linux-kernel - Re: [PATCH net-next 07/15] net: dsa: mt7530: do not run mt7530_setup

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Message-ID: <009fec43-0669-419e-a3a9-ce54c676a324@arinc9.com>
Date: Thu, 11 Jan 2024 13:22:12 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Dan Carpenter <dan.carpenter@...aro.org>, Simon Horman
 <horms@...nel.org>, Daniel Golle <daniel@...rotopia.org>,
 Landen Chao <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>,
 Sean Wang <sean.wang@...iatek.com>, Andrew Lunn <andrew@...n.ch>,
 Florian Fainelli <f.fainelli@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org,
 Frank Wunderlich <frank-w@...lic-files.de>,
 Bartel Eerdekens <bartel.eerdekens@...stell8.be>, mithat.guner@...ont.com,
 erkin.bozoglu@...ont.com
Subject: Re: [PATCH net-next 07/15] net: dsa: mt7530: do not run
 mt7530_setup_port5() if port 5 is disabled

On 10.01.2024 21:23, Vladimir Oltean wrote:
> 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.

I will see to this when the time comes.

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

Other than OpenWrt which is widely used for these SoCs for its ease of
flashing and upgrading, compatibility with legacy U-boot versions that
usually come with any vendor making a product out of these SoCs, I can only
talk about what I deploy to run Linux. I use mainline U-Boot along with the
device trees from the Linux repository to boot mainline Linux kernels with
Buildroot as the filesystem.

Arınç