netdev - Re: Potential issue with f5e64032a799 "net: phy: fix resume handling"

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Message-ID: <20180203201748.GN16818@lunn.ch>
Date:   Sat, 3 Feb 2018 21:17:48 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Russell King <rmk+kernel@...linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Potential issue with f5e64032a799 "net: phy: fix resume handling"

On Sat, Feb 03, 2018 at 05:41:54PM +0100, Heiner Kallweit wrote:
> This commit forces callers of phy_resume() and phy_suspend() to hold
> mutex phydev->lock. This was done for calls to phy_resume() and
> phy_suspend() in phylib, however there are more callers in network
> drivers. I'd assume that these other calls issue a warning now
> because of the lock not being held.
> So is there something I miss or would this have to be fixed?

Hi Heiner

This is a good point.

Yes, it looks like some fixes are needed. But what exactly?

The phy state machine will suspend and resume the phy is you call
phy_stop() and phy_start() in the MAC suspend and resume functions.

A few examples:

tc35815_suspend(), ravb_suspend() via ravb_close(), sh_eth_suspend()
via sh_eth_close(), fec_suspend(), mpc52xx_fec_of_suspend() via
mpc52xx_fec_close(), ucc_geth_suspend(), etc...

So i suspect those drivers which call phy_suspend()/phy_resume()
should really be modified to call phy_stop()/phy_start().

hns_nic_config_phy_loopback() is just funky, and probably needs the
help of the hns guys to fix.

dsa_slave_suspend() already does a phy_stop(), so the phy_suspend()
can be removed.

The comments in lpc_eth_open() suggest the phy_resume() is needed, so
locks should be added. socfpga_dwmac_resume() seems to be the same.

    Andrew