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

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Message-ID: <20200320230504.GA30209@bogus>
Date:   Fri, 20 Mar 2020 17:05:04 -0600
From:   Rob Herring <robh@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Marek Vasut <marex@...x.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.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 Tue, Mar 17, 2020 at 12:48:47PM -0700, Florian Fainelli wrote:
> 
> 
> On 3/17/2020 4:56 AM, Oleksij Rempel wrote:
> > On Fri, Mar 13, 2020 at 07:53:27PM +0100, Oleksij Rempel wrote:
> >> 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?
> 
> It's not for me to decide, I was hoping the Device Tree maintainers
> could chime in, your current approach would certainly work although it
> feels visually awkward.

Something like this is what I'd do:

ethernet-phy@4 {
  compatible = "nxp,tja1102";
  reg = <4 5>;
};

Rob