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ARM: S3C: PWM fix for low duty cycle

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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>
This commit is contained in:
Peter Korsgaard 2009-07-01 17:47:08 +02:00 committed by Ben Dooks
parent 9b71de49b0
commit 165f5f6419
1 changed files with 4 additions and 0 deletions
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4
arch/arm/plat-s3c24xx/pwm.c
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@ -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);