linux-kernel - Re: [PATCH net-next 05/15] net: dsa: mt7530: improve code path for setting up port 5

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Message-ID: <5e95a436-189f-412e-b409-89a003003292@arinc9.com>
Date:   Sat, 2 Dec 2023 11:36:03 +0300
From:   Arınç ÜNAL <arinc.unal@...nc9.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
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>,
        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>, 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 05/15] net: dsa: mt7530: improve code path for
 setting up port 5

On 18.11.2023 17:41, Russell King (Oracle) wrote:
> On Sat, Nov 18, 2023 at 03:31:55PM +0300, Arınç ÜNAL wrote:
>> There're two code paths for setting up port 5:
>>
>> mt7530_setup()
>> -> mt7530_setup_port5()
>>
>> mt753x_phylink_mac_config()
>> -> mt753x_mac_config()
>>     -> mt7530_mac_config()
>>        -> mt7530_setup_port5()
>>
>> Currently mt7530_setup_port5() from mt7530_setup() always runs. If port 5
>> is used as a CPU, DSA, or user port, mt7530_setup_port5() from
>> mt753x_phylink_mac_config() won't run. That is because priv->p5_interface
>> set on mt7530_setup_port5() will match state->interface on
>> mt753x_phylink_mac_config() which will stop running mt7530_setup_port5()
>> again.
>>
>> Therefore, mt7530_setup_port5() will never run from
>> mt753x_phylink_mac_config().
>>
>> Address this by not running mt7530_setup_port5() from mt7530_setup() if
>> port 5 is used as a CPU, DSA, or user port. This driver isn't in the
>> dsa_switches_apply_workarounds[] array so phylink will always be present.
>>
>> For the cases of PHY muxing or the port being disabled, call
>> mt7530_setup_port5() from mt7530_setup(). mt7530_setup_port5() from
>> mt753x_phylink_mac_config() won't run when port 5 is disabled or used for
>> PHY muxing as port 5 won't be defined on the devicetree.
> 
> ... and this should state why this needs to happen - in other words,
> the commit message should state why is it critical that port 5 is
> always setup.

Actually, port 5 must not always be setup. With patch 7, I explain this
while preventing mt7530_setup_port5() from running if port 5 is disabled.

Arınç