netdev - Re: Choose a default DSA CPU port

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Date:   Wed, 22 Feb 2023 21:39:51 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Frank Wunderlich <frank-w@...lic-files.de>
Cc:     Arınç ÜNAL <arinc.unal@...nc9.com>,
        netdev <netdev@...r.kernel.org>, erkin.bozoglu@...ont.com,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>
Subject: Re: Choose a default DSA CPU port

On Wed, Feb 22, 2023 at 06:17:42PM +0100, Frank Wunderlich wrote:
> Hi
> 
> thanks vladimir for the Patch, seems to work so far...
> system now says dsa-ports are routed over eth0 and ethtool stats say it too.

Unrelated to the perf degradation reported on mt7530, just something I
noticed.

When using 2 CPU ports in the device tree and selecting port 6 by
default, mt7531 will break, because it will send STP packets to port 5:

	/* BPDU to CPU port */
	dsa_switch_for_each_cpu_port(cpu_dp, ds) {
		mt7530_rmw(priv, MT7531_CFC, MT7531_CPU_PMAP_MASK,
			   BIT(cpu_dp->index));
		break; // breaking means that MT7531_CPU_PMAP_MASK will remain at BIT(5)
	}

Someone needs to go with a fery fine comb through the driver and analyze
the assumptions which are being made about which CPU port is active and
which one isn't.