linux-kernel - Re: [PATCH net-next] net: dsa: mt7530: register OF node for internal MDIO bus

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Message-ID: <bdbe24b2-30f6-48fa-b6eb-a1ae3afe9076@arinc9.com>
Date: Wed, 27 Dec 2023 22:51:08 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: 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>,
 David Bauer <mail@...id-bauer.net>, mithat.guner@...ont.com,
 erkin.bozoglu@...ont.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next] net: dsa: mt7530: register OF node for internal
 MDIO bus

On 27.12.2023 22:11, Vladimir Oltean wrote:
> On Sun, Dec 24, 2023 at 10:37:12AM +0300, Arınç ÜNAL wrote:
>> If the MDIO bus of the switch is defined on the devicetree, the
>> (!ds->user_mii_bus && ds->ops->phy_read) check in dsa_switch_setup will be
>> true so the MDIO bus will be attempted to be registered again, resulting in
>> a kernel panic.
> 
> Where does mt7530 provide ds->ops->phy_read() in upstream?

Sorry, that's a misdiagnosis from my part. There's indeed no
ds->ops->phy_read() or ds->ops->phy_write(). I should know that as I have
intensively studied the MDIO bus registration on all DSA subdrivers. The
issue is at mt7530_setup_mdio_irq():

ds->user_mii_bus->irq[p] = irq;

I didn't realise ds->user_mii_bus is also used to store irq mapping for
each PHY. Should we agree that user_mii_bus is needed for all cases or make
another way to store the irq mappings?

Arınç