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Date: Wed, 10 Jan 2024 20:23:58 +0200
From: Vladimir Oltean <olteanv@gmail.com>
To: =?utf-8?B?QXLEsW7DpyDDnE5BTA==?= <arinc.unal@arinc9.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>,
	Simon Horman <horms@kernel.org>,
	Daniel Golle <daniel@makrotopia.org>,
	Landen Chao <Landen.Chao@mediatek.com>,
	DENG Qingfang <dqfext@gmail.com>,
	Sean Wang <sean.wang@mediatek.com>, Andrew Lunn <andrew@lunn.ch>,
	Florian Fainelli <f.fainelli@gmail.com>,
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	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
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	Bartel Eerdekens <bartel.eerdekens@constell8.be>,
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Subject: Re: [PATCH net-next 07/15] net: dsa: mt7530: do not run
 mt7530_setup_port5() if port 5 is disabled
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On Wed, Jan 10, 2024 at 10:26:54AM +0300, Arınç ÜNAL wrote:
> > Are there existing systems that use PHY muxing? The possible problem I
> > see is breaking those boards which have a phy-handle on gmac5, if the
> > mt7530 driver is no longer going to modify its HWTRAP register.
> 
> Ah see, for PHY muxing, the driver actually wants the phy-handle to be put
> on the SoC MAC, and the PHY to be defined on the SoC ethernet's MDIO bus.
> We don't even define gmac5 as a port on the switch dt-bindings.

I noticed that from the code already. Maybe I shouldn't have said
"gmac5" when I meant "the GMAC attached to switch port 5, aka GMAC0".
I was under the impression that you were also using this slightly
incorrect terminology, to keep a numerical association between the CPU
port number and its directly attached GMAC.

> While none of the DTs on the Linux repository utilise this, some of the
> mt7621 DTs on OpenWrt do. The change in behaviour will only be that phy0/4
> will be inaccessible from the SoC MAC's network interface. I de-facto
> maintain the mt7621 device tree source files there. I intend to revert it
> along with adding port 5 as a CPU port so that the conduit changing feature
> becomes available.

If OpenWrt kernels are always shipped in tandem with updated device
trees (i.e. no Arm SystemReady IR platforms, where the DT is provided by
U-Boot), I won't oppose to retracting features described via DT if their
platform maintainers agree in a wide enough circle that the breakage is
manageable.

BTW, besides OpenWrt, what other software is deployed on these SoCs
typically?