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[ARM] orion: sched_clock implementation for orion platforms

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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: Stefan Agner <stefan.agner@yahoo.com>
Signed-off-by: Nicolas Pitre <nico@marvell.com>
This commit is contained in:
Stefan Agner 2009-05-12 10:30:41 -07:00 committed by Nicolas Pitre
parent e50b6befae
commit 8a3269fc21
1 changed files with 37 additions and 0 deletions
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37
arch/arm/plat-orion/time.c
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@ -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