Re: [PATCH net] net: mii: Fix unknown speed after link up

在 2026/10/1 5:47, Andrew Lunn 写道:

On Wed, Sep 30, 2026 at 07:38:42PM +0800, Linmao Li wrote:

quoted

mii_ethtool_get_link_ksettings() reads BMSR only once. Since
BMSR_LSTATUS is latched low, the first query after link up can
report SPEED_UNKNOWN even though the link is already up.

This is seen with r8152, which detects carrier using a MAC register
without clearing the BMSR latch. NetworkManager can then keep
reporting 0 Mb/s until the next carrier change.

Read BMSR twice to obtain the current link status, as mii_link_ok()
already does.

There is a reason for this latch behaviour, so you should not ignore
it. It ensures a link down is reported, even if it is for a short
period.

I suggest you change the code to detect link based on BMSR, not a MAC
register. Better still, throw away all the mii code and port it to
phylink. A lot of code will go away because phylink/phylib and PHY
drivers will implement it.

Hi Andrew,

Thanks for the review.

The existing read in mii_ethtool_get_link_ksettings() already clears
the latch, but I understand your concern about preserving short
link-down events.

For a focused r8152 fix, would it be acceptable to read BMSR once
before netif_carrier_on(), only when set_carrier() is transitioning
from carrier off to on? This would retain the existing MAC-based
carrier detection and clear the latched status before announcing
link up.

Or would you prefer changing carrier detection itself to use BMSR?
Could a phylink conversion be handled separately?

Thanks,
Linmao

     Andrew

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