[PATCHv2 7/7] drm/omap: hdmi4: fix use of uninitialized var

[Tony Lindgren]

* Tomi Valkeinen <tomi.valkeinen at ti.com> [191010 06:48]:
> On 08/10/2019 17:21, Tony Lindgren wrote:
> > * Tomi Valkeinen <tomi.valkeinen at ti.com> [191008 14:17]:
> > > On 08/10/2019 17:13, Tony Lindgren wrote:
> > > > * Tomi Valkeinen <tomi.valkeinen at ti.com> [190930 10:38]:
> > > > > If use_mclk is false, mclk_mode is written to a register without
> > > > > initialization. This doesn't cause any ill effects as the written value
> > > > > is not used when use_mclk is false.
> > > > > 
> > > > > To fix this, write use_mclk only when use_mclk is true.
> > > > 
> > > > Hey nice catch. Based on a quick test looks like this fixes an
> > > > issue where power consumption stays higher after using HDMI.
> > > > 
> > > > Would be nice to have merged in the v5.4-rc series:
> > > > 
> > > > Tested-by: Tony Lindgren <tony at atomide.com>
> > > 
> > > Really? Ok, well, then it was a good random find =).
> > 
> > Yeah so it seems :) Earlier I thought there's still some
> > clkctrl setting wrong after using HDMI, but did not see
> > anything diffing the clkctrl registers before and after
> > and gave up.
> > 
> > > I did already push this to drm-misc-next, as I thought it does not have any
> > > real effect. I'll check if it's ok to push to drm-misc-fixes too, with Cc
> > > stable.
> > 
> > OK great thanks.
> 
> Pushing this to fixes too would cause conflicts, so we shouldn't push
> without good reason. How much power saving you see?

Sure no rush with this one. I should also test again that it
really fixes the issue I'm seeing.

Hmm so what register does this clock actually change?

I'm seeing an increase of few tens of extra mW, which means at
least one day of standby time less for me :) It does not happen
always, maybe half of the time.

> I think this can still be sent to stable later, after it has been merged to
> mainline.

Yes sure.

Thanks,

Tony