netdev - Re: [PATCH net] usbnet: smsc95xx: Fix deadlock on runtime resume

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Date:   Wed, 27 Apr 2022 17:45:01 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Steve Glendinning <steve.glendinning@...well.net>,
        UNGLinuxDriver@...rochip.com, Oliver Neukum <oneukum@...e.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org, Andre Edich <andre.edich@...rochip.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Martyn Welch <martyn.welch@...labora.com>,
        Gabriel Hojda <ghojda@...urs.ro>,
        Christoph Fritz <chf.fritz@...glemail.com>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH net] usbnet: smsc95xx: Fix deadlock on runtime resume

On Wed, Apr 27, 2022 at 05:24:50PM +0200, Andrew Lunn wrote:
> You have looked at this code, tried a few different things, so this is
> probably a dumb question.
> 
> Do you actually need to call phy_init_hw()?

I should add that the PHY register state may not be preserved on
runtime PM if woken via the ->reset_resume hook and I believe
that's the case when phy_init_hw() is necessary.

smsc95xx_suspend() currently accesses PHY registers behind the
PHY driver's back to enable Energy Detect Powerdown and it
uses smsc95xx_mdio_write_nopm() for that, hence that doesn't
deadlock *currently*, but the code should be moved to the PHY
driver, and then it will.

Thanks,

Lukas