linux-kernel - Re: [PATCH 2/4] dt-bindings: display: panel: Add Himax HX83112B

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Message-ID: <ad132ebd-92f2-428c-95c2-d1986b5d060f@lucaweiss.eu>
Date: Sat, 29 Mar 2025 14:54:27 +0100
From: Luca Weiss <luca@...aweiss.eu>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Jessica Zhang <quic_jesszhan@...cinc.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/4] dt-bindings: display: panel: Add Himax HX83112B

Hi all,

On 2/24/25 9:16 AM, Krzysztof Kozlowski wrote:
> On 23/02/2025 16:29, Luca Weiss wrote:
>> Hi Krzysztof,
>>
>> On 23-02-2025 12:54 p.m., Krzysztof Kozlowski wrote:
>>> On Sat, Feb 22, 2025 at 06:58:05PM +0100, Luca Weiss wrote:
>>>> Himax HX83112B is a display driver IC used to drive LCD DSI panels.
>>>> Describe it and the Fairphone 3 panel from DJN using it.
>>>>
>>>> Signed-off-by: Luca Weiss <luca@...aweiss.eu>
>>>> ---
>>>>    .../bindings/display/panel/himax,hx83112b.yaml     | 75 ++++++++++++++++++++++
>>>>    1 file changed, 75 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/display/panel/himax,hx83112b.yaml b/Documentation/devicetree/bindings/display/panel/himax,hx83112b.yaml
>>>> new file mode 100644
>>>> index 0000000000000000000000000000000000000000..e6bd4b33d40be98e479d84617aea6d2af0df70e4
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/display/panel/himax,hx83112b.yaml
>>>> @@ -0,0 +1,75 @@
>>>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/display/panel/himax,hx83112b.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: Himax HX83112B-based DSI display panels
>>>> +
>>>> +maintainers:
>>>> +  - Luca Weiss <luca@...aweiss.eu>
>>>> +
>>>> +description:
>>>> +  The Himax HX83112B is a generic DSI Panel IC used to control
>>>> +  LCD panels.
>>>> +
>>>> +allOf:
>>>> +  - $ref: panel-common.yaml#
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    contains:
>>>> +      const: djn,fairphone-fp3-panel
>>>
>>> Why no himax,hx83112b fallback?
>>
>> While this is the driver IC for this panel, I don't think there's any
>> "generic" init sequence that can successfully configure this panel, so
>> generic hx83112b driver could work I'd say.
> 
> 
> Hm, indeed usually this would mean no need for unusable fallback alone,
> but still drivers could use it for some common pieces of code. I imagine
> there could be a piece of init sequence which is generic. Or some piece
> of attributes.
> We already have examples of both approaches for panels - with generic
> fallback (himax,hx83102) and without (himax,hx83112a).
> 
> @Rob
> what is your generic advice? Which of above (himax,hx83102 vs
> himax,hx83112a) should be used, if the fallback compatible cannot be
> used alone?

I believe this thread is still pending of a resolution, based on the 
model number I've found, I made the compatible "djn,98-03057-6598b-i" 
for v2, but it's still a question whether himax,hx83112b should be part 
of the compatible.

Regards
Luca

> 
> Best regards,
> Krzysztof