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Commit 023796b9 authored by Rob Herring's avatar Rob Herring
Browse files

ARM: arch_timer: use full 64-bit counter for sched_clock 



Only 32-bits of the arch timer were being used and wrapping was needlessly
being done in s/w. By using the full counter (56-64 bits), we don't need
to deal with wrapping and can simplify the implementation when using
arch timer.

Signed-off-by: default avatarRob Herring <rob.herring@calxeda.com>
parent 7e48c0b9

arch/arm/kernel/arch_timer.c

+13 −5
Original line number Original line Diff line number Diff line
@@ -22,9 +22,11 @@ static unsigned long arch_timer_read_counter_long(void) 
	return arch_timer_read_counter();

	return arch_timer_read_counter();

}

}





static u32 arch_timer_read_counter_u32(void)

static u32 sched_clock_mult __read_mostly;



static unsigned long long notrace arch_timer_sched_clock(void)

{

{

	return arch_timer_read_counter();

	return arch_timer_read_counter() * sched_clock_mult;

}

}





static struct delay_timer arch_delay_timer;

static struct delay_timer arch_delay_timer;
@@ -52,10 +54,16 @@ int __init arch_timer_of_register(void) 




int __init arch_timer_sched_clock_init(void)

int __init arch_timer_sched_clock_init(void)

{

{

	if (arch_timer_get_rate() == 0)

        u32 arch_timer_rate = arch_timer_get_rate();



	if (arch_timer_rate == 0)

		return -ENXIO;

		return -ENXIO;





	setup_sched_clock(arch_timer_read_counter_u32,

	/* Cache the sched_clock multiplier to save a divide in the hot path. */

			  32, arch_timer_get_rate());

	sched_clock_mult = NSEC_PER_SEC / arch_timer_rate;

	sched_clock_func = arch_timer_sched_clock;

	pr_info("sched_clock: ARM arch timer >56 bits at %ukHz, resolution %uns\n",

		arch_timer_rate / 1000, sched_clock_mult);



	return 0;

	return 0;

}
 
}