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

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Date:   Wed, 14 Jun 2023 22:43:30 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     arinc9.unal@...il.com
Cc:     Arınç ÜNAL <arinc.unal@...nc9.com>,
        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 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?