linux-kernel - Re: [PATCH 2/2] dt-bindings: display: bridge: lt8912b: document 'lontium,pn-swap' property

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAH3L5QooAXDYAxOdMkPrW1mx04ZgTv_kMU5VSAby9J3Hb_RFOg@mail.gmail.com>
Date: Wed, 3 Apr 2024 09:16:31 +0300
From: Alexandru Ardelean <alex@...uggie.ro>
To: Conor Dooley <conor@...nel.org>
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, adrien.grassein@...il.com, 
	andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, 
	airlied@...il.com, daniel@...ll.ch, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, tzimmermann@...e.de, robh@...nel.org, 
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, 
	stefan.eichenberger@...adex.com, francesco.dolcini@...adex.com, 
	marius.muresan@....ro, irina.muresan@....ro
Subject: Re: [PATCH 2/2] dt-bindings: display: bridge: lt8912b: document
 'lontium,pn-swap' property

On Tue, Apr 2, 2024 at 9:06 PM Conor Dooley <conor@...nel.org> wrote:
>
> On Tue, Apr 02, 2024 at 01:59:25PM +0300, Alexandru Ardelean wrote:
> > On some HW designs, it's easier for the layout if the P/N pins are swapped.
> > The driver currently has a DT property to do that.
>
> "currently", because 1/2 adds it. bindings patches should precede the
> driver patches in the series, so please swap the patches and remove this
> portion of the description.

ack;
i'll invert the order and remove this;

>
> >
> > This change documents the 'lontium,pn-swap' property.
> >
> > Signed-off-by: Alexandru Ardelean <alex@...uggie.ro>
> > ---
> >  .../devicetree/bindings/display/bridge/lontium,lt8912b.yaml | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > index 2cef252157985..3a804926b288a 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > +++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > @@ -24,6 +24,12 @@ properties:
> >      maxItems: 1
> >      description: GPIO connected to active high RESET pin.
> >
> > +  lontium,pn-swap:
> > +    description: Swap the polarities of the P/N pins in software.
> > +      On some HW designs, the layout is simplified if the P/N pins
> > +      are inverted.
>
> Please explain what configuration of a board would cause these to be
> swapped, rather than why someone might want to configure the board this
> way. I've got no idea what this hardware is actually doing, so this is
> being pulled out of a hat, but I'd expect something like "Some boards
> swap the polarity of the P/N pins, use this property to indicate this to
> software".

ack
if it's fine with you, i'll use your suggested description;

for a broader context, we were using a DSI-HDMI converter [1] from
SomLabs on a different (than SomLabs) board;
and we were not seeing anything on the HDMI-connected display;
as I understand it, some DSI-HDMI bridges support P/N auto-inversion;
this one doesn't AFAICT;
on this DSI-HDMI converter [1], we've noticed that the P/N pins were
inverted from the DSI to the chip (vs what we expected to see)
after changing the register value (for the P/N swap), it worked;
our conclusion was that, the design of the converter (board) was done
as-such, because it made the layout easier

[1] https://wiki.somlabs.com/index.php/SL-MIPI-LVDS-HDMI-CNV-11_Datasheet_and_Pinout

>
> > +    type: boolean
>
> The type here should be flag.

ack; i'll change the type

>
> Cheers,
> Conor.
>
> > +
> >    ports:
> >      $ref: /schemas/graph.yaml#/properties/ports
> >
> > --
> > 2.44.0
> >