[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: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-at91rm9200/time.c b/arch/arm/mach-at91rm9200/time.c
index 7ffcf44..36798a8 100644
--- a/arch/arm/mach-at91rm9200/time.c
+++ b/arch/arm/mach-at91rm9200/time.c
@@ -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 @@
{
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 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 struct irqaction at91rm9200_timer_irq = {
.name = "at91_tick",
- .flags = SA_SHIRQ | SA_INTERRUPT,
+ .flags = SA_SHIRQ | SA_INTERRUPT | SA_TIMER,
.handler = at91rm9200_timer_interrupt
};