linux-kernel - Re: [PATCH net-next v4 2/4] dt-bindings: net: Add Rx/Tx output configuration for 10base T1L

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Message-ID: <20201117203150.GA1800835@lunn.ch>
Date:   Tue, 17 Nov 2020 21:31:50 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Dan Murphy <dmurphy@...com>
Cc:     davem@...emloft.net, f.fainelli@...il.com, hkallweit1@...il.com,
        robh@...nel.org, ciorneiioana@...il.com,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v4 2/4] dt-bindings: net: Add Rx/Tx output
 configuration for 10base T1L

On Tue, Nov 17, 2020 at 02:15:53PM -0600, Dan Murphy wrote:
> Per the 802.3cg spec the 10base T1L can operate at 2 different
> differential voltages 1v p2p and 2.4v p2p. The abiility of the PHY to

ability

> drive that output is dependent on the PHY's on board power supply.
> This common feature is applicable to all 10base T1L PHYs so this binding
> property belongs in a top level ethernet document.
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>
> ---
>  Documentation/devicetree/bindings/net/ethernet-phy.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> index 6dd72faebd89..bda1ce51836b 100644
> --- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> +++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> @@ -174,6 +174,12 @@ properties:
>        PHY's that have configurable TX internal delays. If this property is
>        present then the PHY applies the TX delay.
>  
> +  max-tx-rx-p2p-microvolt:
> +    description: |
> +      Configures the Tx/Rx p2p differential output voltage for 10base-T1L PHYs.

Does it configure, or does it limit? I _think_ this is a negotiation
parameter, so the PHY might decide to do 1100mV if the link peer is
near by even when max-tx-rx-p2p-microvolt has the higher value.

     Andrew