linux-kernel - Re: [PATCH net-next v2 0/5] TSN auto negotiation between 1G and 2.5G

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Message-ID: <ZQxPQ9t8/TKcjlo8@shell.armlinux.org.uk>
Date:   Thu, 21 Sep 2023 15:12:19 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
        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>,
        "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>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Wong Vee Khee <veekhee@...le.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Revanth Kumar Uppala <ruppala@...dia.com>,
        Shenwei Wang <shenwei.wang@....com>,
        Andrey Konovalov <andrey.konovalov@...aro.org>,
        Jochen Henneberg <jh@...neberg-systemdesign.com>,
        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 v2 0/5] TSN auto negotiation between 1G and 2.5G

On Thu, Sep 21, 2023 at 03:21:00PM +0200, Andrew Lunn wrote:
> > Hi Andrew,
> > 
> > After conducting a comprehensive study, it seems that implementing
> > out-of-band for all link modes might not be feasible. I may have missed some
> > key aspects during my analysis.
> > 
> > Would you be open to sharing a high-level idea of how we could potentially
> > make this feasible? Your insights would be greatly appreciated.
> 
> stmmac_mac_link_up() gets passed interface, speed and duplex. That
> tells you what the PHY has negotiated. Is there anything else you need
> to know?

The problem is... the stmmac driver is utter bollocks - that information
is *not* passed to the BSP. Instead, stmmac parse and store information
such as the PHY interface mode at initialisation time. BSPs also re-
parse and store e.g. the PHY interface mode at initialisation time.
The driver ignores what it gets from phylink.

The driver is basically utter crap. That's an area I _had_ patches to
clean up. I no longer do. stmmac is crap crap crap and will stay crap
until they become more receptive to patches to fix it, even if the
patches are not 100% to their liking but are in fact correct. Maybe
if I ever decide to touch that driver in the future. Which I doubt
given my recent experience.

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