linux-kernel - Re: [PATCH net v2 2/7] net: dsa: mt7530: fix trapping frames with multiple CPU ports on MT7530

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Message-ID: <c838ed22-8bc0-9f99-ee9f-4f8dbaabb99a@arinc9.com>
Date:   Tue, 13 Jun 2023 21:46:42 +0300
From:   Arınç ÜNAL <arinc.unal@...nc9.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Vladimir Oltean <olteanv@...il.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>,
        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 v2 2/7] net: dsa: mt7530: fix trapping frames with
 multiple CPU ports on MT7530

On 13.06.2023 21:29, Russell King (Oracle) wrote:
> On Tue, Jun 13, 2023 at 08:58:33PM +0300, Arınç ÜNAL wrote:
>> On 13.06.2023 20:39, Vladimir Oltean wrote:
>>> On Tue, Jun 13, 2023 at 08:30:28PM +0300, Arınç ÜNAL wrote:
>>>> That fixes port 5 on certain variants of the MT7530 switch, as it was
>>>> already working on the other variants, which, in conclusion, fixes port 5 on
>>>> all MT7530 variants.
>>>
>>> Ok. I didn't pay enough attention to the commit message.
>>>
>>>> And no, trapping works. Having only CPU port 5 defined on the devicetree
>>>> will cause the CPU_PORT bits to be set to port 5. There's only a problem
>>>> when multiple CPU ports are defined.
>>>
>>> Got it. Then this is really not a problem, and the commit message frames
>>> it incorrectly.
>>
>> Actually this patch fixes the issue it describes. At the state of this
>> patch, when multiple CPU ports are defined, port 5 is the active CPU port,
>> CPU_PORT bits are set to port 6.
> 
> Maybe it's just me being dumb, but I keep finding things difficult to
> understand, such as the above paragraph.
> 
> It sounds like you're saying that _before_ this patch, port 5 is the
> active CPU port, but the CPU_PORT *FIELD* NOT BITS are set such that
> port 6 is the active CPU port. Therefore, things are broken, and this
> patch fixes it.

Yes, CPU_PORT field, and yes this patch fixes the issue by setting the 
field to 5 when multiple CPU ports are used. Because before this patch, 
the active CPU port is 5. The CPU_PORT field must match this.

> 
> Or are you saying that after this patch is applied, port 5 is the
> active CPU port, but the CPU_PORT *FIELD* is set to port 6. If that's
> true, then I've no idea what the hell is going on here because it
> seems to be senseless.

No, when the "prefer port 6" patch is applied, the active CPU port will 
be port 6.

The CPU_PORT field will always be set to 6, regardless of "net: dsa: 
mt7530: fix trapping frames with multiple CPU ports on MT7530". 
Therefore, the "prefer port 6" patch makes "net: dsa: mt7530: fix 
trapping frames with multiple CPU ports on MT7530" redundant.

"net: dsa: mt7530: fix trapping frames with multiple CPU ports on 
MT7530" becomes important after the changing the DSA conduit support is 
introduced.

> 
> I think at this point I just give up trying to understand what the
> hell these patches are trying to do - in my opinion, the commit
> messages are worded attrociously and incomprehensively.

If that's how you feel, you can tune in to v5 where I will address the 
patch logs.

Arınç