From: Helmut Grohne <helmut.gro...@intenta.de>
Date: Tue, 14 Jul 2020 10:25:42 +0200
> When doing "ip link set dev ... up" for a ksz9477 backed link,
> ksz9477_phy_setup is called and it calls phy_remove_link_mode to remove
> 1000baseT HDX. During phy_remove_link_mode, phy_advertise_supported is
> called.
>
> If one wants to advertise fewer modes than the supported ones, one
> usually reduces the advertised link modes before upping the link (e.g.
> by passing an appropriate .link file to udev). However upping
> overrwrites the advertised link modes due to the call to
> phy_advertise_supported reverting to the supported link modes.
>
> It seems unintentional to have phy_remove_link_mode enable advertising
> bits and it does not match its description in any way. Instead of
> calling phy_advertise_supported, we should simply clear the link mode to
> be removed from both supported and advertising.
>
> Signed-off-by: Helmut Grohne <helmut.gro...@intenta.de>
> Fixes: 41124fa64d4b29 ("net: ethernet: Add helper to remove a supported link
> mode")
The problem is that we can't allow the advertised setting to exceed
what is in the supported list.
That's why this helper is coded this way from day one.
