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Commit 9ce34c8f authored by John Stultz's avatar John Stultz Committed by Matt Turner
Browse files

Convert alpha to use clocksources instead of arch_gettimeoffset 



Alpha has a tsc like rpcc counter that it uses to manage time.
This can be converted to an actual clocksource instead of utilizing
the arch_gettimeoffset method that is really only there for legacy
systems with no continuous counter.

Further cleanups could be made if alpha converted to the clockevent
model.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Henderson <rth@twiddle.net>
Acked-by: default avatarIvan Kokshaysky <ink@jurassic.park.msu.ru>
Tested-by: default avatarIvan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: default avatarMatt Turner <mattst88@gmail.com>
Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
parent ec96e2fe

arch/alpha/Kconfig

+0 −4
Original line number Diff line number Diff line
@@ -51,10 +51,6 @@ config GENERIC_TIME 
	bool

	default y



config ARCH_USES_GETTIMEOFFSET

	bool

	default y



config GENERIC_CMOS_UPDATE

        def_bool y

arch/alpha/kernel/time.c

+31 −38
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ 
#include <linux/mc146818rtc.h>

#include <linux/time.h>

#include <linux/timex.h>

#include <linux/clocksource.h>



#include "proto.h"

#include "irq_impl.h"
@@ -332,6 +333,34 @@ rpcc_after_update_in_progress(void) 
	return rpcc();

}



#ifndef CONFIG_SMP

/* Until and unless we figure out how to get cpu cycle counters

   in sync and keep them there, we can't use the rpcc.  */

static cycle_t read_rpcc(struct clocksource *cs)

{

	cycle_t ret = (cycle_t)rpcc();

	return ret;

}



static struct clocksource clocksource_rpcc = {

	.name                   = "rpcc",

	.rating                 = 300,

	.read                   = read_rpcc,

	.mask                   = CLOCKSOURCE_MASK(32),

	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS

};



static inline void register_rpcc_clocksource(long cycle_freq)

{

	clocksource_calc_mult_shift(&clocksource_rpcc, cycle_freq, 4);

	clocksource_register(&clocksource_rpcc);

}

#else /* !CONFIG_SMP */

static inline void register_rpcc_clocksource(long cycle_freq)

{

}

#endif /* !CONFIG_SMP */



void __init

time_init(void)

{
@@ -385,6 +414,8 @@ time_init(void) 
		__you_loose();

	}



	register_rpcc_clocksource(cycle_freq);



	state.last_time = cc1;

	state.scaled_ticks_per_cycle

		= ((unsigned long) HZ << FIX_SHIFT) / cycle_freq;
@@ -394,44 +425,6 @@ time_init(void) 
	alpha_mv.init_rtc();

}



/*

 * Use the cycle counter to estimate an displacement from the last time

 * tick.  Unfortunately the Alpha designers made only the low 32-bits of

 * the cycle counter active, so we overflow on 8.2 seconds on a 500MHz

 * part.  So we can't do the "find absolute time in terms of cycles" thing

 * that the other ports do.

 */

u32 arch_gettimeoffset(void)

{

#ifdef CONFIG_SMP

	/* Until and unless we figure out how to get cpu cycle counters

	   in sync and keep them there, we can't use the rpcc tricks.  */

	return 0;

#else

	unsigned long delta_cycles, delta_usec, partial_tick;



	delta_cycles = rpcc() - state.last_time;

	partial_tick = state.partial_tick;

	/*

	 * usec = cycles * ticks_per_cycle * 2**48 * 1e6 / (2**48 * ticks)

	 *	= cycles * (s_t_p_c) * 1e6 / (2**48 * ticks)

	 *	= cycles * (s_t_p_c) * 15625 / (2**42 * ticks)

	 *

	 * which, given a 600MHz cycle and a 1024Hz tick, has a

	 * dynamic range of about 1.7e17, which is less than the

	 * 1.8e19 in an unsigned long, so we are safe from overflow.

	 *

	 * Round, but with .5 up always, since .5 to even is harder

	 * with no clear gain.

	 */



	delta_usec = (delta_cycles * state.scaled_ticks_per_cycle 

		      + partial_tick) * 15625;

	delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;

	return delta_usec * 1000;

#endif

}



/*

 * In order to set the CMOS clock precisely, set_rtc_mmss has to be

 * called 500 ms after the second nowtime has started, because when