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

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Date: Mon, 12 Jun 2023 22:09:45 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
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>,
	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 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.

> 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."

> 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.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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