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clocksource: samsung_pwm_timer: Work around rounding errors in clockevents core

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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>
This commit is contained in:
Tomasz Figa 2013-04-23 17:46:30 +02:00 committed by Olof Johansson
parent 6fe4dfd041
commit 81d4f7bfdc
1 changed files with 13 additions and 0 deletions
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13
drivers/clocksource/samsung_pwm_timer.c
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@ -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);