linux-kernel - Re: [PATCH v1 1/2] dt-bindings: phy: mtk-tphy: add property for software role switch

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Message-ID: <df9a09a5-15eb-4760-b312-d54e4e57283c@kernel.org>
Date: Sun, 24 Aug 2025 10:18:16 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Arseniy Velikanov <me@...merle.pw>
Cc: Chunfeng Yun <chunfeng.yun@...iatek.com>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v1 1/2] dt-bindings: phy: mtk-tphy: add property for
 software role switch

On 24/08/2025 08:25, Arseniy Velikanov wrote:
> On 15.08.2025 10:28, Krzysztof Kozlowski wrote:
>> On Fri, Aug 15, 2025 at 03:48:24AM +0400, Arseniy Velikanov wrote:
>>> Add a boolean property to enable software control of the PHY mode
>>> switching.
>>>
>>> Signed-off-by: Arseniy Velikanov <me@...merle.pw>
>>> ---
>>>   Documentation/devicetree/bindings/phy/mediatek,tphy.yaml | 6 ++++++
>>>   1 file changed, 6 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml b/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
>>> index b2218c151939..a90890d4a86f 100644
>>> --- a/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
>>> +++ b/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
>>> @@ -255,6 +255,12 @@ patternProperties:
>>>             use the property "mediatek,syscon-type" for newer SoCs that support it.
>>>           type: boolean
>>>   
>>> +      mediatek,software-role-switch:
>>
>> No, bindings do not describe software.
> Sorry, I didn't quite understand you.
> 
> With this property the driver changes phy mode manually using debug regs 


Here is the problem:     ^^^^^^^^, driver.

> instead of configuring hardware mode switching (because it's broken on 
> some platforms). So every time the role in usb-role-switch changes, it 
> has to switch phy mode. That's what I mean by "software".
> 
> I can rename this property to `mediatek,force-mode-switch` if that's a 
> issue.


Describe the hardware problem, characteristic, wiring or whatever else,
but not the drivers and not software.

force-media-switch is the same uninformative and same underlying
instruction for the driver.

Best regards,
Krzysztof