Re: [PATCH net v1 1/1] net: phylink: keep initial advertising settings

[Anandu Padinhare]

On Wed, Nov 04, 2026 at 01:55:09PM +0100, Thilo Zirnstein wrote:
> Connecting the phy while ndo_open callback seems to be a common pattern,
> affected drivers are:
>
> * macb
> * r8169
> * stmmac
> * tn40xx

Hi Thilo,

Results from an ADSP-SC598 board (stmmac, RGMII, TI DP83867 PHY) with
a 6.18-based kernel, with and without this patch.

1. The case in the commit message is fixed, with both the dp83867 and
   the generic PHY driver:

     ip link set eth0 down
     ethtool -s eth0 speed 100 duplex full autoneg on
     ip link set eth0 up

   Without the patch the link comes up at 1000 Mb/s; with it, at
   100 Mb/s.

2. In that same case the pause bits are lost: with the patch the link
   comes up with flow control off; without it, pause stays on. Same
   with both PHY drivers. While the interface is down, ethtool shows
   no advertised modes and no pause, before and after the
   "ethtool -s" (phylink_ethtool_ksettings_get() reports none when no
   PHY is attached), and the AND then drops the pause bits the PHY
   advertises.

3. Sashiko's sequences (a) and (b) both reproduce with the dp83867
   driver:

   (a) advertise 100baseT/Full while up, ifdown/ifup: 100 Mb/s.
       advertise 10/100/1000baseT/Full while up: 1000 Mb/s.
       ifdown/ifup: back to 100 Mb/s, advertising only 100baseT/Full.

   (b) continuing, advertise 1000baseT/Full while up: 1000 Mb/s.
       ifdown/ifup: "Advertised link modes: Not reported", and the
       link stays down (NO-CARRIER).

   Without the patch, both keep the last setting: (a) comes back at
   1000 Mb/s, and (b) at 1000 Mb/s with 1000baseT/Full advertised.

Happy to test a v2 on this board.