netdev - Re: [PATCH net-next v2 2/3] dt-bindings: dp83td510: Add binding for DP83TD510 Ethernet PHY

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Message-ID: <20201020185601.GJ139700@lunn.ch>
Date:   Tue, 20 Oct 2020 20:56:01 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Dan Murphy <dmurphy@...com>
Cc:     davem@...emloft.net, f.fainelli@...il.com, hkallweit1@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/3] dt-bindings: dp83td510: Add binding for
 DP83TD510 Ethernet PHY

> +  ti,master-slave-mode:
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    default: 0
> +    description: |
> +      Force the PHY to be configured to a specific mode.
> +      Force Auto Negotiation - 0
> +      Force Master mode at 1v p2p - 1
> +      Force Master mode at 2.4v p2p - 2
> +      Force Slave mode at 1v p2p - 3
> +      Force Slave mode at 2.4v p2p - 4
> +    enum: [ 0, 1, 2, 3, 4 ]

Is this a board hardware property? The fact value 0 means auto-neg
suggests not.

We already have ethtool configuration of master/slave for T1 PHYs:

ommit bdbdac7649fac05f88c9f7ab18121a17fb591687
Author: Oleksij Rempel <linux@...pel-privat.de>
Date:   Tue May 5 08:35:05 2020 +0200

    ethtool: provide UAPI for PHY master/slave configuration.

    This UAPI is needed for BroadR-Reach 100BASE-T1 devices. Due to lack of
    auto-negotiation support, we needed to be able to configure the
    MASTER-SLAVE role of the port manually or from an application in user
    space.

Please can you look at using that UAPI.

I assume that 1v p2p is the voltage of the signal put onto the twisted
pair? I know the Marvell 1000BaseT PHYs allow this to be configured as
well, but just downwards to save power. Maybe a PHY tunable would be
better?

Humm. Are 1v and 2.4v advertised so it can be auto negotiated? Maybe a
PHY tunable is not correct? Is this voltage selection actually more
like pause and EEE?

	Andrew