[PATCH 1/3] ARM: msm: Stop counting before reprogramming clockevent

Stephen Boyd sboyd at codeaurora.org
Thu Mar 14 23:31:37 EDT 2013

If the clockevent is forcibly reprogrammed to have a different
match value we mistakenly assume the timer is not ticking and
program a new match value while the timer is running. Although we
clear the timer before programming a new match, it's better to
stop the timer before clearing it so that we're sure the proper
amount of ticks are counted. Failure to do so can lead to missed
ticks and system hangs.

Signed-off-by: Stephen Boyd <sboyd at codeaurora.org>
 arch/arm/mach-msm/timer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-msm/timer.c b/arch/arm/mach-msm/timer.c
index 2969027..f9fd77e 100644
--- a/arch/arm/mach-msm/timer.c
+++ b/arch/arm/mach-msm/timer.c
@@ -62,7 +62,10 @@ static int msm_timer_set_next_event(unsigned long cycles,
 	u32 ctrl = readl_relaxed(event_base + TIMER_ENABLE);
-	writel_relaxed(0, event_base + TIMER_CLEAR);
+	ctrl &= ~TIMER_ENABLE_EN;
+	writel_relaxed(ctrl, event_base + TIMER_ENABLE);
+	writel_relaxed(ctrl, event_base + TIMER_CLEAR);
 	writel_relaxed(cycles, event_base + TIMER_MATCH_VAL);
 	writel_relaxed(ctrl | TIMER_ENABLE_EN, event_base + TIMER_ENABLE);
 	return 0;
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