linux-kernel - Re: [PATCH net-next v3 2/4] dt-bindings: net: Add Rx/Tx output configuration for 10base T1L

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Date:   Wed, 4 Nov 2020 16:08:31 -0600
From:   Rob Herring <robh@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Dan Murphy <dmurphy@...com>, davem@...emloft.net,
        f.fainelli@...il.com, hkallweit1@...il.com,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/4] dt-bindings: net: Add Rx/Tx output
 configuration for 10base T1L

On Fri, Oct 30, 2020 at 08:56:55PM +0100, Andrew Lunn wrote:
> On Fri, Oct 30, 2020 at 12:29:48PM -0500, 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
> > drive that output is dependent on the PHY's on board power supply.
> 
> Hi Dan
> 
> So this property is about the board being able to support the needed
> voltages? The PHY is not forced into 2.4v p2p, it just says the PHY
> can operate at 2.4v and the board will not melt, blow a fuse, etc?
> 
> I actually think it is normal to specify the reverse. List the maximum
> that device can do because of board restrictions. e.g.
> 
> - maximum-power-milliwatt : Maximum module power consumption
>   Specifies the maximum power consumption allowable by a module in the
>   slot, in milli-Watts.  Presently, modules can be up to 1W, 1.5W or 2W.
> 
> - max-link-speed:
>    If present this property specifies PCI gen for link capability.  Host
>    drivers could add this as a strategy to avoid unnecessary operation for
>    unsupported link speed, for instance, trying to do training for
>    unsupported link speed, etc.  Must be '4' for gen4, '3' for gen3, '2'
>    for gen2, and '1' for gen1. Any other values are invalid.
> 
>  - max-microvolt : The maximum voltage value supplied to the haptic motor.
>                 [The unit of the voltage is a micro]
> 
> So i think this property should be
> 
>    max-tx-rx-p2p = <1000>;
> 
> to limit it to 1000mv p2p because of board PSU limitations, and it is
> free to do 22000mv is the property is not present.

'-microvolt' suffix please.

> 
>    Andrew
>