netdev - Re: [PATCH net-next 11/14] net: stmmac: do not require snps,ps-speed for SGMII

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Message-ID: <aPD4YRH6ih93jQXH@shell.armlinux.org.uk>
Date: Thu, 16 Oct 2025 14:51:29 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Abhishek Chauhan <quic_abchauha@...cinc.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Alexis Lothore <alexis.lothore@...tlin.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Boon Khai Ng <boon.khai.ng@...era.com>,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Daniel Machon <daniel.machon@...rochip.com>,
	"David S. Miller" <davem@...emloft.net>,
	Drew Fustini <dfustini@...storrent.com>,
	Emil Renner Berthing <emil.renner.berthing@...onical.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Faizal Rahim <faizal.abdul.rahim@...ux.intel.com>,
	Furong Xu <0x1207@...il.com>, Inochi Amaoto <inochiama@...il.com>,
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	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
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	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
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	Matthew Gerlach <matthew.gerlach@...era.com>,
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	Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
	netdev@...r.kernel.org, Oleksij Rempel <o.rempel@...gutronix.de>,
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	Vladimir Oltean <olteanv@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Yu-Chun Lin <eleanor15x@...il.com>
Subject: Re: [PATCH net-next 11/14] net: stmmac: do not require snps,ps-speed
 for SGMII

On Thu, Oct 16, 2025 at 03:03:34PM +0200, Andrew Lunn wrote:
> > I don't at present, and I'm not sure what the point of updating it
> > would actually be, because this is another thing that's just broken.
> 
> > Hence, I would like this property a slow and painful^h^h^hfree death.
> > Maybe mark the property deprecated, and remove all explanation of it
> > apart from stating that it's obsolete after this patch series has
> > been merged and we've proven that it's never been useful.
> 
> And this is what i was thinking. At least mark it deprecated. If you
> want to remove the documentation late, i'm fine with that as well.

It's rather premature to do this - this series doesn't change anything
in the way that snps,ps-speed behaves.

Setting this still:
1. sets the SGMII rate adapter to take its speed configuration from the
   MAC control register rather than the in-band config.
2. enables the exchange of the SGMII in-band config.

What it doesn't do, and has never done, is to ensure that the in-band
config that is sent contains the speed and duplex information for the
SGMII link partner due to a repeated typo in the individual core sub-
drivers.

I'm not intending removing this until we have a different way to
specify it, e.g. PHY_INTERFACE_MODE_REVSGMII, but that is currently
looking unlikely. However, with PHY_INTERFACE_MODE_REVSGMII, we would
need to make the change (fix the typo bug) to publish the correct
in-band config.

I think a bit more thought is needed before going down that path,
because if we're publishing the config, is it a fixed-link. That's
something that we need to sort out in the PHY_INTERFACE_MODE_REVSGMII
discussions... if we're still going with it.

So, right now what happens here entirely depends on stuff we have
yet to make decisions on, and so marking it deprecated now is too
early.

-- 
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