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Commit 2f1675c1 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
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[ARM] 3979/1: extend the SA11x0 sched_clock implementation from 32 to 63 bit period 



This provides a 63 bit clock counter guaranteed to be monotonic over a
period of 370 days instead of a clock wrap every 19.4 minutes, as long
as sched_clock() is called at least once every 9.7 minutes which
shouldn't be a problem in practice.

Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 838ccbc3

arch/arm/mach-sa1100/generic.c

+11 −4
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/platform_device.h>



#include <asm/div64.h>

#include <asm/cnt32_to_63.h>

#include <asm/hardware.h>

#include <asm/system.h>

#include <asm/pgtable.h>
@@ -118,15 +119,21 @@ EXPORT_SYMBOL(cpufreq_get); 


/*

 * This is the SA11x0 sched_clock implementation.  This has

 * a resolution of 271ns, and a maximum value of 1165s.

 * a resolution of 271ns, and a maximum value of 32025597s (370 days).

 *

 * 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.

 *

 *  ( * 1E9 / 3686400 => * 78125 / 288)

 */

unsigned long long sched_clock(void)

{

	unsigned long long v;

	unsigned long long v = cnt32_to_63(OSCR);



	v = (unsigned long long)OSCR * 78125;

	do_div(v, 288);

	/* the <<1 gets rid of the cnt_32_to_63 top bit saving on a bic insn */

	v *= 78125<<1;

	do_div(v, 288<<1);



	return v;

}