linux-kernel - Re: [PATCH 01/12] dt-bindings: display: sprd: adapt for UMS9230 support

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Message-ID: <40fd4502-71d5-435e-83f2-2df933c0467b@kernel.org>
Date: Sun, 20 Jul 2025 17:38:02 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Otto Pflüger <otto.pflueger@...cue.de>
Cc: David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Orson Zhai <orsonzhai@...il.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Chunyan Zhang <zhang.lyra@...il.com>, Kevin Tang <kevin.tang@...soc.com>,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/12] dt-bindings: display: sprd: adapt for UMS9230
 support

On 20/07/2025 15:55, Otto Pflüger wrote:
>>>  
>>>    clock-names:
>>> -    items:
>>> -      - const: clk_src_96m
>>> +    oneOf:
>>> +      - items:
>>> +          - const: clk_src_96m
>>> +      - items:
>>> +          - const: enable
>>
>> Why this is completely different clock? How same class device could have
>> completely different clock INPUT?
> 
> The clocks should be the same on sharkl3 (sc9863a) and ums9230, but
> the existing bindings don't really make sense here or are incomplete.
> AFAIK there is no SoC in which this display controller is directly
> connected to the PLL as shown in the example. The DSI controller is

This is not the PLL. Gate either. You are looking from wrong side - how
clock is generated.

You describe here CLOCK INPUT.

> connected to a clock gate. The DPU actually does have two clocks, both
> of which are clock muxes that allow selecting different frequencies and
> one of which is behind a clock gate. I can add the second clock for the
> DPU if needed.
> 
> Since nothing seems to be using these bindings at the moment, would it
> be okay to drop the old clock names that refer to specific frequencies?

It is still completely irrelevant whether these are muxes. Dropping
existing properties is ABI change, but anyway first figure out what is
here really.

Best regards,
Krzysztof