netdev - Re: [RFC PATCH 2/3] dt-bindings: net: phy: Add support for AT803X

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Message-ID: <d68a8bef6f7d5193e7d373311c8045d7@walle.cc>
Date:   Thu, 31 Oct 2019 18:14:16 +0100
From:   Michael Walle <michael@...le.cc>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 2/3] dt-bindings: net: phy: Add support for AT803X

Am 2019-10-31 17:45, schrieb Florian Fainelli:
> On 10/30/19 5:14 PM, Michael Walle wrote:
>>> So we can later add atheros,rgmii-io-2v5. That might need a regulator
>>> as well. Maybe add that 2.5V is currently not supported.
>> 
>> There is no special setting for the 2.5V mode. This is how it works: 
>> there is one voltage pad for the RGMII interface. Either you connect 
>> this pad to a 2.5V voltage or you leave it open (well you would 
>> connect some decoupling Cs). If you leave it open the internal LDO, 
>> which seems to be enabled in any case takes over, supplying 1.5V. then 
>> there is a bit in the debug register which can switch the internal LDO 
>> to 1.8V. So if you'll use 2.5V the bit is irrelevant.
>> 
>> Like I said maybe a "rgmii-io-microvolts" is a better property and 
>> only in the 1800000 setting would turn on this bit. but then both 
>> other setting would be a noop.
> 
> That would align with the regulator subsystem units, but maybe you
> should have the PHY driver be a regulator provider for itself so you 
> can
> chose wether you want to operate at 1.5V or 1.8V, or you have an
> external regulator providing I/O supplies. That would make the whole
> thing consistent from the driver's perspective and would not 
> necessarily
> be too far fetched from a HW description perspective?

Sounds good. But again, I'm not too familiar with that. Could you give 
an
example how the device tree would look like then? Maybe that way I can 
work
myself through that regulator stuff.

-- 
michael