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Commit 8a3269fc authored by Stefan Agner's avatar Stefan Agner Committed by Nicolas Pitre
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[ARM] orion: sched_clock implementation for orion platforms 



sched_clock implementation for orion platform. Its realized using
free-running clocksource timer, which provides a resolution of 7.5ns
(depending on tclk). It's derived from PXA's sched_clock implementation.

[ nico: renamed orion2ns to tclk2ns, fixed max value in the comment ]

Signed-off-by: default avatarStefan Agner <stefan.agner@yahoo.com>
Signed-off-by: default avatarNicolas Pitre <nico@marvell.com>
parent e50b6bef

arch/arm/plat-orion/time.c

+37 −0
Original line number Diff line number Diff line
@@ -17,6 +17,9 @@ 
#include <linux/irq.h>

#include <asm/mach/time.h>

#include <mach/bridge-regs.h>

#include <mach/hardware.h>

#include <linux/sched.h>

#include <linux/cnt32_to_63.h>



/*

 * Number of timer ticks per jiffy.
@@ -38,6 +41,36 @@ static u32 ticks_per_jiffy; 
#define TIMER1_VAL		(TIMER_VIRT_BASE + 0x001c)





/*

 * Orion's sched_clock implementation. It has a resolution of

 * at least 7.5ns (133MHz TCLK) and a maximum value of 834 days.

 */

#define TCLK2NS_SCALE_FACTOR 8



static unsigned long tclk2ns_scale;



static void __init set_tclk2ns_scale(unsigned long tclk)

{

	unsigned long long v = NSEC_PER_SEC;

	v <<= TCLK2NS_SCALE_FACTOR;

	v += tclk/2;

	do_div(v, tclk);

	/*

	 * We want an even value to automatically clear the top bit

	 * returned by cnt32_to_63() without an additional run time

	 * instruction. So if the LSB is 1 then round it up.

	 */

	if (v & 1)

		v++;

	tclk2ns_scale = v;

}



unsigned long long sched_clock(void)

{

	unsigned long long v = cnt32_to_63(0xffffffff - readl(TIMER0_VAL));

	return (v * tclk2ns_scale) >> TCLK2NS_SCALE_FACTOR;

}



/*

 * Clocksource handling.

 */
@@ -176,6 +209,10 @@ void __init orion_time_init(unsigned int irq, unsigned int tclk) 


	ticks_per_jiffy = (tclk + HZ/2) / HZ;



	/*

	 * Set scale for sched_clock

	 */

	set_tclk2ns_scale(tclk);



	/*

	 * Setup free-running clocksource timer (interrupts