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

From: Vladimir Oltean <olteanv@gmail.com>
To: "Arınç ÜNAL" <arinc.unal@arinc9.com>
Cc: Daniel Golle <daniel@makrotopia.org>,
	Landen Chao <Landen.Chao@mediatek.com>,
	DENG Qingfang <dqfext@gmail.com>,
	Sean Wang <sean.wang@mediatek.com>, Andrew Lunn <andrew@lunn.ch>,
	Florian Fainelli <f.fainelli@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	Russell King <linux@armlinux.org.uk>,
	Frank Wunderlich <frank-w@public-files.de>,
	Bartel Eerdekens <bartel.eerdekens@constell8.be>,
	mithat.guner@xeront.com, erkin.bozoglu@xeront.com,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH net v2 2/7] net: dsa: mt7530: fix trapping frames with multiple CPU ports on MT7530
Date: Tue, 13 Jun 2023 23:59:15 +0300	[thread overview]
Message-ID: <20230613205915.rmpuqq7ahmd7taeq@skbuf> (raw)
In-Reply-To: <4a2fb3ac-ccad-f56e-4951-e5a5cb80dd1b@arinc9.com>

On Tue, Jun 13, 2023 at 11:35:08PM +0300, Arınç ÜNAL wrote:
> On 13.06.2023 23:18, Vladimir Oltean wrote:
> > On Tue, Jun 13, 2023 at 08:58:33PM +0300, Arınç ÜNAL wrote:
> > > On 13.06.2023 20:39, Vladimir Oltean wrote:
> > > > 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.
> > > 
> > > Once "the patch that prefers port 6, I could easily find the exact name but
> > > your mail snipping makes it hard" is applied, this issue becomes redundant.
> > 
> > Ok. Well, you don't get bonus points for fixing a problem in 2 different
> > ways, once is enough :)
> 
> This is not the case here though.
> 
> This patch fixes an issue that can be stumbled upon in two ways. This is for
> when multiple CPU ports are defined on the devicetree.
> 
> As I explained to Russell, the first is the CPU_PORT field not matching the
> active CPU port.
> 
> The second is when port 5 becomes the only active CPU port. This can only
> happen with the changing the DSA conduit support.
> 
> The "prefer port 6" patch only prevents the first way from happening. The
> latter still can happen. But this feature doesn't exist yet. Hence why I
> think we should apply this series as-is (after some patch log changes) and
> backport it without this patch on kernels older than 5.18.
> 
> Arınç

I was following you until the last phrase. Why should we apply this series
as-is [ to net.git ], if this patch fixes a problem (the *only* problem in
lack of .port_change_master() support, aka for stable kernels) that is
already masked by a different patch targeted to net.git?

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