netdev - Re: [PATCH net v3] net: dsa: mt7530: fix impossible MDIO address and issue warning

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Message-ID: <5c92dcae-ec10-4652-a5e4-3f050774fc8b@gmail.com>
Date: Thu, 4 Jul 2024 16:46:29 +0200
From: Florian Fainelli <f.fainelli@...il.com>
To: Daniel Golle <daniel@...rotopia.org>, Arınç ÜNAL
 <arinc.unal@...nc9.com>, DENG Qingfang <dqfext@...il.com>,
 Sean Wang <sean.wang@...iatek.com>, Andrew Lunn <andrew@...n.ch>,
 Vladimir Oltean <olteanv@...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>,
 Landen Chao <Landen.Chao@...iatek.com>, Frank Wunderlich <linux@...web.de>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 regressions@...ts.linux.dev
Subject: Re: [PATCH net v3] net: dsa: mt7530: fix impossible MDIO address and
 issue warning

On 7/3/2024 12:44 AM, Daniel Golle wrote:
> The MDIO address of the MT7530 and MT7531 switch ICs can be configured
> using bootstrap pins. However, there are only 4 possible options for the
> switch itself: 7, 15, 23 and 31. As in MediaTek's SDK the address of the
> switch is wrongly stated in the device tree as 0 (while in reality it is
> 31), warn the user about such broken device tree and make a good guess
> what was actually intended.
> 
> This is imporant also to not break compatibility with older Device Trees
> as with commit 868ff5f4944a ("net: dsa: mt7530-mdio: read PHY address of
> switch from device tree") the address in device tree will be taken into
> account, while before it was hard-coded to 0x1f.
> 
> Fixes: b8f126a8d543 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
> Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> ---
> Only tested on BPi-R3 (with various deliberately broken DT) for now!

This seems like a whole lot of code just to auto-magically fix an issue 
that could be caught with a warning. I appreciate that most of these 
devices might be headless, and therefore having some attempt at getting 
functional networking goes a long way into allowing users to correct 
their mistakes.
-- 
Florian