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Subject[PATCH 7/18] ARM: OMAP: Avoid updating system time for sub-jiffy interrupts
Date
Updating system time and reprogramming timer can cause latency
issues on busy systems with lots of interrupts with constant
updating of time and reprogramming the system timer.

If a non-timer dyntick interrupt happens within a jiffy from
the last interrupt, updating time and reprogramming the timer
is unnecessary as we will get a timer interrupt soon anyways.

Signed-off-by: Tony Lindgren <tony@atomide.com>
---
arch/arm/plat-omap/timer32k.c | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)

--- a/arch/arm/plat-omap/timer32k.c
+++ b/arch/arm/plat-omap/timer32k.c
@@ -219,6 +219,17 @@ static inline irqreturn_t _omap_32k_timer_interrupt(int irq, void *dev_id)

static irqreturn_t omap_32k_timer_handler(int irq, void *dev_id)
{
+ unsigned long now;
+
+ now = omap_32k_sync_timer_read();
+
+ /* Don't bother reprogramming timer if last tick was before next
+ * jiffie. We will get another interrupt when previously programmed
+ * timer expires. This cuts down interrupt load quite a bit.
+ */
+ if (now - omap_32k_last_tick < OMAP_32K_TICKS_PER_HZ)
+ return IRQ_HANDLED;
+
return _omap_32k_timer_interrupt(irq, dev_id);
}

--
1.4.4.2
-
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