* Hans Verkuil <hverkuil@xxxxxxxxx> [190325 15:52]: > Hi Tony, > > 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. OK > 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. OK > 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. Hmm I wonder if we could test for HPD floating and then disable cec? Then we would know nothing is connected, right? > 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? >From distro kernel point of view we should find some way to disable cec dynamically. Can we maybe do something via /sys or some command line option for cec.ko? Then if we find a way to check for floating HPD pin or something we could support that too. Regards, Tony
