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

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Message-ID: <d3ac5584-8e52-46e0-b690-ad5faa1ede61@arinc9.com>
Date: Wed, 3 Jul 2024 10:03:09 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Daniel Golle <daniel@...rotopia.org>, DENG Qingfang <dqfext@...il.com>,
 Sean Wang <sean.wang@...iatek.com>, Andrew Lunn <andrew@...n.ch>,
 Florian Fainelli <f.fainelli@...il.com>, 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 03/07/2024 02:44, 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!
> 
> Changes since v2 [2]:
>   - use macros instead of magic numbers
>   - introduce helper functions
>   - register new device on MDIO bus instead of messing with the address
>     and schedule delayed_work to unregister the "wrong" device.
>     This is a slightly different approach than suggested by Russell, but
>     imho makes things much easier than keeping the "wrong" device and
>     having to deal with keeping the removal of both devices linked.
>   - improve comments
> 
> Changes since v1 [1]:
>   - use FW_WARN as suggested.
>   - fix build on net tree which doesn't have 'mdiodev' as member of the
>     priv struct. Imho including this patch as fix makes sense to warn
>     users about broken firmware, even if the change introducing the
>     actual breakage is only present in net-next for now.
> 
> [1]: https://patchwork.kernel.org/project/netdevbpf/patch/e615351aefba25e990215845e4812e6cb8153b28.1714433716.git.daniel@makrotopia.org/
> [2]: https://patchwork.kernel.org/project/netdevbpf/patch/11f5f127d0350e72569c36f9060b6e642dfaddbb.1714514208.git.daniel@makrotopia.org/

Works on standalone MT7530, MT7621's MCM MT7530, and MT7531. From MT7621's
MCM MT7530:

[    1.357287] mt7530-mdio mdio-bus:1f: MT7530 adapts as multi-chip module
[    1.364065] mt7530-mdio mdio-bus:00: [Firmware Warn]: impossible switch MDIO address in device tree, assuming 31
[    1.374303] mt7530-mdio mdio-bus:00: probe with driver mt7530-mdio failed with error -14
[...]
[    1.448370] mt7530-mdio mdio-bus:1f: MT7530 adapts as multi-chip module
[    1.477676] mt7530-mdio mdio-bus:1f: configuring for fixed/rgmii link mode
[    1.485687] mt7530-mdio mdio-bus:1f: Link is Up - 1Gbps/Full - flow control rx/tx
[    1.493480] mt7530-mdio mdio-bus:1f: configuring for fixed/trgmii link mode
[    1.502680] mt7530-mdio mdio-bus:1f lan1 (uninitialized): PHY [mt7530-0:00] driver [MediaTek MT7530 PHY] (irq=17)
[    1.513620] mt7530-mdio mdio-bus:1f: Link is Up - 1Gbps/Full - flow control rx/tx
[    1.519671] mt7530-mdio mdio-bus:1f lan2 (uninitialized): PHY [mt7530-0:01] driver [MediaTek MT7530 PHY] (irq=18)
[    1.533072] mt7530-mdio mdio-bus:1f lan3 (uninitialized): PHY [mt7530-0:02] driver [MediaTek MT7530 PHY] (irq=19)
[    1.545042] mt7530-mdio mdio-bus:1f lan4 (uninitialized): PHY [mt7530-0:03] driver [MediaTek MT7530 PHY] (irq=20)
[    1.557031] mt7530-mdio mdio-bus:1f wan (uninitialized): PHY [mt7530-0:04] driver [MediaTek MT7530 PHY] (irq=21)

I'm not fond of the use of the non-standard term, MDIO address, instead of
"PHY Address" as described in 22.2.4.5.5 of IEEE Std 802.3-2022.
Regardless:

Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
Reviewed-by: Arınç ÜNAL <arinc.unal@...nc9.com>

Arınç