linux-kernel - Re: [PATCH net-next v3 0/5] TSN auto negotiation between 1G and 2.5G

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Message-ID: <4caade36-d4be-4670-ac79-d9d00488293d@lunn.ch>
Date:   Thu, 21 Sep 2023 15:14:59 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Choong Yong Liang <yong.liang.choong@...ux.intel.com>
Cc:     Rajneesh Bhardwaj <irenic.rajneesh@...il.com>,
        David E Box <david.e.box@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Marek Behún <kabel@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Richard Cochran <richardcochran@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
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        John Fastabend <john.fastabend@...il.com>,
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        Jon Hunter <jonathanh@...dia.com>,
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        Shenwei Wang <shenwei.wang@....com>,
        Andrey Konovalov <andrey.konovalov@...aro.org>,
        Jochen Henneberg <jh@...neberg-systemdesign.com>,
        David E Box <david.e.box@...el.com>,
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        Simon Horman <simon.horman@...igine.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        platform-driver-x86@...r.kernel.org, linux-hwmon@...r.kernel.org,
        bpf@...r.kernel.org, Voon Wei Feng <weifeng.voon@...el.com>,
        Tan Tee Min <tee.min.tan@...ux.intel.com>,
        Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>,
        Lai Peter Jun Ann <jun.ann.lai@...el.com>
Subject: Re: [PATCH net-next v3 0/5] TSN auto negotiation between 1G and 2.5G

> Auto-negotiation between 10, 100, 1000Mbps will use
> in-band auto negotiation. Auto-negotiation between 10/100/1000Mbps and
> 2.5Gbps will work as the following proposed flow, the stmmac driver reads
> the PHY link status registers then identifies the negotiated speed.

I don't think you replied to my comment.

in-band is just an optimisation. It in theory allows you to avoid a
software path, the PHY driver talking to the MAC driver about the PHY
status. As an optimisation, it is optional. Linux has the software
path and the MAC driver you are using basically has it implemented.

Why use this odd mix of in-band and out of band? It seems the change
will be simpler if you just use the out of band method all the time
and ignore in-band.

	Andrew