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Commit a1b2dde7 authored by Marc Zyngier's avatar Marc Zyngier Committed by Russell King
Browse files

ARM: 7522/1: arch_timers: register a time/cycle counter 



Some subsystems (KVM for example) need access to a cycle counter.
In the KVM case, this is used to measure the time delta between
host and guest in order to accurately generate timer events for
the guest.

Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent f48b5f12

arch/arm/include/asm/arch_timer.h

+7 −0
Original line number Diff line number Diff line
@@ -2,11 +2,13 @@ 
#define __ASMARM_ARCH_TIMER_H



#include <asm/errno.h>

#include <linux/clocksource.h>



#ifdef CONFIG_ARM_ARCH_TIMER

#define ARCH_HAS_READ_CURRENT_TIMER

int arch_timer_of_register(void);

int arch_timer_sched_clock_init(void);

struct timecounter *arch_timer_get_timecounter(void);

#else

static inline int arch_timer_of_register(void)

{
@@ -17,6 +19,11 @@ static inline int arch_timer_sched_clock_init(void) 
{

	return -ENXIO;

}



static inline struct timecounter *arch_timer_get_timecounter(void)

{

	return NULL;

}

#endif



#endif

arch/arm/kernel/arch_timer.c

+25 −0
Original line number Diff line number Diff line
@@ -333,6 +333,15 @@ int read_current_timer(unsigned long *timer_val) 
	return 0;

}



static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)

{

	/*

	 * Always use the physical counter for the clocksource.

	 * CNTHCTL.PL1PCTEN must be set to 1.

	 */

	return arch_counter_get_cntpct();

}



static struct clocksource clocksource_counter = {

	.name	= "arch_sys_counter",

	.rating	= 400,
@@ -341,6 +350,18 @@ static struct clocksource clocksource_counter = { 
	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,

};



static struct cyclecounter cyclecounter = {

	.read	= arch_counter_read_cc,

	.mask	= CLOCKSOURCE_MASK(56),

};



static struct timecounter timecounter;



struct timecounter *arch_timer_get_timecounter(void)

{

	return &timecounter;

}



static void __cpuinit arch_timer_stop(struct clock_event_device *clk)

{

	pr_debug("arch_timer_teardown disable IRQ%d cpu #%d\n",
@@ -380,6 +401,10 @@ static int __init arch_timer_register(void) 
	}



	clocksource_register_hz(&clocksource_counter, arch_timer_rate);

	cyclecounter.mult = clocksource_counter.mult;

	cyclecounter.shift = clocksource_counter.shift;

	timecounter_init(&timecounter, &cyclecounter,

			 arch_counter_get_cntpct());



	if (arch_timer_use_virtual) {

		ppi = arch_timer_ppi[VIRT_PPI];