Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20211017171657.85724-1-erik@kryo.se> <YW7idC0/+zq6dDNv@lunn.ch>
In-Reply-To: <YW7idC0/+zq6dDNv@lunn.ch>
From:   Erik Ekman <erik@kryo.se>
Date:   Tue, 19 Oct 2021 19:41:46 +0200
Message-ID: <CAGgu=sCBUU29tkjqOP9j7EZJL-T4O6NoTDNB+-PFNhUkOTdWuw@mail.gmail.com>
Subject: Re: [PATCH] sfc: Fix reading non-legacy supported link modes
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     Edward Cree <ecree.xilinx@gmail.com>,
        Martin Habets <habetsm.xilinx@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, 19 Oct 2021 at 17:21, Andrew Lunn <andrew@lunn.ch> wrote:
>
> On Sun, Oct 17, 2021 at 07:16:57PM +0200, Erik Ekman wrote:
> > Everything except the first 32 bits was lost when the pause flags were
> > added. This makes the 50000baseCR2 mode flag (bit 34) not appear.
> >
> > I have tested this with a 10G card (SFN5122F-R7) by modifying it to
> > return a non-legacy link mode (10000baseCR).
>
> Does this need a Fixes: tag? Should it be added to stable?
>

The speed flags in use that can be lost are for 50G and 100G.
The affected devices are ones based on the Solarflare EF100 networking
IP in Xilinx FPGAs supporting 10/25/40/100-gigabit.
I don't know how widespread these are, and if there might be enough
users for adding this to stable.

The gsettings api code for sfc was added in 7cafe8f82438ced6d ("net:
sfc: use new api ethtool_{get|set}_link_ksettings")
and the bug was introduced then, but bits would only be lost after
support for 25/50/100G was added in
5abb5e7f916ee8d2d ("sfc: add bits for 25/50/100G supported/advertised speeds").
Not sure which of these should be used for a Fixes tag.

I only noticed this because I was using newer flags for signaling
1G/10G fibre support in my other patch.

Thanks
/Erik