Commit 165f5f64 authored Jul 01, 2009 by Peter Korsgaard Committed by Ben Dooks Jul 30, 2009

ARM: S3C: PWM fix for low duty cycle



The pwm hardware only checks the compare register after a decrement,
so the pin never toggles if tcmp = tcnt.

This happens when a very low duty cycle is requested. Fix it by always
ensuring that tcmp < tcnt.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

parent 9b71de49

arch/arm/plat-s3c24xx/pwm.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -246,6 +246,10 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)

		tcmp = duty_ns / tin_ns;
		tcmp = tcnt - tcmp;
		/* the pwm hw only checks the compare register after a decrement,
		so the pin never toggles if tcmp = tcnt */
		if (tcmp == tcnt)
		tcmp--;

		pwm_dbg(pwm, "tin_ns=%lu, tcmp=%ld/%lu\n", tin_ns, tcmp, tcnt);