CEC blocks idle on omap4

[Tony Lindgren]

* Hans Verkuil <hverkuil at xs4all.nl> [190325 16:12]:
> On 3/25/19 4:55 PM, Laurent Pinchart wrote:
> >> The reality is that HDMI CEC and HDMI video are really independent of
> >> one another. So I wonder if it isn't better to explain the downsides
> >> of enabling CEC for the omap4 in the CONFIG_OMAP4_DSS_HDMI_CEC
> >> description. And perhaps disable it by default?
> > 
> > This should be controllable by userspace. From a product point of view,
> > it should be possible to put the system in a deep sleep state where CEC
> > isn't available, or in a low sleep state where CEC works as expected.
> > 
> 
> Userspace can always disable CEC. The hdmi_cec_adap_enable() callback in
> hdmi4_cec.c is called whenever the CEC adapter is enabled or disabled.

OK

> I'm not actually sure why hdmi4_cec_init() would block anything since it
> just registers the CEC device. It does not enable it until userspace
> explicitly enables it with e.g. 'cec-ctl --playback'.
> 
> hdmi4_cec_init() does configure a CEC clock, but that can be moved to
> hdmi_cec_adap_enable() if necessary.

Hey I'm pretty sure that's the right fix then :)

> Note that I am not sure what is meant with 'SoC core retention idle',
> so perhaps I just misunderstand the problem.

If certain SoC clocks are busy, the SoC will not enter deeper
idle states. The hardware has autoidle type features on omaps.

Regards,

Tony