linux-kernel - Re: [PATCH v3 2/3] dt-bindings: phy: add mediatek MIPI CD-PHY module v0.5

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Date:   Wed, 24 May 2023 16:05:03 +0200
From:   Julien Stephan <jstephan@...libre.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     mkorpershoek@...libre.com, khilman@...libre.com,
        Florian Sylvestre <fsylvestre@...libre.com>,
        Andy Hsieh <andy.hsieh@...iatek.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linux-phy@...ts.infradead.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>
Subject: Re: [PATCH v3 2/3] dt-bindings: phy: add mediatek MIPI CD-PHY module
 v0.5

On Wed, May 24, 2023 at 11:45:30AM +0200, AngeloGioacchino Del Regno wrote:
> Il 24/05/23 10:30, Julien Stephan ha scritto:
> > From: Florian Sylvestre <fsylvestre@...libre.com>
> >
> > This adds the bindings, for the MIPI CD-PHY module v0.5 embedded in
> > some Mediatek soc, such as the mt8365
> >
> > Signed-off-by: Florian Sylvestre <fsylvestre@...libre.com>
> > Signed-off-by: Julien Stephan <jstephan@...libre.com>
> > ---
> >   .../bindings/phy/mediatek,mt8365-csi-rx.yaml  | 67 +++++++++++++++++++
> >   MAINTAINERS                                   |  6 ++
> >   2 files changed, 73 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/phy/mediatek,mt8365-csi-rx.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/phy/mediatek,mt8365-csi-rx.yaml b/Documentation/devicetree/bindings/phy/mediatek,mt8365-csi-rx.yaml
> > new file mode 100644
> > index 000000000000..a1bd96a98051
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/mediatek,mt8365-csi-rx.yaml
> > @@ -0,0 +1,67 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +# Copyright (c) 2023 MediaTek, BayLibre
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/phy/mediatek,mt8365-csi-rx.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Mediatek Sensor Interface MIPI CSI CD-PHY
> > +
> > +maintainers:
> > +  - Julien Stephan <jstephan@...libre.com>
> > +  - Andy Hsieh <andy.hsieh@...iatek.com>
> > +
> > +description:
> > +  The SENINF CD-PHY is a set of CD-PHY connected to the SENINF CSI-2
> > +  receivers. The number of PHYs depends on the SoC model.
> > +  Depending on the SoC model, each PHYs can be either CD-PHY or D-PHY only
> > +  capable.
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - mediatek,mt8365-csi-rx
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  '#phy-cells':
> > +    const: 0
> > +
> > +  mediatek,phy-type:
>
> Instead of declaring a phy-type here like this, can't we instead declare that in
> the phy cells, like we're doing with MTK TPHY and like other non-MediaTek PHYs are
> already doing?
>
> device {
> 	...
> 	phys = <&csi0_rx PHY_TYPE_CDPHY>;
> 	...
> }
>
> Regards,
> Angelo
>
>

Hi Angelo,

This is a hardware property that is not dynamic, so IMHO it doesn't make sense
to use phy argument for that. Some driver already use a 'phy-type'
property (such as phy-cadence-torrent.yaml).

I was thinking of using phy argument on future upgrade when driver will
support D-PHY and C-PHY modes so the phy user will be able to choose the
mode.

Does it makes sense?

Best
Julien