linux-kernel - Re: [PATCH net-next v2 4/6] net: mdio: scan bus based on bus capabilities for C22 and C45

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Date:   Sat, 11 Mar 2023 18:32:54 +0100
From:   Klaus Kudielka <klaus.kudielka@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Michael Walle <michael@...le.cc>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Felix Fietkau <nbd@....name>,
        John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Bryan Whitehead <bryan.whitehead@...rochip.com>,
        UNGLinuxDriver@...rochip.com,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-aspeed@...ts.ozlabs.org,
        Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH net-next v2 4/6] net: mdio: scan bus based on bus
 capabilities for C22 and C45

On Sat, 2023-03-11 at 17:11 +0100, Klaus Kudielka wrote:
> On Sat, 2023-03-11 at 16:39 +0100, Andrew Lunn wrote:
> 
> > If there is no DT node, by default, all 32 addresses on the bus are
> > scanned. However, DSA makes another assumption. There is a one to one
> > mapping between port number and PHY address on the MDIO bus. Port 0
> > uses MDIO address 0. Port 7 uses MDIO address 7 etc. If you have an 8
> > port switch, there is no point scanning addresses 8 to 31, they will
> > never be used.
> > 
> > The mdio bus structure has a member phy_mask. This is a bitmap. If bit
> > N is set, address N is not scanned. So i suggest you extend
> > mv88e6xxx_mdio_register() to set phy_mask based on
> > mv88e6xxx_num_ports(chip).
> > 
> 
> What you are proposing here would not show any improvement on the
> Omnia, as only the 6 ports would be scanned - right? 
> 

Well, maybe I misunderstood the argument with DT completely, so I gave it a try:

--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -3797,6 +3797,7 @@ static int mv88e6xxx_mdio_register(struct mv88e6xxx_chip *chip,
        bus->read_c45 = mv88e6xxx_mdio_read_c45;
        bus->write_c45 = mv88e6xxx_mdio_write_c45;
        bus->parent = chip->dev;
+       bus->phy_mask = GENMASK(31, mv88e6xxx_num_ports(chip));
 
        if (!external) {
                err = mv88e6xxx_g2_irq_mdio_setup(chip, bus);

> 

Now THAT one makes a difference! With this on top, I'm back at normal boot time!
I hope this is what you had in mind?

Best regards, Klaus