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Commit 2dc20a51 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
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[ARM] 3981/1: sched_clock for PXA2xx 



Here's a 63-bit implementation of shed_clock() for PXA2xx.  The actual
period depends on the value of CLOCK_TICK_RATE and whether or not
reduced scaling factors were provided for it.

Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 752bee17

arch/arm/mach-pxa/generic.c

+60 −0
Original line number Diff line number Diff line
@@ -25,6 +25,10 @@ 
#include <linux/pm.h>

#include <linux/string.h>



#include <linux/sched.h>

#include <asm/cnt32_to_63.h>

#include <asm/div64.h>



#include <asm/hardware.h>

#include <asm/irq.h>

#include <asm/system.h>
@@ -40,6 +44,62 @@ 


#include "generic.h"



/*

 * This is the PXA2xx sched_clock implementation. This has a resolution

 * of at least 308ns and a maximum value that depends on the value of

 * CLOCK_TICK_RATE.

 *

 * The return value is guaranteed to be monotonic in that range as

 * long as there is always less than 582 seconds between successive

 * calls to this function.

 */

unsigned long long sched_clock(void)

{

	unsigned long long v = cnt32_to_63(OSCR);

	/* Note: top bit ov v needs cleared unless multiplier is even. */



#if	CLOCK_TICK_RATE == 3686400

	/* 1E9 / 3686400 => 78125 / 288, max value = 32025597s (370 days). */

	/* The <<1 is used to get rid of tick.hi top bit */

	v *= 78125<<1;

	do_div(v, 288<<1);

#elif	CLOCK_TICK_RATE == 3250000

	/* 1E9 / 3250000 => 4000 / 13, max value = 709490156s (8211 days) */

	v *= 4000;

	do_div(v, 13);

#elif	CLOCK_TICK_RATE == 3249600

	/* 1E9 / 3249600 => 625000 / 2031, max value = 4541295s (52 days) */

	v *= 625000;

	do_div(v, 2031);

#else

#warning "consider fixing sched_clock for your value of CLOCK_TICK_RATE"

	/*

	 * 96-bit math to perform tick * NSEC_PER_SEC / CLOCK_TICK_RATE for

	 * any value of CLOCK_TICK_RATE. Max value is in the 80 thousand

	 * years range which is nice, but with higher computation cost.

	 */

	{

		union {

			unsigned long long val;

			struct { unsigned long lo, hi; };

		} x;

		unsigned long long y;



		x.val = v;

		x.hi &= 0x7fffffff;

		y = (unsigned long long)x.lo * NSEC_PER_SEC;

		x.lo = y;

		y = (y >> 32) + (unsigned long long)x.hi * NSEC_PER_SEC;

		x.hi = do_div(y, CLOCK_TICK_RATE);

		do_div(x.val, CLOCK_TICK_RATE);

		x.hi += y;

		v = x.val;

	}

#endif



	return v;

}



/*

 * Handy function to set GPIO alternate functions

 */