On Wed, 2015-03-18 at 09:08 +0100, Lukasz Majewski wrote: > Hi Sjoerd, > > > Hey Jingoo, Kukjijn, Lukasz, > > > > Pinging on this one again, could you please review this patch so it > > can be merged through the PWM tree? > > As fair as I remember, I've already acked the patch :-) I don't think you did, but i might have missed it ofcourse. Seems patchwork also missed it though: https://patchwork.ozlabs.org/patch/446643/ Mind redoing you're acked-by so it gets picked up by patchwork ? :) > > > > On Thu, 2015-03-05 at 09:14 +0100, Sjoerd Simons wrote: > > > When disabling the samsung PWM the output state remains at the > > > level it was in the end of a pwm cycle. In other words, calling > > > pwm_disable when at 100% duty will keep the output active, while at > > > all other setting the output will go/stay inactive. On top of that > > > the samsung PWM settings are double-buffered, which means the new > > > settings only get applied at the start of a new PWM cycle. > > > > > > This results in a race if the PWM is at 100% duty and a driver > > > calls: pwm_config (pwm, 0, period); > > > pwm_disable (pwm); > > > > > > In this case the PWMs output will unexpectedly stay active, unless > > > a new PWM cycle happened to start between the register writes in > > > _config and _disable. As far as i can tell this is a regression > > > introduced by 3bdf878, before that a call to pwm_config would call > > > pwm_samsung_enable which, while heavy-handed, made sure the > > > expected settings were live. > > > > > > To resolve this, while not re-introducing the issues 3bdf878 > > > (flickering as the PWM got reset while in a PWM cycle). Only force > > > an update of the settings when at 100% duty, which shouldn't have a > > > noticeable effect on the output but is enough to ensure the > > > behaviour is as expected on disable. > > > > > > Signed-off-by: Sjoerd Simons <sjoerd.simons@xxxxxxxxxxxxxxx> > > > --- > > > Changes since v1: > > > Fix small issues pointed out by Tomasz Figa > > > - Correct various coding style issues > > > - Read the current value of the tcmp register for comparison > > > rather then using a non-trivial comparison to decide whether the > > > current state was 100% duty > > > - Move the code to force manual update out into its own function > > > - Clarify the comment indicating why a manual update is sometimes > > > required > > > > > > drivers/pwm/pwm-samsung.c | 31 ++++++++++++++++++++++++++++++- > > > 1 file changed, 30 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c > > > index 3e9b583..649f6c4 100644 > > > --- a/drivers/pwm/pwm-samsung.c > > > +++ b/drivers/pwm/pwm-samsung.c > > > @@ -269,12 +269,31 @@ static void pwm_samsung_disable(struct > > > pwm_chip *chip, struct pwm_device *pwm) > > > spin_unlock_irqrestore(&samsung_pwm_lock, flags); } > > > > > > +static void pwm_samsung_manual_update(struct samsung_pwm_chip > > > *chip, > > > + struct pwm_device *pwm) > > > +{ > > > + unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm); > > > + u32 tcon; > > > + unsigned long flags; > > > + > > > + spin_lock_irqsave(&samsung_pwm_lock, flags); > > > + > > > + tcon = readl(chip->base + REG_TCON); > > > + tcon |= TCON_MANUALUPDATE(tcon_chan); > > > + writel(tcon, chip->base + REG_TCON); > > > + > > > + tcon &= ~TCON_MANUALUPDATE(tcon_chan); > > > + writel(tcon, chip->base + REG_TCON); > > > + > > > + spin_unlock_irqrestore(&samsung_pwm_lock, flags); > > > +} > > > + > > > static int pwm_samsung_config(struct pwm_chip *chip, struct > > > pwm_device *pwm, int duty_ns, int period_ns) > > > { > > > struct samsung_pwm_chip *our_chip = > > > to_samsung_pwm_chip(chip); struct samsung_pwm_channel *chan = > > > pwm_get_chip_data(pwm); > > > - u32 tin_ns = chan->tin_ns, tcnt, tcmp; > > > + u32 tin_ns = chan->tin_ns, tcnt, tcmp, oldtcmp; > > > > > > /* > > > * We currently avoid using 64bit arithmetic by using the > > > @@ -288,6 +307,7 @@ static int pwm_samsung_config(struct pwm_chip > > > *chip, struct pwm_device *pwm, return 0; > > > > > > tcnt = readl(our_chip->base + REG_TCNTB(pwm->hwpwm)); > > > + oldtcmp = readl(our_chip->base + REG_TCMPB(pwm->hwpwm)); > > > > > > /* We need tick count for calculation, not last tick. */ > > > ++tcnt; > > > @@ -335,6 +355,15 @@ static int pwm_samsung_config(struct pwm_chip > > > *chip, struct pwm_device *pwm, writel(tcnt, our_chip->base + > > > REG_TCNTB(pwm->hwpwm)); writel(tcmp, our_chip->base + > > > REG_TCMPB(pwm->hwpwm)); > > > + /* In case the PWM is currently at 100% duty, force a > > > manual update > > > + * to prevent the signal staying high in the pwm is > > > disabled shortly > > > + * afer this update (before it autoreloaded the new > > > values) . > > > + */ > > > + if (oldtcmp == (u32) -1) { > > > + dev_dbg(our_chip->chip.dev, "Forcing manual > > > update"); > > > + pwm_samsung_manual_update(our_chip, pwm); > > > + } > > > + > > > chan->period_ns = period_ns; > > > chan->tin_ns = tin_ns; > > > chan->duty_ns = duty_ns; > > > > > > > -- Sjoerd Simons <sjoerd.simons@xxxxxxxxxxxxxxx> Collabora Ltd. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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