netdev - Re: [PATCH 2/3 v2] net: phy: DP83822 initial driver submission

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Date:   Thu, 5 Oct 2017 01:53:07 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Woojung.Huh@...rochip.com
Cc:     dmurphy@...com, f.fainelli@...il.com, netdev@...r.kernel.org,
        afd@...com
Subject: Re: [PATCH 2/3 v2] net: phy: DP83822 initial driver submission

On Wed, Oct 04, 2017 at 10:44:36PM +0000, Woojung.Huh@...rochip.com wrote:
> > +static int dp83822_suspend(struct phy_device *phydev)
> > +{
> > +	int value;
> > +
> > +	mutex_lock(&phydev->lock);
> > +	value = phy_read_mmd(phydev, DP83822_DEVADDR,
> > MII_DP83822_WOL_CFG);
> > +	mutex_unlock(&phydev->lock);

> Would we need mutex to access phy_read_mmd()?
> phy_read_mmd() has mdio_lock for indirect access.

Hi Woojung

The mdio lock is not sufficient. It protects against two mdio
accesses. But here we need to protect against two phy operations.
There is a danger something else tries to access the phy during
suspend.

> > +	if (!(value & DP83822_WOL_EN))
> > +		genphy_suspend(phydev);

Releasing the lock before calling genphy_suspend() is not so nice.
Maybe add a version which assumes the lock has already been taken?

      Andrew