netdev - Re: [PATCH net v2 7/7] igc: fix link speed advertising

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Date:   Wed, 27 Jan 2021 23:34:11 +0000
From:   "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
To:     "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "vinschen@...hat.com" <vinschen@...hat.com>
Subject: Re: [PATCH net v2 7/7] igc: fix link speed advertising

On Wed, 2021-01-27 at 08:04 +0100, Heiner Kallweit wrote:
> On 26.01.2021 23:10, Tony Nguyen wrote:
> > From: Corinna Vinschen <vinschen@...hat.com>
> > 
> > Link speed advertising in igc has two problems:
> > 
> > - When setting the advertisement via ethtool, the link speed is
> > converted
> >   to the legacy 32 bit representation for the intel PHY code.
> >   This inadvertently drops ETHTOOL_LINK_MODE_2500baseT_Full_BIT
> > (being
> >   beyond bit 31).  As a result, any call to `ethtool -s ...' drops
> > the
> >   2500Mbit/s link speed from the PHY settings.  Only reloading the
> > driver
> >   alleviates that problem.
> > 
> >   Fix this by converting the ETHTOOL_LINK_MODE_2500baseT_Full_BIT
> > to the
> >   Intel PHY ADVERTISE_2500_FULL bit explicitly.
> > 
> > - Rather than checking the actual PHY setting, the
> > .get_link_ksettings
> >   function always fills link_modes.advertising with all link speeds
> >   the device is capable of.
> > 
> >   Fix this by checking the PHY autoneg_advertised settings and
> > report
> >   only the actually advertised speeds up to ethtool.
> > 
> > Fixes: 8c5ad0dae93c ("igc: Add ethtool support")
> > Signed-off-by: Corinna Vinschen <vinschen@...hat.com>
> > Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> > ---
> >  drivers/net/ethernet/intel/igc/igc_ethtool.c | 24 +++++++++++++++-
> > ----
> >  1 file changed, 18 insertions(+), 6 deletions(-)
> > 
> 
> Would switching to phylib be a mid-term option for you?
> This could save quite some code and you'd get things like proper
> 2.5Gbps
> handling out of the box. Or is there anything that prevents using
> phylib?

Phylib is something we can look into though we have some device
specific quirks that we would need to see how it could be handled.
Since this is fixing a current problem and any transition to phylib
would not be immediate, I think this patch should be accepted while we
investigate phylib.

Thanks,
Tony