linux-kernel - Re: [PATCH v2 3/3] dt-bindings: phy: realtek: Add the doc about the Realtek SoC USB 2.0/3.0 PHY

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Date:   Tue, 30 May 2023 07:56:57 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Stanley Chang[昌育德] 
        <stanley_chang@...ltek.com>
CC:     Conor Dooley <conor@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Flavio Suligoi <f.suligoi@...m.it>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Ray Chi <raychi@...gle.com>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] dt-bindings: phy: realtek: Add the doc about the
 Realtek SoC USB 2.0/3.0 PHY

On Tue, May 30, 2023 at 03:08:29AM +0000, Stanley Chang[昌育德] wrote:
> Hi Conor,
> 
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - realtek,usb2phy
> > > +      - realtek,rtd-usb2phy
> > > +      - realtek,rtd1295-usb2phy
> > > +      - realtek,rtd1395-usb2phy
> > > +      - realtek,rtd1619-usb2phy
> > > +      - realtek,rtd1319-usb2phy
> > > +      - realtek,rtd1619b-usb2phy
> > > +      - realtek,rtd1312c-usb2phy
> > > +      - realtek,rtd1319d-usb2phy
> > > +      - realtek,rtd1315e-usb2phy
> 
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - realtek,usb3phy
> > > +      - realtek,rtd-usb3phy
> > > +      - realtek,rtd1295-usb3phy
> > > +      - realtek,rtd1619-usb3phy
> > > +      - realtek,rtd1319-usb3phy
> > > +      - realtek,rtd1619b-usb3phy
> > > +      - realtek,rtd1319d-usb3phy
> 
> > Ignoring everything else, because I really want Krzysztof or Rob to
> > review this rather than me, but what's going on here with the
> > compatibles?
> > What hardware do "usbNphy" and "rtd-usbNphy" represent?
> > 
> > You have device-specific compatibles, which is great, but you also allow
> > only those two generic ones. I had a _brief_ look at the driver, and it
> > seems like there is no decision making done based on the compatibles,
> > only on the properties. Is that correct?
> > If it is, I would understand having "realtek,usb3phy" as a fallback
> > compatible for "realtek,rtd1619-usb3phy", but I do not get the current
> > setup.
> 
> This driver is compatible with all Realtek RTD SoCs without specifying different settings.
> So use "realtek,usb3phy" as fallback compatible for all SoCs.
> This is the compatible name we use.
> Other compatible names simply indicate that the driver supports the SoCs.

Then you should write the binding such that having fallback compatibles
is permitted. Try plugging
compatible = "realtek,rtd1295-usb2phy", "realtek,rtd-usb2phy", "realtek,usb2phy";
into your example below and see what happens.

> The name "usbNphy" and "rtd-usbNphy" seem to be more generic for all RTD SoCs,
> but they are not device-specific compatible.
> Do you have a better suggestion?

Write the binding so that having fallback compatibles in the DT actually
works, don't add the SoC-specific ones merely as indicators that those
SoCs are supported and don't permit "realtek,usbNphy" or
"realtek,rtd-usbNphy" in isolation ;)

Cheers,
Conor.

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