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

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Date:   Fri, 13 Mar 2020 19:16:01 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Marek Vasut <marex@...x.de>, David Jander <david@...tonic.nl>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v4 1/4] dt-bindings: net: phy: Add support for NXP TJA11xx

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.

Regards,
Oleksij

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