Hi Hans, On Mon, Mar 25, 2019 at 04:51:57PM +0100, Hans Verkuil wrote: > On 3/25/19 4:32 PM, Tony Lindgren wrote: > > Hi Hans, > > > > Looks like CONFIG_OMAP4_DSS_HDMI_CEC=y blocks SoC core retention > > idle on omap4 if selected. > > > > Should we maybe move hdmi4_cec_init() to hdmi_display_enable() > > and hdmi4_cec_uninit() to hdmi_display_disable()? > > > > Or add some enable/disable calls in addtion to the init and > > uninit calls that can be called from hdmi_display_enable() > > and hdmi_display_disable()? > > For proper HDMI CEC behavior the CEC adapter has to remain active > even if the HPD of the display is low. Some displays pull down the > HPD when in standby, but CEC can still be used to wake them up. > > And we see this more often as regulations for the maximum power > consumption of displays are getting more and more strict. > > So disabling CEC when the display is disabled is not an option. > > Disabling CEC if the source is no longer transmitting isn't a good > idea either since the display will typically still send periodic > CEC commands to the source that it expects to reply to. What's the periodicity of those commands ? Can the system be put to sleep and get woken up when there's CEC activity ? > 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. -- Regards, Laurent Pinchart
