Commit fcc8f0f8 authored by Johannes Weiner's avatar Johannes Weiner Committed by Chris Zankel
Browse files

xtensa: ccount clocksource 



Switch to GENERIC_TIME by using the ccount register as a clock source.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarChris Zankel <chris@zankel.net>
parent 4476c967

arch/xtensa/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -48,6 +48,9 @@ config HZ 
	int

	default 100



config GENERIC_TIME

	def_bool y



source "init/Kconfig"

source "kernel/Kconfig.freezer"

arch/xtensa/kernel/time.c

+30 −73
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 


#include <linux/errno.h>

#include <linux/time.h>

#include <linux/clocksource.h>

#include <linux/interrupt.h>

#include <linux/module.h>

#include <linux/init.h>
@@ -29,6 +30,26 @@ unsigned long ccount_per_jiffy; /* per 1/HZ */ 
unsigned long nsec_per_ccount;		/* nsec per ccount increment */

#endif



static cycle_t ccount_read(void)

{

	return (cycle_t)get_ccount();

}



static struct clocksource ccount_clocksource = {

	.name = "ccount",

	.rating = 200,

	.read = ccount_read,

	.mask = CLOCKSOURCE_MASK(32),

	/*

	 * With a shift of 22 the lower limit of the cpu clock is

	 * 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than

	 * 2^10: Since we have 32 bits and the multiplicator can

	 * already take up as much as 10 bits, this leaves us with

	 * remaining upper 22 bits.

	 */

	.shift = 22,

};



static irqreturn_t timer_interrupt(int irq, void *dev_id);

static struct irqaction timer_irqaction = {

	.handler =	timer_interrupt,
@@ -38,9 +59,11 @@ static struct irqaction timer_irqaction = { 


void __init time_init(void)

{

	/* The platform must provide a function to calibrate the processor

	 * speed for the CALIBRATE.

	 */

	xtime.tv_nsec = 0;

	xtime.tv_sec = read_persistent_clock();



	set_normalized_timespec(&wall_to_monotonic,

		-xtime.tv_sec, -xtime.tv_nsec);



#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT

	printk("Calibrating CPU frequency ");
@@ -48,12 +71,10 @@ void __init time_init(void) 
	printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),

			(int)(ccount_per_jiffy/(10000/HZ))%100);

#endif



	xtime.tv_nsec = 0;

	xtime.tv_sec = read_persistent_clock();



	set_normalized_timespec(&wall_to_monotonic,

		-xtime.tv_sec, -xtime.tv_nsec);

	ccount_clocksource.mult =

		clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,

				ccount_clocksource.shift);

	clocksource_register(&ccount_clocksource);



	/* Initialize the linux timer interrupt. */
@@ -61,69 +82,6 @@ void __init time_init(void) 
	set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);

}





int do_settimeofday(struct timespec *tv)

{

	time_t wtm_sec, sec = tv->tv_sec;

	long wtm_nsec, nsec = tv->tv_nsec;

	unsigned long delta;



	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)

		return -EINVAL;



	write_seqlock_irq(&xtime_lock);



	/* This is revolting. We need to set "xtime" correctly. However, the

	 * value in this location is the value at the most recent update of

	 * wall time.  Discover what correction gettimeofday() would have

	 * made, and then undo it!

	 */



	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);



	set_normalized_timespec(&xtime, sec, nsec);

	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);



	ntp_clear();

	write_sequnlock_irq(&xtime_lock);

	return 0;

}



EXPORT_SYMBOL(do_settimeofday);





void do_gettimeofday(struct timeval *tv)

{

	unsigned long flags;

	unsigned long volatile sec, usec, delta, seq;



	do {

		seq = read_seqbegin_irqsave(&xtime_lock, flags);



		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 += (((unsigned long) CCOUNT_PER_JIFFY - delta)

		 * (unsigned long) NSEC_PER_CCOUNT) / NSEC_PER_USEC;



	for (; usec >= 1000000; sec++, usec -= 1000000)

		;



	tv->tv_sec = sec;

	tv->tv_usec = usec;

}



EXPORT_SYMBOL(do_gettimeofday);



/*

 * The timer interrupt is called HZ times per second.

 */
@@ -177,4 +135,3 @@ void __cpuinit calibrate_delay(void) 
	       (loops_per_jiffy/(10000/HZ)) % 100);

}

#endif