linux-kernel - Re: [RFC 3/5] dt-bindings: power: Add binding for MediaTek MT7988 topmisc power controller

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Message-ID: <95b965c2-1f03-423b-86a1-cd22784b480d@collabora.com>
Date: Tue, 15 Apr 2025 16:12:54 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: frank-w@...lic-files.de, Frank Wunderlich <linux@...web.de>,
 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>
Cc: Daniel Golle <daniel@...rotopia.org>, Sam Shih <sam.shih@...iatek.com>,
 MandyJH Liu <mandyjh.liu@...iatek.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
Subject: Re: [RFC 3/5] dt-bindings: power: Add binding for MediaTek MT7988
 topmisc power controller

Il 15/04/25 16:03, Frank Wunderlich ha scritto:
> Am 15. April 2025 11:59:06 MESZ schrieb AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>:
>> Il 15/04/25 11:52, Frank Wunderlich ha scritto:
>>> Hi Angelo,
>>>
>>> Am 14. April 2025 12:25:23 MESZ schrieb AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>:
>>>> Il 13/04/25 10:58, Frank Wunderlich ha scritto:
>>>>> From: Frank Wunderlich <frank-w@...lic-files.de>
>>>>>
>>>>> Topmisc is a systemcontroller used for xs-phy and ethernet on  mt7988.
>>>>> Add binding for it.
>>>>
>>>> That's the wrong binding... check mfd/syscon.yaml :-)
>>>>
>>>> P.S.: Is there any reset controller in topmisc? Any clock?
>>>>        If yes, syscon.yaml is also wrong, and you need a driver for that.
>>>>        Remember: If it turns out *later* that this has clk/resets and the
>>>>        bindings are already set for just a syscon, it's gonna be way harder!
>>>>
>>>> Cheers,
>>>> Angelo
>>>
>>> Ok based on the power-domain-cells property i guessed powercontroller is the right place.
>>
>> power-domain-cells, but without any power domain assignment, so that was wrong :)))
>>
>>>
>>> But based on your suggestion i tried moving compatible to syscon binding and made dtbs_check here.
>>>
>>> I can confirm dropping the unexpected properties reported by syscon binding (power-domain-cells,clock-cells,adress-cells and size-cells) are not needed for function (xsphy and ethernet).
>>>
>>> For verifying that there are really no clocks/resets in topmisc (have not found it in public available register documents) i asked mtk (waiting for answer).
>>>
>>> Also got it working without the syscon compatible by changing ethernet driver too (after this change xsphy was also working).
>>
>> Perfect, a bit of a cleanup and you're done, then!
>>
>> Cheers!
>>
>>>
>>> Eth:
>>> https://github.com/frank-w/BPI-Router-Linux/commit/d866e648717800b6f6395ad36c38f9effcf0498d
>>> Xsphy:
>>> <https://github.com/frank-w/BPI-Router-Linux/commit/0121a94df99700487704ca056b210b13db07e90c>
>>>
>>> regards Frank
>>
>>
>>
> 
> Got response from MTK and basicly topmisc contains a powercontroller (for cpu and internal 2g5) but currently not needed because ATF already switch this on. The second part is the pcs/phy muxing and 3rd some unneeded switches (where i have no detailed information). But no clocks or resets as these are handled in the connected platform driver (xsphy/ethernet).
> 
> So my original binding imho made more sense.
> 
> The syscon binding seems to need syscon fallback and shows error about unexpected "compatible" property. The binding itself does not contain any properties but references syscon-common where iiuc compatible property must have at least 2 items and requires the "syscon" fallback.
> 
> Mtk suggests splitting topmisc into the 2 blocks by only using the mux part as syscon with splitting the reg. If powerdomain really is needed then a second topmisc node could be added and bound to a new driver.
> 

I agree with MediaTek's suggestion. Split it, that just makes more sense.

Besides, if the first part (the power controller in topmisc) is managed by ATF it's
a good idea to avoid touching anything in there from the kernel :-)


> But this would need a bit more of testing.
> regards Frank