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

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Message-ID: <5047d939-7831-4414-b4f4-94cec78a0446@microchip.com>
Date: Thu, 1 Feb 2024 08:56:45 +0000
From: <Dharma.B@...rochip.com>
To: <krzysztof.kozlowski@...aro.org>, <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 01/02/24 1:09 pm, Krzysztof Kozlowski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 01/02/2024 05:10, Dharma.B@...rochip.com wrote:
>> 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
> 
> You said 9x70, which would match such 9x7 "series", is different, so I
> still think series should not be used. I don't know much about Microchip
> naming scheme, so this x is always confusing. However if these are the
> same, maybe just use sam9x72?

sam9x75 is the first board to be available publicly; hence, I shall use 
the "microchip,sam9x75-lvds" compatible and reuse the same in other 
boards that (features same IP) will come later.

> 
> Best regards,
> Krzysztof
> 

-- 
With Best Regards,
Dharma B.