linux-kernel - Re: [PATCH v4 1/4] dt-bindings: net: phy: Add support for NXP TJA11xx

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Message-ID: <20200313185327.nawcp2imfldyhpqa@pengutronix.de>
Date:   Fri, 13 Mar 2020 19:53:27 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Mark Rutland <mark.rutland@....com>,
        Marek Vasut <marex@...x.de>, devicetree@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH v4 1/4] dt-bindings: net: phy: Add support for NXP TJA11xx

On Fri, Mar 13, 2020 at 11:20:35AM -0700, Florian Fainelli wrote:
> 
> 
> On 3/13/2020 11:16 AM, Oleksij Rempel wrote:
> > On Fri, Mar 13, 2020 at 07:10:56PM +0100, Andrew Lunn wrote:
> >>>> diff --git a/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml b/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml
> >>>> new file mode 100644
> >>>> index 000000000000..42be0255512b
> >>>> --- /dev/null
> >>>> +++ b/Documentation/devicetree/bindings/net/nxp,tja11xx.yaml
> >>>> @@ -0,0 +1,61 @@
> >>>> +# SPDX-License-Identifier: GPL-2.0+
> >>>> +%YAML 1.2
> >>>> +---
> >>>> +$id: http://devicetree.org/schemas/net/nxp,tja11xx.yaml#
> >>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>> +
> >>>> +title: NXP TJA11xx PHY
> >>>> +
> >>>> +maintainers:
> >>>> +  - Andrew Lunn <andrew@...n.ch>
> >>>> +  - Florian Fainelli <f.fainelli@...il.com>
> >>>> +  - Heiner Kallweit <hkallweit1@...il.com>
> >>>> +
> >>>> +description:
> >>>> +  Bindings for NXP TJA11xx automotive PHYs
> >>>> +
> >>>> +allOf:
> >>>> +  - $ref: ethernet-phy.yaml#
> >>>> +
> >>>> +patternProperties:
> >>>> +  "^ethernet-phy@[0-9a-f]+$":
> >>>> +    type: object
> >>>> +    description: |
> >>>> +      Some packages have multiple PHYs. Secondary PHY should be defines as
> >>>> +      subnode of the first (parent) PHY.
> >>>
> >>>
> >>> There are QSGMII PHYs which have 4 PHYs embedded and AFAICT they are
> >>> defined as 4 separate Ethernet PHY nodes and this would not be quite a
> >>> big stretch to represent them that way compared to how they are.
> >>>
> >>> I would recommend doing the same thing and not bend the MDIO framework
> >>> to support the registration of "nested" Ethernet PHY nodes.
> >>
> >> Hi Florian
> >>
> >> The issue here is the missing PHY ID in the secondary PHY. Because of
> >> that, the secondary does not probe in the normal way. We need the
> >> primary to be involved to some degree. It needs to register it. What
> >> i'm not so clear on is if it just needs to register it, or if these
> >> sub nodes are actually needed, given the current code.
> > 
> > There are a bit more dependencies:
> > - PHY0 is responsible for health monitoring. If some thing wrong, it may
> >   shut down complete chip.
> > - We have shared reset. It make no sense to probe PHY1 before PHY0 with
> >   more controlling options will be probed
> > - It is possible bat dangerous to use PHY1 without PHY0.
> 
> probing is a software problem though. If we want to describe the PHY
> package more correctly, we should be using a container node, something
> like this maybe:
>
> phy-package {
> 	compatible = "nxp,tja1102";
> 
> 	ethernet-phy@4 {
> 		reg = <4>;
> 	};
> 
> 	ethernet-phy@5 {
> 		reg = <5>;
> 	};
> };

Yes, this is almost the same as it is currently done:

phy-package {
	reg = <4>;
 
 	ethernet-phy@5 {
 		reg = <5>;
 	};
};

Because the primary PHY0 can be autodetected by the bus scan.
But I have nothing against your suggestions. Please, some one should say the
last word here, how exactly it should be implemented?

Regards,
Oleksij
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