linux-kernel - Re: [PATCH 1/5] dt-bindings: arm: mediatek: mmsys: change compatible for MT8195

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Message-ID: <a8e18b62-f49f-7c99-e046-3ee609e11627@gmail.com>
Date:   Thu, 15 Sep 2022 18:20:28 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Jason-JH Lin <jason-jh.lin@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     CK Hu <ck.hu@...iatek.com>, Rex-BC Chen <rex-bc.chen@...iatek.com>,
        Singo Chang <singo.chang@...iatek.com>,
        Nancy Lin <nancy.lin@...iatek.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH 1/5] dt-bindings: arm: mediatek: mmsys: change compatible
 for MT8195

Hi Jason,

On 15/09/2022 03:24, Jason-JH Lin wrote:
> Hi Matthias,
> 
> Thanks for the reviews.
> 
> On Wed, 2022-09-14 at 23:24 +0200, Matthias Brugger wrote:
>>
>> On 14/09/2022 20:23, Jason-JH.Lin wrote:
>>> For previous MediaTek SoCs, such as MT8173, there are 2 display HW
>>> pipelines binding to 1 mmsys with the same power domain, the same
>>> clock driver and the same mediatek-drm driver.
>>>
>>> For MT8195, VDOSYS0 and VDOSYS1 are 2 display HW pipelines binding
>>> to
>>> 2 different power domains, different clock drivers and different
>>> mediatek-drm drivers.
>>>
>>> Moreover, Hardware pipeline of VDOSYS0 has these components: COLOR,
>>> CCORR, AAL, GAMMA, DITHER. They are related to the PQ (Picture
>>> Quality)
>>> and they makes VDOSYS0 supports PQ function while they are not
>>> including in VDOSYS1.
>>>
>>> Hardware pipeline of VDOSYS1 has the component ETHDR (HDR related
>>> component). It makes VDOSYS1 supports the HDR function while it's
>>> not
>>> including in VDOSYS0.
>>>
>>> To summarize0:
>>> Only VDOSYS0 can support PQ adjustment.
>>> Only VDOSYS1 can support HDR adjustment.
>>>
>>> Therefore, we need to separate these two different mmsys hardwares
>>> to
>>> 2 different compatibles for MT8195.
>>>
>>> Fixes: 81c5a41d10b9 ("dt-bindings: arm: mediatek: mmsys: add mt8195
>>> SoC binding")
>>> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
>>> Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
>>> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>
>> I'm not sure Krzysztof gave his Acked-by tag.
> 
> I'll remove this tag.
>>
>>> ---
>>>    .../devicetree/bindings/arm/mediatek/mediatek,mmsys.yaml        |
>>> 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.yam
>>> l
>>> b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.yam
>>> l
>>> index 6ad023eec193..a53b32c0a608 100644
>>> ---
>>> a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.yam
>>> l
>>> +++
>>> b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.yam
>>> l
>>> @@ -32,6 +32,8 @@ properties:
>>>                  - mediatek,mt8186-mmsys
>>>                  - mediatek,mt8192-mmsys
>>>                  - mediatek,mt8195-mmsys
>>> +              - mediatek,mt8195-vdosys0
>>
>> As I said in the last submission, we should make mediatek,mt8195-
>> mmsys as a
>> fallback of vdosys0. Actually mediatek,mt8195-mmsys is only used for
>> the
>> fallback of vdosys0.
> 
> I think adding both vdosys0 and vdosys1 can make the description of
> this patch clearer.
> 
> It's find to me to only add "mediatek,mt8195-vdosys0" in this patch.
> So I'll remove the "mediatek,mt8195-vdosys1" at the next version.
> 

That's not what I wanted to suggest. Up to now in upstream kernel compatible 
mediatek,mt8195-mmsys enables support fro vdosys0. The vdosys1 is not yet 
upstream, so no support.
If we change the compatible, we should keep mediatek,mt8195-mmsys as fallback of 
"mediatek,mt8195-vdosys0" so that older device tree blobs won't break with a 
newer kernel.
For "mediatek,mt8195-vdosys1" we do not need a fallback compatible as the code 
never reached upstream, so no breakage expected.

Hope I explain myself now.

Regards,
Matthias


> Regards,
> Jason-JH.Lin
>>
>> Regards,
>> Matthias
>>
>>> +              - mediatek,mt8195-vdosys1
>>>                  - mediatek,mt8365-mmsys
>>>              - const: syscon
>>>          - items:
>>
>>