Re: [PATCH RESEND 3/4] dt-bindings: drm/bridge: analogix-anx78xx: support bypass GPIO

From: Hsin-Yi Wang
Date: Mon Dec 09 2019 - 10:10:03 EST

On Mon, Dec 9, 2019 at 10:55 PM Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
> Hi Hsin-Yi,
> Thank you for the patch.
> On Mon, Dec 09, 2019 at 10:50:15PM +0800, Hsin-Yi Wang wrote:
> > Support optional feature: bypass GPIO.
> >
> > Some SoC (eg. mt8173) have a hardware mux that connects to 2 ports:
> > anx7688 and hdmi. When the GPIO is active, the bridge is bypassed.
> This doesn't look like the right place to fix this, as the mux is
> unrelated to the bridge. You would have to duplicate this logic in every
> bridge driver otherwise.
> Could you describe the hardware topology in a bit more details ? I can
> then try to advise on how to best support it.
Hi Laurent,

The mt8173 layout is:

MT8173 HDMI bridge-- hardware mux --- HDMI
------------ anx7688
There's a hardware mux that takes mt8173 hdmi as input and has 2
output port: native hdmi and anx7688 bridge.
If gpio is active, we would like it to go to HDMI.

Previous approach is to make hardware mux a generic gpio mux bridge,
but this is probably a very rare use case that is only for
We merge the mux and anx7688 to a single bridge and leave this as an
optional feature in this time.