linux-kernel - Re: [PATCH net v4 2/7] net: dsa: mt7530: fix trapping frames with multiple CPU ports on MT7530

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Date:   Tue, 13 Jun 2023 20:16:59 +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>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Bartel Eerdekens <bartel.eerdekens@...stell8.be>,
        mithat.guner@...ont.com, erkin.bozoglu@...ont.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net v4 2/7] net: dsa: mt7530: fix trapping frames with
 multiple CPU ports on MT7530

On 13.06.2023 00:09, Russell King (Oracle) wrote:
> On Mon, Jun 12, 2023 at 10:59:40AM +0300, arinc9.unal@...il.com wrote:
>> From: Arınç ÜNAL <arinc.unal@...nc9.com>
>>
>> The CPU_PORT bits represent the CPU port to trap frames to for the MT7530
>> switch. This switch traps frames received from a user port to the CPU port
>> set on the CPU_PORT bits, regardless of the affinity of the user port from
>> which the frames are received.
> 
> I think:
> 
> "On the MT7530, the CPU_PORT() field indicates which CPU port to trap
> frames to, regardless of the affinity of the inbound user port."
> 
> covers everything necessary in the first paragraph? Sorry to be a pain
> about this, but commit logs should be understandable.

Sounds good to me.

> 
>> When multiple CPU ports are being used, the trapped frames won't be
>> received when the DSA conduit interface, which the frames are supposed to
>> be trapped to, is down because it's not affine to any user port. This
>> requires the DSA conduit interface to be manually set up for the trapped
>> frames to be received.
> 
> "When multiple CPU ports are in use, if the DSA conduit interface is
> down, trapped frames won't be passed to the conduit interface."

Ok.

> 
>> To fix this, implement ds->ops->master_state_change() on this subdriver and
>> set the CPU_PORT bits to the CPU port which the DSA conduit interface its
> 
> ... "to the first CPU port" - isn't that what the code is doing with
> __ffs(priv->active_cpu_ports)? You're giving priority to the lowest
> numbered port, and I think that should be stated in the commit message.

Will do.

Arınç