Commit 81d4f7bf authored Apr 23, 2013 by Tomasz Figa Committed by Olof Johansson Apr 28, 2013

clocksource: samsung_pwm_timer: Work around rounding errors in clockevents core



Due to rounding errors in clockevents core (in conversions between ticks
and nsecs), it might happen that the set_next_event callback gets called
with cycles = 0, causing the code to incorrectly program the PWM timer.

This patch modifies the callback to program the timer for 1 tick, if
received tick count value is 0.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

parent 6fe4dfd0

drivers/clocksource/samsung_pwm_timer.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -176,6 +176,19 @@ static void samsung_time_start(unsigned int channel, bool periodic)
		static int samsung_set_next_event(unsigned long cycles,
		struct clock_event_device *evt)
		{
		/*
		* This check is needed to account for internal rounding
		* errors inside clockevents core, which might result in
		* passing cycles = 0, which in turn would not generate any
		* timer interrupt and hang the system.
		*
		* Another solution would be to set up the clockevent device
		* with min_delta = 2, but this would unnecessarily increase
		* the minimum sleep period.
		*/
		if (!cycles)
		cycles = 1;

		samsung_time_setup(pwm.event_id, cycles);
		samsung_time_start(pwm.event_id, false);