[PATCH 41/90] ARM: OMAP: Avoid updating system time for sub-jiffy interrupts

Tony Lindgren
2007-04-04T18:31:08Z

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(-)

diff --git a/arch/arm/plat-omap/timer32k.c b/arch/arm/plat-omap/timer32k.c
index 2653106..c37d7b4 100644
--- 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