linux-kernel - Re: [PATCH 2/8] dt-bindings: display: bridge: thc63lvd1024: Add lvds map property

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Message-ID: <20180423073504.GN4235@w540>
Date:   Mon, 23 Apr 2018 09:35:04 +0200
From:   jacopo mondi <jacopo@...ndi.org>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Jacopo Mondi <jacopo+renesas@...ndi.org>, architt@...eaurora.org,
        a.hajda@...sung.com, Laurent.pinchart@...asonboard.com,
        airlied@...ux.ie, daniel@...ll.ch,
        linux-renesas-soc@...r.kernel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] dt-bindings: display: bridge: thc63lvd1024: Add lvds
 map property

Hi Peter,
   thanks for commenting,

On Sun, Apr 22, 2018 at 10:02:41PM +0200, Peter Rosin wrote:
> On 2018-04-19 11:31, Jacopo Mondi wrote:
> > The THC63LVD1024 LVDS to RGB bridge supports two different input mapping
> > modes, selectable by means of an external pin.
> >
> > Describe the LVDS mode map through a newly defined mandatory property in
> > device tree bindings.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > ---
> >  .../devicetree/bindings/display/bridge/thine,thc63lvd1024.txt          | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt b/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> > index 37f0c04..0937595 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> > +++ b/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> > @@ -12,6 +12,8 @@ Required properties:
> >  - compatible: Shall be "thine,thc63lvd1024"
> >  - vcc-supply: Power supply for TTL output, TTL CLOCKOUT signal, LVDS input,
> >    PPL and digital circuitry
> > +- thine,map: LVDS mapping mode selection signal, pin name "MAP". Shall be <1>
> > +  for mapping mode 1, <0> for mapping mode 2
>
> Since the MAP pin is an input pin, I would expect there to be an optional gpio
> specifier like thine,map-gpios so that the driver can set it according to
> the value given in thine,map in case the HW has a line from some gpio output
> to the MAP pin (instead of hardwired hi/low which seem to be your thinking).

I see... As the only use case I had has the pin tied to vcc, I
thought about making it a binary property, and I wonder in how many
cases the chip 'MAP' pin would actually be GPIO controlled input and
not an hardwired one instead. I don't see the LVDS mapping mode to be
changed at runtime, but you are right, who knows....

Do you think we can add an options 'thine,map-gpios' property along
to the proposed ones?

thanks
   j

>
> Cheers,
> Peter
>
> >
> >  Optional properties:
> >  - powerdown-gpios: Power down GPIO signal, pin name "/PDWN". Active low
> > @@ -36,6 +38,7 @@ Example:
> >
> >  		vcc-supply = <&reg_lvds_vcc>;
> >  		powerdown-gpios = <&gpio4 15 GPIO_ACTIVE_LOW>;
> > +		thine,map = <1>;
> >
> >  		ports {
> >  			#address-cells = <1>;
> >
>

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