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

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Message-ID: <988cd2d7-e9f2-3947-7fcc-3da7fef7e34b@gmail.com>
Date:   Wed, 27 Jan 2021 08:04:02 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     Corinna Vinschen <vinschen@...hat.com>, netdev@...r.kernel.org,
        sassmann@...hat.com
Subject: Re: [PATCH net v2 7/7] igc: fix link speed advertising

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?