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Commit 963151f2 authored by Andrew Victor's avatar Andrew Victor Committed by Russell King
Browse files

[ARM] 3579/1: AT91RM9200 Timer simplification 



Patch from Andrew Victor

Use a global variable 'last_crtr' to store the time of the last timer
tick instead of the ST_RTAR register.
It's faster, frees up the ST_RTAR register for other uses, and hopefully
makes the code more understandable.  [Patch from Peter Menzebach]

Also add the SA_TIMER flag to Timer IRQ.  (It seems to be required for
the realtime preempt patch).

Signed-off-by: default avatarAndrew Victor <andrew@sanpeople.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 91f8ed83

arch/arm/mach-at91rm9200/time.c

+6 −7
Original line number Diff line number Diff line
@@ -31,6 +31,8 @@ 
#include <asm/irq.h>

#include <asm/mach/time.h>



static unsigned long last_crtr;



/*

 * The ST_CRTR is updated asynchronously to the master clock.  It is therefore

 *  necessary to read it twice (with the same value) to ensure accuracy.
@@ -56,7 +58,7 @@ static unsigned long at91rm9200_gettimeoffset(void) 
{

	unsigned long elapsed;



	elapsed = (read_CRTR() - at91_sys_read(AT91_ST_RTAR)) & AT91_ST_ALMV;

	elapsed = (read_CRTR() - last_crtr) & AT91_ST_ALMV;



	return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;

}
@@ -66,15 +68,12 @@ static unsigned long at91rm9200_gettimeoffset(void) 
 */

static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)

{

	unsigned long rtar;



	if (at91_sys_read(AT91_ST_SR) & AT91_ST_PITS) {	/* This is a shared interrupt */

		write_seqlock(&xtime_lock);



		while (((read_CRTR() - at91_sys_read(AT91_ST_RTAR)) & AT91_ST_ALMV) >= LATCH) {

		while (((read_CRTR() - last_crtr) & AT91_ST_ALMV) >= LATCH) {

			timer_tick(regs);

			rtar = (at91_sys_read(AT91_ST_RTAR) + LATCH) & AT91_ST_ALMV;

			at91_sys_write(AT91_ST_RTAR, rtar);

			last_crtr = (last_crtr + LATCH) & AT91_ST_ALMV;

		}



		write_sequnlock(&xtime_lock);
@@ -87,7 +86,7 @@ static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id, struct pt_r 


static struct irqaction at91rm9200_timer_irq = {

	.name		= "at91_tick",

	.flags		= SA_SHIRQ | SA_INTERRUPT,

	.flags		= SA_SHIRQ | SA_INTERRUPT | SA_TIMER,

	.handler	= at91rm9200_timer_interrupt

};