[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>
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@ -31,6 +31,8 @@
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#include <asm/irq.h>
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#include <asm/mach/time.h>
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static unsigned long last_crtr;
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/*
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* The ST_CRTR is updated asynchronously to the master clock. It is therefore
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* necessary to read it twice (with the same value) to ensure accuracy.
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@ -56,7 +58,7 @@ static unsigned long at91rm9200_gettimeoffset(void)
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{
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unsigned long elapsed;
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elapsed = (read_CRTR() - at91_sys_read(AT91_ST_RTAR)) & AT91_ST_ALMV;
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elapsed = (read_CRTR() - last_crtr) & AT91_ST_ALMV;
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return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
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}
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@ -66,15 +68,12 @@ static unsigned long at91rm9200_gettimeoffset(void)
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*/
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static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
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{
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unsigned long rtar;
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if (at91_sys_read(AT91_ST_SR) & AT91_ST_PITS) { /* This is a shared interrupt */
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write_seqlock(&xtime_lock);
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while (((read_CRTR() - at91_sys_read(AT91_ST_RTAR)) & AT91_ST_ALMV) >= LATCH) {
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while (((read_CRTR() - last_crtr) & AT91_ST_ALMV) >= LATCH) {
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timer_tick(regs);
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rtar = (at91_sys_read(AT91_ST_RTAR) + LATCH) & AT91_ST_ALMV;
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at91_sys_write(AT91_ST_RTAR, rtar);
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last_crtr = (last_crtr + LATCH) & AT91_ST_ALMV;
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}
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write_sequnlock(&xtime_lock);
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@ -87,7 +86,7 @@ static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id, struct pt_r
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static struct irqaction at91rm9200_timer_irq = {
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.name = "at91_tick",
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.flags = SA_SHIRQ | SA_INTERRUPT,
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.flags = SA_SHIRQ | SA_INTERRUPT | SA_TIMER,
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.handler = at91rm9200_timer_interrupt
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};
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