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Commit 2b8aea74 authored by Chris Zankel's avatar Chris Zankel
Browse files

[XTENSA] Fix timer instabilities. 



The timer code could have missed a tick.

Signed-off-by: default avatarChris Zankel <chris@zankel.net>
parent bc671aa9

arch/xtensa/kernel/time.c

+29 −17
Original line number Diff line number Diff line
@@ -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)

		;
@@ -158,10 +171,13 @@ again: 


		write_seqlock(&xtime_lock);



		last_ccount_stamp = next;

		next += CCOUNT_PER_JIFFY;

		do_timer(1); /* Linux handler in kernel/timer.c */



		/* Note that writing CCOMPARE clears the interrupt. */



		next += CCOUNT_PER_JIFFY;

		set_linux_timer(next);



		if (ntp_synced() &&

		    xtime.tv_sec - last_rtc_update >= 659 &&

		    abs((xtime.tv_nsec/1000)-(1000000-1000000/HZ))<5000000/HZ) {
@@ -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;

}

include/asm-xtensa/timex.h

+2 −2
Original line number Diff line number Diff line
@@ -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