From: Tomasz Figa Date: Tue, 23 Apr 2013 15:46:30 +0000 (+0200) Subject: clocksource: samsung_pwm_timer: Work around rounding errors in clockevents core X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=81d4f7bfdc9417e7d8fc1133c762daa4458eec5e;p=openwrt%2Fstaging%2Fblogic.git 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 Signed-off-by: Kyungmin Park Reviewed-by: Arnd Bergmann Acked-by: Kukjin Kim Signed-off-by: Olof Johansson --- diff --git a/drivers/clocksource/samsung_pwm_timer.c b/drivers/clocksource/samsung_pwm_timer.c index 92b2f130ae9b..0234c8d2c8f2 100644 --- a/drivers/clocksource/samsung_pwm_timer.c +++ b/drivers/clocksource/samsung_pwm_timer.c @@ -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);