netdev - Re: [PATCH net 2/2] net: phy: fix WoL handling when suspending the PHY

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Message-ID: <4b3089bc-cd91-7a1f-b1bc-6d87fcb9fc1f@gmail.com>
Date:   Mon, 24 Sep 2018 21:56:31 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net 2/2] net: phy: fix WoL handling when suspending the
 PHY

On 24.09.2018 20:21, Florian Fainelli wrote:
> On 09/24/2018 11:11 AM, Heiner Kallweit wrote:
>> Core of the problem is that phy_suspend() suspends the PHY when it
>> should not because of WoL. phy_suspend() checks for WoL already, but
>> this works only if the PHY driver handles WoL (what is rarely the case).
>> Typically WoL is handled by the MAC driver.
>>
>> This patch uses new member wol_enabled of struct net_device as
>> additional criteria in the check when not to suspend the PHY because
>> of WoL.
>>
>> Last but not least change phy_detach() to call phy_suspend() before
>> attached_dev is set to NULL. phy_suspend() accesses attached_dev
>> when checking whether the MAC driver activated WoL.
> 
> Looks fine to me, just a few nits/questions down below:
> 
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> 
>>
>> Fixes: f1e911d5d0df ("r8169: add basic phylib support")
>> Fixes: e8cfd9d6c772 ("net: phy: call state machine synchronously in phy_stop")
>> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
>> ---
>>  drivers/net/phy/phy_device.c | 12 +++++++++---
>>  1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>> index af64a9320..6c0195e53 100644
>> --- a/drivers/net/phy/phy_device.c
>> +++ b/drivers/net/phy/phy_device.c
>> @@ -93,7 +93,12 @@ static bool mdio_bus_phy_may_suspend(struct phy_device *phydev)
>>  	if (!netdev)
>>  		return !phydev->suspended;
>>  
>> -	/* Don't suspend PHY if the attached netdev parent may wakeup.
>> +	if (netdev->wol_enabled)
>> +		return false;
>> +
>> +	/* As lang as not all affected network drivers support the
>> +	 * wol_enabled flag, let's check for hints that WoL is enabled.
> 
> Typo: as long (sorry for being that nitpicky).
> 
>> +	 * Don't suspend PHY if the attached netdev parent may wakeup.
>>  	 * The parent may point to a PCI device, as in tg3 driver.
>>  	 */
>>  	if (netdev->dev.parent && device_may_wakeup(netdev->dev.parent))
>> @@ -1132,9 +1137,9 @@ void phy_detach(struct phy_device *phydev)
>>  		sysfs_remove_link(&dev->dev.kobj, "phydev");
>>  		sysfs_remove_link(&phydev->mdio.dev.kobj, "attached_dev");
>>  	}
>> +	phy_suspend(phydev);
>>  	phydev->attached_dev->phydev = NULL;
>>  	phydev->attached_dev = NULL;
>> -	phy_suspend(phydev);
>>  	phydev->phylink = NULL;
>>  
>>  	phy_led_triggers_unregister(phydev);
>> @@ -1168,12 +1173,13 @@ EXPORT_SYMBOL(phy_detach);
>>  int phy_suspend(struct phy_device *phydev)
>>  {
>>  	struct phy_driver *phydrv = to_phy_driver(phydev->mdio.dev.driver);
>> +	struct net_device *netdev = phydev->attached_dev;
>>  	struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
>>  	int ret = 0;
>>  
>>  	/* If the device has WOL enabled, we cannot suspend the PHY */
>>  	phy_ethtool_get_wol(phydev, &wol);
>> -	if (wol.wolopts)
>> +	if (wol.wolopts || (netdev && netdev->wol_enabled))
> 
> Since you moved the phydev->attached_dev assignment to be after
> phy_suspend(), do you really need to check for netdev here? Is there
> another code path you found that might be running phy_suspend() with a
> disconnected PHY? Not a problem per-se, just wondering.
> 
There's a call to phy_suspend() in the phylib state machine and I'm
not sure we can guarantee that a netdevice is attached.
Because phy_suspend() is exported anybody can use it, correct or
incorrect. Therefore I'd say core functions better should play safe.