Re: [net-next: PATCH v3 6/8] net: core: switch to fwnode_find_net_device_by_node()

From: Vladimir Oltean <olteanv@gmail.com>
To: Marcin Wojtas <mw@semihalf.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
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	Sean Wang <sean.wang@mediatek.com>,
	Landen Chao <Landen.Chao@mediatek.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	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>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	Heiner Kallweit <hkallweit1@gmail.com>,
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	Tomasz Nowicki <tn@semihalf.com>,
	Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>,
	upstream@semihalf.com
Subject: Re: [net-next: PATCH v3 6/8] net: core: switch to fwnode_find_net_device_by_node()
Date: Wed, 27 Jul 2022 19:38:48 +0300	[thread overview]
Message-ID: <20220727163848.f4e2b263zz3vl2hc@skbuf> (raw)
In-Reply-To: <CAPv3WKc88KQN=athEqBg=Z5Bd1SC3QSOPZpDH7dfuYGHhR+oVg@mail.gmail.com>

On Wed, Jul 27, 2022 at 05:18:16PM +0200, Marcin Wojtas wrote:
> Do you mean a situation analogous to what I addressed in:
> [net-next: PATCH v3 4/8] net: mvpp2: initialize port fwnode pointer
> ?

Not sure if "analogous" is the right word. My estimation is that the
overwhelmingly vast majority of DSA masters can be found by DSA simply
due to the SET_NETDEV_DEV() call that the Ethernet drivers need to make
anyway.  I see that mvpp2 also needed commit c4053ef32208 ("net: mvpp2:
initialize port of_node pointer"), but that isn't needed in general, and
I can't tell you exactly why it is needed there, I don't know enough
about the mvpp2 driver.

> I found indeed a couple of drivers that may require a similar change
> (e.g. dpaa2).

There I can tell you why the dpaa2-mac code mangles with net_dev->dev.of_node,
but I'd rather not go into an explanation that essentially doesn't matter.
The point is that you'd be mistaken to think that only the drivers which
touch the net device's ->dev->of_node are the ones that need updating
for your series to not cause regressions.

> IMO we have 2 options:
> - update these drivers
> - add some kind of fallback? If yes, I am wondering about an elegant
> solution - maybe add an extra check inside
> fwnode_find_parent_dev_match?
> 
> What would you suggest?

Fixing fwnode_find_parent_dev_match(), of course. This change broke DSA
on my LS1028A system (master in drivers/net/ethernet/freescale/enetc/)
and LS1021A (master in drivers/net/ethernet/freescale/gianfar.c).