Hi Hans, On 03/04/2018 10:27, Hans Verkuil wrote: > On 27/03/18 00:25, Rob Herring wrote: >> On Fri, Mar 23, 2018 at 01:59:13PM +0100, Hans Verkuil wrote: >>> From: Hans Verkuil <hans.verkuil@xxxxxxxxx> >>> >>> Some boards have both a DesignWare and their own CEC controller. >>> The CEC pin is only hooked up to their own CEC controller and not >>> to the DW controller. >>> >>> Add the cec-disable property to disable the DW CEC controller. >>> >>> This particular situation happens on Amlogic boards that have their >>> own meson CEC controller. >> >> Seems like we could avoid this by describing how the CEC line is hooked >> up which could be needed for other reasons. > > So there are three situations: > > 1) The cec pin is connected to the DW HDMI TX. That's already supported. > 2) The cec pin is not connected at all, but the CEC IP is instantiated. > We need the cec-disable property for that. This simply states that the > CEC pin is not connected. > 3) The cec pin is connected to an HDMI RX. We do not support this at the > moment. If we want to support this, then we need a 'hdmi-rx' phandle > that points to the HDMI receiver that the CEC pin is associated with. > This will be similar to the already existing 'hdmi-phandle' property > used to associate a CEC driver with an HDMI transmitter. In hindsight > it would have been better if 'hdmi-phandle' was named 'hdmi-tx' :-( > > I can make a binding proposal for 3, but I have no hardware to test it, > so I think it is better to add this only when someone has hardware. It > will require quite a few changes to the driver and likely also the CEC core. Can't we simply add a property to override the HW config fields in this case ? It will be then usable with any feature the is enabled by reading the config bits like AHB Audio, I2c, CEC, ... and maybe many more in the future. Neil > > Regards, > > Hans > >> >>> >>> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> >>> Acked-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx> >>> --- >>> Documentation/devicetree/bindings/display/bridge/dw_hdmi.txt | 3 +++ >>> 1 file changed, 3 insertions(+) >
