Message-ID: <024b696003d8403d62c45411c813058684e0418c.camel@gmail.com>
Subject: Re: [PATCH net-next v2 4/6] net: mdio: scan bus based on bus
 capabilities for C22 and C45
From:   Klaus Kudielka <klaus.kudielka@gmail.com>
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     Michael Walle <michael@walle.cc>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, Felix Fietkau <nbd@nbd.name>,
        John Crispin <john@phrozen.org>,
        Sean Wang <sean.wang@mediatek.com>,
        Mark Lee <Mark-MC.Lee@mediatek.com>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Bryan Whitehead <bryan.whitehead@microchip.com>,
        UNGLinuxDriver@microchip.com,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-aspeed@lists.ozlabs.org,
        Jesse Brandeburg <jesse.brandeburg@intel.com>
Date:   Sun, 12 Mar 2023 16:15:41 +0100
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On Sun, 2023-03-12 at 10:04 +0100, Klaus Kudielka wrote:
> On Sun, 2023-03-12 at 03:53 +0100, Andrew Lunn wrote:
> >=20
> > Correct. But their also should not of been any noticeable slow down,
> > because there should not be any additional scanning when everything is
> > described in DT. And the move of the MDIO bus registration from probe
> > to setup should actually make it faster than before.
> >=20
>=20
> But then, why *do* I see such a big difference on the Omnia?
>=20
> mdiobus_scan_bus_c45() takes:
> ~2.7 seconds without phy_mask patch
> ~0.2 seconds with phy_mask patch

Following up myself, the answer is in the call path
mv88e6xxx_mdios_register()
	 -> mv88e6xxx_mdio_register()
		-> of_mdiobus_register()

A child node "mdio" would be needed for the scan to be limited by
the device tree. And this one is *not* in armada-385-turris-omnia.dts.

My (incorrect) understanding was, the child node "ports" would trigger
that behaviour.

Best regards, Klaus