[PATCHv2 1/3] dt-bindings: display: dw_hdmi.txt: add cec-disable property

[narmstrong@baylibre.com (Neil Armstrong)]

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@cisco.com>
>>>
>>> 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@cisco.com>
>>> Acked-by: Neil Armstrong <narmstrong@baylibre.com>
>>> ---
>>>  Documentation/devicetree/bindings/display/bridge/dw_hdmi.txt | 3 +++
>>>  1 file changed, 3 insertions(+)
>