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Date:   Mon, 16 Jan 2023 13:47:23 +0000
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     =?iso-8859-1?Q?Bj=F8rn?= Mork <bjorn@mork.no>
Cc:     Frank Wunderlich <frank-w@public-files.de>,
        Frank Wunderlich <linux@fw-web.de>,
        linux-mediatek@lists.infradead.org,
        Alexander Couzens <lynxis@fe80.eu>,
        Felix Fietkau <nbd@nbd.name>, John Crispin <john@phrozen.org>,
        Sean Wang <sean.wang@mediatek.com>,
        Mark Lee <Mark-MC.Lee@mediatek.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] net: mtk_sgmii: implement mtk_pcs_ops
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On Mon, Jan 16, 2023 at 02:08:30PM +0100, Bj?rn Mork wrote:
> Frank Wunderlich <frank-w@public-files.de> writes:
> 
> > apart from this little problem it works much better than it actually is so imho more
> > people should test it on different platforms.
> 
> Hello!  I've been banging my head against an MT7986 board with two
> Maxlinear GPY211C phys for a while. One of those phys is connected to
> port 5 of the MT7531 switch.  This is working perfectly.
> 
> The other GPY211C is connected to the second MT7986 mac.  This one is
> giving me a headache...
> 
> I can only get the port to work at 2500Mb/s.  Changing the speed to
> anything lower looks fine in ethtool etc, but traffic is blocked.

My guess would be that the GPY PHY is using in-band SGMII negotiation
(it sets VSPEC1_SGMII_ANEN_ANRS when entering SGMII mode and clears
it in 2500base-X), but as the link is not using in-band mode on the
PCS side, the PHY never sees its in-band negotiation complete, so the
link between PCS and PHY never comes up.

Both sides need to agree on that detail.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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