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

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Andrew Lunn <andrew@lunn.ch>
Cc: "Choong Yong Liang" <yong.liang.choong@linux.intel.com>,
	"Rajneesh Bhardwaj" <irenic.rajneesh@gmail.com>,
	"David E Box" <david.e.box@linux.intel.com>,
	"Hans de Goede" <hdegoede@redhat.com>,
	"Mark Gross" <markgross@kernel.org>,
	"Jose Abreu" <Jose.Abreu@synopsys.com>,
	"Heiner Kallweit" <hkallweit1@gmail.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Marek Behún" <kabel@kernel.org>,
	"Jean Delvare" <jdelvare@suse.com>,
	"Guenter Roeck" <linux@roeck-us.net>,
	"Giuseppe Cavallaro" <peppe.cavallaro@st.com>,
	"Alexandre Torgue" <alexandre.torgue@foss.st.com>,
	"Jose Abreu" <joabreu@synopsys.com>,
	"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
	"Richard Cochran" <richardcochran@gmail.com>,
	"Philipp Zabel" <p.zabel@pengutronix.de>,
	"Alexei Starovoitov" <ast@kernel.org>,
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	"Jesse Brandeburg" <jesse.brandeburg@intel.com>,
	"Revanth Kumar Uppala" <ruppala@nvidia.com>,
	"Shenwei Wang" <shenwei.wang@nxp.com>,
	"Andrey Konovalov" <andrey.konovalov@linaro.org>,
	"Jochen Henneberg" <jh@henneberg-systemdesign.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
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	platform-driver-x86@vger.kernel.org, linux-hwmon@vger.kernel.org,
	bpf@vger.kernel.org, "Voon Wei Feng" <weifeng.voon@intel.com>,
	"Tan Tee Min" <tee.min.tan@linux.intel.com>,
	"Michael Sit Wei Hong" <michael.wei.hong.sit@intel.com>,
	"Lai Peter Jun Ann" <jun.ann.lai@intel.com>
Subject: Re: [PATCH net-next v2 0/5] TSN auto negotiation between 1G and 2.5G
Date: Thu, 21 Sep 2023 15:12:19 +0100	[thread overview]
Message-ID: <ZQxPQ9t8/TKcjlo8@shell.armlinux.org.uk> (raw)
In-Reply-To: <37fe9352-ec84-47b8-bb49-9441987ca1b9@lunn.ch>

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.

-- 
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