linux-kernel - RE: [PATCH v3 1/8] dt-bindings: display: Add bindings for LVDS bus-timings

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Date:   Fri, 6 Dec 2019 15:10:46 +0000
From:   Fabrizio Castro <fabrizio.castro@...renesas.com>
To:     Rob Herring <robh+dt@...nel.org>
CC:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Simon Horman <horms@...ge.net.au>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        "open list:MEDIA DRIVERS FOR RENESAS - FCP" 
        <linux-renesas-soc@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Sam Ravnborg <sam@...nborg.org>
Subject: RE: [PATCH v3 1/8] dt-bindings: display: Add bindings for LVDS
 bus-timings

Hi Rob,

> From: Rob Herring <robh+dt@...nel.org>
> Sent: 29 August 2019 15:03
> Subject: Re: [PATCH v3 1/8] dt-bindings: display: Add bindings for LVDS bus-timings
> 
> On Wed, Aug 28, 2019 at 1:36 PM Fabrizio Castro
> <fabrizio.castro@...renesas.com> wrote:
> >
> > Dual-LVDS connections need markers in the DT, this patch adds
> > some common documentation to be referenced by both panels and
> > bridges.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
> >
> > ---
> > v2->v3:
> > * new patch
> > ---
> >  .../bindings/display/bus-timings/lvds.yaml         | 38 ++++++++++++++++++++++
> >  1 file changed, 38 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/display/bus-timings/lvds.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/display/bus-timings/lvds.yaml b/Documentation/devicetree/bindings/display/bus-
> timings/lvds.yaml
> > new file mode 100644
> > index 0000000..f35b55a
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/bus-timings/lvds.yaml
> > @@ -0,0 +1,38 @@
> > +# SPDX-License-Identifier: GPL-2.0
> 
> (GPL-2.0-only OR BSD-2-Clause) is preferred for new bindings.
> 
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/display/bus-timings/lvds.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Common Properties for bus timings of LVDS interfaces
> > +
> > +maintainers:
> > +  - Thierry Reding <thierry.reding@...il.com>
> > +  - Fabrizio Castro <fabrizio.castro@...renesas.com>
> > +
> > +description: |
> > +  This document defines device tree properties common to LVDS and dual-LVDS
> > +  interfaces, where a dual-LVDS interface is a dual-link connection with even
> > +  pixels traveling on one connection, and with odd pixels traveling on the other
> > +  connection.
> > +  This document doesn't constitue a device tree binding specification by itself
> 
> typo: constitute
> 
> > +  but is meant to be referenced by device tree bindings.
> > +  When referenced from panel or bridge device tree bindings, the properties
> > +  defined in this document are defined as follows. The panel and bridge device
> > +  tree bindings are responsible for defining whether each property is required
> > +  or optional.
> > +
> > +properties:
> > +  dual-lvds-even-pixels:
> > +    type: boolean
> > +    description:
> > +      This property is specific to an input port of a sink device. When
> 
> The schema should define what nodes these go in. The description seems
> to indicate in 'port' nodes (or endpoint?), but your use in the panel
> binding puts them in the parent.
> 
> > +      specified, it marks the port as recipient of even-pixels.
> > +
> > +  dual-lvds-odd-pixels:
> > +    type: boolean
> > +    description:
> > +      This property is specific to an input port of a sink device. When
> > +      specified, it marks the port as recipient of odd-pixels.
> 
> However, I don't think you even need these. A panel's port numbers are
> fixed can imply even or odd. For example port@0 can be even and port@1
> can be odd. The port numbering is typically panel specific, but we may
> be able to define the numbering generically if we don't already have
> panels with multiple ports.

The ports on the receiving end of the link can be identified by any number,
not necessarily 0 and 1. Since at this point in time we only have 1 use case
for this I'll merge the generic and panel specific dt-schemas together, for
simplicity.
Perhaps we can split them back once we have a second use case?
I'll send a new patch shortly.

Thank you very much for your help and your patience!

Fab

> 
> Also, aren't there dual link DSI panels?
> 
> Rob