer(1); /* Linux handler in kernel/timer.c */
/* Note that writing CCOMPARE clears the interrupt. */
next += CCOUNT_PER_JIFFY;
do_timer (1); /* Linux handler in kernel/timer.c */
set_linux_timer(next);
if (ntp_synced() &&
xtime.tv_sec - last_rtc_update >= 659 &&
@ -175,19 +191,15 @@ again:
write_sequnlock(&xtime_lock);
}
/* NOTE: writing CCOMPAREn clears the interrupt. */
/* Allow platform to do something useful (Wdog). */
set_linux_timer (next);
platform_heartbeat();
/* Make sure we didn't miss any tick... */
if ((signed long)(get_ccount() - next) > 0)
goto again;
/* Allow platform to do something useful (Wdog). */
platform_heartbeat();
return IRQ_HANDLED;
}

4
include/asm-xtensa/timex.h
View File

@ -41,10 +41,10 @@
extern unsigned long ccount_per_jiffy;
extern unsigned long ccount_nsec;
#define CCOUNT_PER_JIFFY ccount_per_jiffy
#define CCOUNT_NSEC ccount_nsec
#define NSEC_PER_CCOUNT ccount_nsec
#else
#define CCOUNT_PER_JIFFY (CONFIG_XTENSA_CPU_CLOCK*(1000000UL/HZ))
#define CCOUNT_NSEC (1000000000UL / CONFIG_XTENSA_CPU_CLOCK)
#define NSEC_PER_CCOUNT (1000UL / CONFIG_XTENSA_CPU_CLOCK)
#endif