linux-kernel - Re: [PATCH net v4 1/7] net: dsa: mt7530: fix trapping frames with multiple CPU ports on MT7531

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Message-ID: <1e737fe9-6a2e-225b-9c0f-9a069e8fd4bc@arinc9.com>
Date:   Wed, 14 Jun 2023 23:56:44 +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>,
        Russell King <linux@...linux.org.uk>,
        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 1/7] net: dsa: mt7530: fix trapping frames with
 multiple CPU ports on MT7531

On 14.06.2023 22:43, Vladimir Oltean wrote:
> On Mon, Jun 12, 2023 at 10:59:39AM +0300, arinc9.unal@...il.com wrote:
>> From: Arınç ÜNAL <arinc.unal@...nc9.com>
>>
>> Every bit of the CPU port bitmap for MT7531 and the switch on the MT7988
>> SoC represents a CPU port to trap frames to. These switches trap frames
>> received from a user port to the CPU port that is affine to the user port
>> from which the frames are received.
>>
>> Currently, only the bit that corresponds to the first found CPU port is set
>> on the bitmap. When multiple CPU ports are being used, the trapped frames
>> from the user ports not affine to the first CPU port will be dropped as the
>> other CPU port is not set on the bitmap. The switch on the MT7988 SoC is
>> not affected as there's only one port to be used as a CPU port.
>>
>> To fix this, introduce the MT7531_CPU_PMAP macro to individually set the
>> bits of the CPU port bitmap. Set the CPU port bitmap for MT7531 and the
>> switch on the MT7988 SoC on mt753x_cpu_port_enable() which runs on a loop
>> for each CPU port.
>>
>> Add a comment to explain frame trapping for these switches.
>>
>> According to the document MT7531 Reference Manual for Development Board
>> v1.0, the MT7531_CPU_PMAP bits are unset after reset so no need to clear it
>> beforehand. Since there's currently no public document for the switch on
>> the MT7988 SoC, I assume this is also the case for this switch.
>>
>> Fixes: c288575f7810 ("net: dsa: mt7530: Add the support of MT7531 switch")
>> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
>> ---
> 
> Would you agree that this is just preparatory work for change "net: dsa:
> introduce preferred_default_local_cpu_port and use on MT7530" and not a
> fix to an existing problem in the code base?

Makes sense. Pre-preferred_default_local_cpu_port patch, there isn't a 
case where there's a user port affine to a CPU port that is not enabled 
on the CPU port bitmap. So yeah, this is just preparatory work for "net: 
dsa: introduce preferred_default_local_cpu_port and use on MT7530".

So how do I change the patch to reflect this?

Arınç