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

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Date:   Fri, 6 Oct 2017 07:00:49 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Andrew Lunn <andrew@...n.ch>, <Woojung.Huh@...rochip.com>
CC:     <f.fainelli@...il.com>, <netdev@...r.kernel.org>, <afd@...com>
Subject: Re: [PATCH 2/3 v2] net: phy: DP83822 initial driver submission

Andrew

On 10/04/2017 06:53 PM, Andrew Lunn wrote:
> 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?
> 

The marvell driver does not take a lock and calls genphy_suspend/resume
so I am wondering if this driver needs to take a lock.

The at803x needs to take the lock because it does not call into the genphy
functions.

I will submit a new version with the lock removed.

Dan

>       Andrew
> 


-- 
------------------
Dan Murphy