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

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Message-ID: <20230608200552.GA3303349-robh@kernel.org>
Date:   Thu, 8 Jun 2023 14:05:52 -0600
From:   Rob Herring <robh@...nel.org>
To:     Julien Stephan <jstephan@...libre.com>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        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>,
        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 04:05:03PM +0200, Julien Stephan wrote:
> 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. 

Why? Interrupt numbers are fixed hardware properties which go in arg 
cells.

> 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.

Once you design the binding, you don't get to change it.

Rob