On Tue, Mar 31, 2026 at 12:46:27AM +0200, Nicolai Buchwitz wrote:

Enable auto-downshift from 1000BASE-T to 100BASE-TX after 2 failed
auto-negotiation attempts by default. This ensures that links with
faulty or missing cable pairs (C and D) fall back to 100Mbps without
requiring userspace configuration.

Users can override or disable downshift at runtime:

  ethtool --set-phy-tunable eth0 downshift off

Signed-off-by: Nicolai Buchwitz <redacted>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>

I'm slightly concerned by this commit. ->config_init() is called when
the netdev attaches the PHY, and also during the resume path - and it's
the second one which I believe is a problem here.

If the user has configured the downshift, it is reasonable for the user
to expect the setting to be preserved over a suspend/resume. However,
by placing this code in ->config_init(), you will overwrite the user's
setting when the system resumes.

-- 
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