linux-kernel - Re: [PATCH v3 3/6] media: dt-bindings: mediatek,vcodec: Remove VDEC

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Message-ID: <a82b7f2d-04d4-4ac0-9a72-ad1c17118e19@notapiano>
Date:   Tue, 20 Jun 2023 08:46:10 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, kernel@...labora.com,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Conor Dooley <conor+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Yunfei Dong <yunfei.dong@...iatek.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3 3/6] media: dt-bindings: mediatek,vcodec: Remove
 VDEC_SYS for mt8183

On Tue, Jun 20, 2023 at 10:12:14AM +0200, Krzysztof Kozlowski wrote:
> On 20/06/2023 02:03, Nícolas F. R. A. Prado wrote:
> > The binding expects the first register space to be VDEC_SYS. But on
> > mt8183, which uses the stateless decoders, this space is used only for
> > controlling clocks and resets, which are better described as separate
> > clock-controller and reset-controller nodes.
> > 
> > In fact, in mt8173's devicetree there are already such separate
> > clock-controller nodes, which cause duplicate addresses between the
> > vdecsys node and the vcodec node. But for this SoC, since the stateful
> > decoder code makes other uses of the VDEC_SYS register space, it's not
> > straightforward to remove it.
> > 
> > In order to avoid the same address conflict to happen on mt8183,
> > since the only current use of the VDEC_SYS register space in
> > the driver is to read the status of a hardware controlled clock, remove
> > the VDEC_SYS register space from the binding and describe an extra
> > syscon that will be used to directly check the hardware status.
> > 
> > Also add reg-names to be able to tell that this new register schema is
> > used, so the driver can keep backward compatibility.
> > 
> > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> > 
> > ---
> > I dropped the tags from this commit since a syscon is now used instead
> > of an extra clock.
> > 
> > Changes in v3:
> > - Removed the active clock
> > - Added a mediatek,vdecsys syscon property
> > 
> > Changes in v2:
> > - Merged with patch 1 (media: dt-bindings: mediatek,vcodec: Allow single
> >   clock for mt8183) to avoid changing number of clocks twice
> > - Added maxItems to reg-names
> > - Constrained clocks for each compatible
> > - Reordered properties for each compatible
> > 
> >  .../media/mediatek,vcodec-decoder.yaml        | 30 +++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml b/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml
> > index 1e56ece44aee..2f625c50bbfe 100644
> > --- a/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml
> > +++ b/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml
> > @@ -21,8 +21,13 @@ properties:
> >        - mediatek,mt8183-vcodec-dec
> >  
> >    reg:
> > +    minItems: 11
> >      maxItems: 12
> >  
> > +  reg-names:
> > +    minItems: 11
> > +    maxItems: 11
> 
> maxItems: 12
> 
> > +
> >    interrupts:
> >      maxItems: 1
> >  
> > @@ -60,6 +65,10 @@ properties:
> >      description:
> >        Describes point to scp.
> >  
> > +  mediatek,vdecsys:
> > +    $ref: /schemas/types.yaml#/definitions/phandle
> > +    description: Phandle to the vdecsys syscon node.
> > +
> >  required:
> >    - compatible
> >    - reg
> > @@ -79,8 +88,26 @@ allOf:
> >      then:
> >        required:
> >          - mediatek,scp
> > +        - mediatek,vdecsys
> >  
> >        properties:
> > +        reg:
> > +          maxItems: 11
> > +
> > +        reg-names:
> > +          items:
> > +            - const: misc
> > +            - const: ld
> > +            - const: top
> > +            - const: cm
> > +            - const: ad
> > +            - const: av
> > +            - const: pp
> > +            - const: hwd
> > +            - const: hwq
> > +            - const: hwb
> > +            - const: hwg
> > +
> >          clocks:
> >            minItems: 1
> >            maxItems: 1
> > @@ -101,6 +128,9 @@ allOf:
> >          - mediatek,vpu
> >  
> >        properties:
> > +        reg:
> > +          minItems: 12
> 
> 
> What about reg-names here? They should be also defined and in sync with
> regs.

That's intentional. As described in the commit message, mt8173 will keep having
the VDEC_SYS iospace, while mt8183 won't. And we use the presence of reg-names
to tell them apart.

So, mt8173 has 12 regs, no reg-names and no syscon, while mt8183 has 11 regs,
with reg-names and the syscon.

Thanks,
Nícolas