linux-kernel - Re: [PATCH 2/4] arm64: dts: mediatek: mt8365: use a specific SCPSYS compatible

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Date: Tue, 21 May 2024 19:28:20 +0200
From: Alexandre Mergnat <amergnat@...libre.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Lee Jones <lee@...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>,
 MandyJH Liu <mandyjh.liu@...iatek.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/4] arm64: dts: mediatek: mt8365: use a specific SCPSYS
 compatible



On 21/05/2024 16:13, AngeloGioacchino Del Regno wrote:
> Il 21/05/24 15:26, Alexandre Mergnat ha scritto:
>>
>>
>> On 21/05/2024 10:22, Krzysztof Kozlowski wrote:
>>> On 20/05/2024 17:23, Alexandre Mergnat wrote:
>>>> Hello Krzysztof,
>>>>
>>>> On 20/05/2024 12:12, AngeloGioacchino Del Regno wrote:
>>>>> Il 20/05/24 12:03, Krzysztof Kozlowski ha scritto:
>>>>>> On 20/05/2024 11:55, AngeloGioacchino Del Regno wrote:
>>>>>>> Il 18/05/24 23:11, Krzysztof Kozlowski ha scritto:
>>>>>>>> SoCs should use dedicated compatibles for each of their syscon nodes to
>>>>>>>> precisely describe the block.  Using an incorrect compatible does not
>>>>>>>> allow to properly match/validate children of the syscon device.  Replace
>>>>>>>> SYSCFG compatible, which does not have children, with a new dedicated
>>>>>>>> one for SCPSYS block.
>>>>>>>>
>>>>>>>> Signed-off-by: Krzysztof Kozlowski<krzysztof.kozlowski@...aro.org>
>>>>>>> Technically, that's not a SCPSYS block, but called SYSCFG in MT8365, but the
>>>>>>> meaning and the functioning is the same, so it's fine for me.
>>>>>> So there are two syscfg blocks? With exactly the same set of registers
>>>>>> or different?
>>>>>>
>>>>> I'm not sure about that, I don't have the MT8365 datasheet...
>>>>>
>>>>> Adding Alexandre to the loop - I think he can clarify as he should have the
>>>>> required documentation.
>>>> Unfortunately, The SCPSYS (@10006000) isn't documented, but according to the functionnal
>>>> specification, it seems to have only one block.
>>>>
>>>> I don't have the history why SYSCFG instead of SCPSYS.
>>>>
>>>> I've tested your serie and have a regression at the kernel boot time:
>>>> [    7.738117] mtk-power-controller 10006000.syscon:power-controller: Failed to create device link
>>>> (0x180) with 14000000.syscon
>>>>
>>>> It's related to your patch 3/4.
>>> I don't see how this could be related. The error is mentioning entirely
>>> different node - mmsys. No driver binds to 10006000.syscon, except the
>>> MFD syscon of course, so my change should have zero effect on drivers.
>>>
>>> The mtk-pm-domains (so child of patch affected in 3/4) only takes regmap
>>> from the parent, so the cells again are not related.
>>>
>>> Just to be sure: you are testing mainline or next, without any other
>>> patches on top except mine?
>>
>> I've tested on next
>>
>> * a018995ac19c (HEAD -> temp, me/temp) arm64: dts: mediatek: mt8173-elm: correct PMIC's syscon reg 
>> entry
>> * 0f118436c61c arm64: dts: mediatek: mt8365: drop incorrect power-domain-cells
>> * d40e424fe6dc arm64: dts: mediatek: mt8365: use a specific SCPSYS compatible
>> * d7caa08a4a9b dt-bindings: mfd: mediatek,mt8195-scpsys: add mediatek,mt8365-scpsys
>> * 82d92a9a1b9e (tag: next-20240515, linux-next/master) Add linux-next specific files for 20240515
>> *   77ba09d6e7cb Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux.git
>> |\
>> | * dedcf3a8e704 tools/power turbostat: version 2024.05.10
>> | * baac2f4c7f3b tools/power turbostat: Ignore pkg_cstate_limit when it is not available
>> | * a0525800e2dc tools/power turbostat: Fix order of strings in pkg_cstate_limit_strings
>> | * ffc2e3d90e6f tools/power turbostat: Read Package-cstates via perf
>>
>>
>> I did the test with and without "0f118436c61c arm64: dts: mediatek: mt8365: drop incorrect 
>> power-domain-cells"
>>
>> Without this specific patch, no regression.
>>
>>
> 
> Honestly, that makes very little sense to me - that property is useless and it's
> like it's never been there... at least, no MTK driver is parsing that and there's
> definitely no power domain in the top node (a child does, but not the parent).
> 
> Is this a flaky result? Did you actually try to reboot multiple times to check if
> the platform is *really broken* after that commit?
> 
> Sorry, it's not mistrust or anything, but I've been in this situation multiple
> times in the past, usually always on linux-next (because it's constantly broken :P)

MMMmm you're right, I can't reproduce this time...
Sorry for the noise.

Reviewed-by: Alexandre Mergnat <amergnat@...libre.com>
Tested-by: Alexandre Mergnat <amergnat@...libre.com>

-- 
Regards,
Alexandre