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 11:20:35 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Andrew Lunn <andrew@...n.ch>
Cc:     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 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>;
	};
};
-- 
Florian