netdev - 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>,
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	Marek Behún <kabel@...nel.org>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
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	Alexandre Torgue <alexandre.torgue@...s.st.com>,
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	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,
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	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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