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

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Date:   Wed, 7 Jun 2023 15:58:34 -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 3/6] media: dt-bindings: mediatek,vcodec: Remove VDEC_SYS
 for mt8183

On Tue, Jun 06, 2023 at 11:16:12AM +0200, Krzysztof Kozlowski wrote:
> On 05/06/2023 18:20, 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 clock that indicates the hardware
> > is active, remove the VDEC_SYS register space from the binding and
> > describe an extra clock 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>
> > ---
> > 
> >  .../media/mediatek,vcodec-decoder.yaml        | 29 +++++++++++++++++--
> >  1 file changed, 27 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml b/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml
> > index 6447e6c86f29..36a53b2484d6 100644
> > --- a/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml
> > +++ b/Documentation/devicetree/bindings/media/mediatek,vcodec-decoder.yaml
> > @@ -21,17 +21,21 @@ properties:
> >        - mediatek,mt8183-vcodec-dec
> >  
> >    reg:
> > +    minItems: 11
> >      maxItems: 12
> >  
> > +  reg-names:
> > +    minItems: 11
> 
> maxItems
> 
> > +
> >    interrupts:
> >      maxItems: 1
> >  
> >    clocks:
> > -    minItems: 1
> > +    minItems: 2
> 
> It does not make any sense. Just two patches ago you made it 1! Don't
> add incorrect values which are immediately changed in the same patchset.

It's not an incorrect value. At the point that commit was added, the first reg
was still VDEC_SYS, so an active clock wasn't required. This commit removes the
VDEC_SYS reg, and so the active clock becomes necessary. Splitting it like this
made the most sense to me, and I thought it would also simplify review. But
since it seems to be a problem I'll merge commit 1 with this one in v2 to avoid
changing the number of clocks twice.

> 
> >      maxItems: 8
> >  
> >    clock-names:
> > -    minItems: 1
> > +    minItems: 2
> >      maxItems: 8
> >  
> >    assigned-clocks: true
> > @@ -84,6 +88,24 @@ allOf:
> >          clock-names:
> >            items:
> >              - const: vdec
> > +            - const: active
> > +
> > +        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
> >  
> >    - if:
> >        properties:
> > @@ -108,6 +130,9 @@ allOf:
> >              - const: venc_lt_sel
> >              - const: vdec_bus_clk_src
> >  
> > +        reg:
> > +          minItems: 12
> 
> so max can be 1000?

No, there's 'maxItems: 12' up above in the general case.

Thanks,
Nícolas