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

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Message-ID: <f980706a-2bc7-46f2-8c3e-1cc62a1e2cb7@microchip.com>
Date: Thu, 1 Feb 2024 04:10:39 +0000
From: <Dharma.B@...rochip.com>
To: <robh@...nel.org>
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 31/01/24 12:42 am, Rob Herring wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> 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.

Yes, so is it okay to have compatible for a series? Shall I go ahead with
"
   compatible:
     const: microchip,sam9x7-lvds
"
itself?

-- 
Thanks,
Dharma B.
> 
> Rob