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Date:   Mon, 4 Jan 2021 18:31:05 +0100
From:   Andrew Lunn <andrew@lunn.ch>
To:     Ioana Ciornei <ioana.ciornei@nxp.com>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
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        <linux-renesas-soc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [RFC] net: phy: Fix reboot crash if CONFIG_IP_PNP is not
 set
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> The basic rules here should be, if the MDIO bus is registered, it is
> usable. There are things like PHY statistics, HWMON temperature
> sensors, etc, DSA switches, all which have a life cycle separate to
> the interface being up.

[Goes and looks at the code]

Yes, this is runtime PM which is broken.

sh_mdio_init() needs to wrap the mdp->mii_bus->read and
mdp->mii_bus->write calls with calls to

pm_runtime_get_sync(&mdp->pdev->dev);

and

pm_runtime_put_sync(&mdp->pdev->dev);

The KSZ8041RNLI supports statistics, which ethtool --phy-stats can
read, and these will also going to cause problems.

      Andrew