netdev - Re: drivers/of/of_mdio.c needs a small modification

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Message-ID: <20200828222846.GA2403519@lunn.ch>
Date:   Sat, 29 Aug 2020 00:28:46 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Adam Rudziński <adam.rudzinski@....net.pl>
Cc:     robh+dt@...nel.org, frowand.list@...il.com, f.fainelli@...il.com,
        netdev <netdev@...r.kernel.org>
Subject: Re: drivers/of/of_mdio.c needs a small modification

Hi Adam

> If kernel has to bring up two Ethernet interfaces, the processor has two
> peripherals with functionality of MACs (in i.MX6ULL these are Fast Ethernet
> Controllers, FECs), but uses a shared MDIO bus, then the kernel first probes
> one MAC, enables clock for its PHY, probes MDIO bus tryng to discover _all_
> PHYs, and then probes the second MAC, and enables clock for its PHY. The
> result is that the second PHY is still inactive during PHY discovery. Thus,
> one Ethernet interface is not functional.

What clock are you talking about? Do you have the FEC feeding a 50MHz
clock to the PHY? Each FEC providing its own clock to its own PHY? And
are you saying a PHY without its reference clock does not respond to
MDIO reads and hence the second PHY does not probe because it has no
reference clock?

	  Andrew