linux-kernel - Re: [PATCH 1/3] dt-bindings: display: bridge: add sam9x7-lvds compatible

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Message-ID: <20240130191255.GA2164257-robh@kernel.org>
Date: Tue, 30 Jan 2024 13:12:55 -0600
From: Rob Herring <robh@...nel.org>
To: Dharma.B@...rochip.com
Cc: conor@...nel.org, krzk@...nel.org, Manikandan.M@...rochip.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,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, Linux4Microchip@...rochip.com
Subject: Re: [PATCH 1/3] dt-bindings: display: bridge: add sam9x7-lvds
 compatible

On Tue, Jan 23, 2024 at 03:39:13AM +0000, Dharma.B@...rochip.com wrote:
> Hi Conor,
> 
> On 22/01/24 10:07 pm, Conor Dooley wrote:
> > On Mon, Jan 22, 2024 at 04:51:16PM +0100, Krzysztof Kozlowski wrote:
> >> On 22/01/2024 09:29, Dharma Balasubiramani wrote:
> >>> Add the 'sam9x7-lvds' compatible binding, which describes the
> >>> Low Voltage Differential Signaling (LVDS) Controller found on Microchip's
> >>> sam9x7 series System-on-Chip (SoC) devices. This binding will be used to
> >>> define the properties and configuration for the LVDS Controller in DT.
> >>>
> >>> Signed-off-by: Dharma Balasubiramani<dharma.b@...rochip.com>
> >>> ---
> >>>   .../display/bridge/microchip,sam9x7-lvds.yaml | 59 +++++++++++++++++++
> >>>   1 file changed, 59 insertions(+)
> >>>   create mode 100644 Documentation/devicetree/bindings/display/bridge/microchip,sam9x7-lvds.yaml
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/display/bridge/microchip,sam9x7-lvds.yaml b/Documentation/devicetree/bindings/display/bridge/microchip,sam9x7-lvds.yaml
> >>> new file mode 100644
> >>> index 000000000000..8c2c5b858c85
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/display/bridge/microchip,sam9x7-lvds.yaml
> >>> @@ -0,0 +1,59 @@
> >>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>> +%YAML 1.2
> >>> +---
> >>> +$id:http://devicetree.org/schemas/display/bridge/microchip,sam9x7-lvds.yaml#
> >>> +$schema:http://devicetree.org/meta-schemas/core.yaml#
> >>> +
> >>> +title: Microchip SAM9X7 LVDS Controller
> >> What is the "X"?
> >>
> >>> +
> >>> +maintainers:
> >>> +  - Dharma Balasubiramani<dharma.b@...rochip.com>
> >>> +
> >>> +description: |
> >> Do not need '|' unless you need to preserve formatting.
> >>
> >>> +  The Low Voltage Differential Signaling Controller (LVDSC) manages data
> >>> +  format conversion from the LCD Controller internal DPI bus to OpenLDI
> >>> +  LVDS output signals. LVDSC functions include bit mapping, balanced mode
> >>> +  management, and serializer.
> >>> +
> >>> +properties:
> >>> +  compatible:
> >>> +    const: microchip,sam9x7-lvds
> >> What is "x"? Wildcard? Then no, don't use it and instead use proper SoC
> >> version number.
> > These SoCs actually do have an x in their name. However, and I do always
> > get confused here, the sam9x7 is a series of SoCs (the cover letter does
> > say this) rather than a specific device.
> > I think the series current consists of a sam9x70 sam9x72 and a sam9x75.
> > The devices are largely similar, but I am not sure if the sam9x70
> > supports LVDS at all. Having a compatible for the series does not seem
> > correct to me.
> Yes, you are correct. Only sam9x72 and sam9x75 have LVDS support, while 
> sam9x70 does not. I will revise the compatibility to include both 
> sam9x72 and sam9x75, as outlined below:
> 
> properties:
>    compatible:
>      enum:
>        - microchip,sam9x72-lvds
>        - microchip,sam9x75-lvds

I would presume these 2 are the same, but the above implies they 
aren't. I think what you had is fine assuming these are all 
fundamentally the same part with just packaging or fused off h/w 
differences.

Rob