netdev - Re: [PATCH net-next 0/5] net: phy: C45-over-C22 access

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Date:   Tue, 24 Jan 2023 22:20:33 +0100
From:   Michael Walle <michael@...le.cc>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Marek Behún <kabel@...nel.org>,
        Xu Liang <lxu@...linear.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 0/5] net: phy: C45-over-C22 access

Am 2023-01-24 22:03, schrieb Andrew Lunn:
>> Btw. for the DT case, it seems we need yet another property
>> to indicate broken MDIO busses.
> 
> I would prefer to avoid that. I would suggest you do what i did for
> the none DT case. First probe using C22 for all devices known in DT.
> Then call mdiobus_prevent_c45_scan() which will determine if any of
> the found devices are FUBAR and will break C45. Then do a second probe
> using C45 and/or C45 over C22 for those devices in DT with the c45
> compatible.

I tried that yesterday. Have a look at of_mdiobus_register() [1].
There the device tree is walked and each PHY with a reg property
is probed. Afterwards, if there was a node without a reg property,
the bus is scanned for the missing PHYs. If we would just probe c22
first, the order of the auto scanning might change, if there is a
c45 phy in between two c22 phys. I was thinking to just ignore the
case that the autoscan would discover a broken PHY.

  (1) scan c22
  (2) scan c45 (maybe using c45-over-c22)
  (3) do the autoscan

-michael

[1] 
https://elixir.bootlin.com/linux/v6.2-rc5/source/drivers/net/mdio/of_mdio.c#L149



> 
> 	Andrew