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[ARM] 3579/1: AT91RM9200 Timer simplification

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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: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Andrew Victor 2006-06-19 15:23:41 +01:00 committed by Russell King
parent 91f8ed835f
commit 963151f247
1 changed files with 6 additions and 7 deletions
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13
arch/arm/mach-at91rm9200/time.c
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@ -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
};