netdev - Linux network PHY initial configuration for ports not 'up'

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Message-ID: <CAJ+vNU12DeT3QWp8aU+tSL-PF00yJu5M36Bmx_tw_3oXsyb76g@mail.gmail.com>
Date: Mon, 7 Oct 2024 09:48:48 -0700
From: Tim Harvey <tharvey@...eworks.com>
To: netdev <netdev@...r.kernel.org>
Subject: Linux network PHY initial configuration for ports not 'up'

Greetings,

What is the policy for configuration of network PHY's for ports that
are not brought 'up'?

I work with boards with several PHY's that have invalid link
configuration which does not get fixed until the port is brought up.
One could argue that this is fine because the port isn't up but in the
case of LED misconfiguration people wonder why the LED's are not
configured properly until the port is brought up (or they wonder why
LEDs are ilumnated at all for a port that isn't up). Another example
would be a PHY with EEE errata where EEE should be disabled but this
doesn't happen utnil the port is brought up yet while the port is
'down' a link with EEE is still established at the PHY level with a
link partner. One could also point out that power is being used to
link PHY's that should not even be linked.

In other words, should a MAC driver somehow trigger a PHY to get
initialized (as in fixups and allowing a physical link) even if the
MAC port is not up? If so, how is this done currently?

Best Regards,

Tim