netdev - Re: [RFC PATCH net] net: phy: fix the issue that netif always links up after resuming

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Date:   Thu, 29 Nov 2018 16:37:48 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net] net: phy: fix the issue that netif always links
 up after resuming



On 11/29/2018 2:47 PM, Heiner Kallweit wrote:
> On 29.11.2018 09:12, Kunihiko Hayashi wrote:
>> Even though the link is down before entering hibernation,
>> there is an issue that the network interface always links up after resuming
>> from hibernation.
>>
>> The phydev->state is PHY_READY before enabling the network interface, so
>> the link is down. After resuming from hibernation, the phydev->state is
>> forcibly set to PHY_UP in mdio_bus_phy_restore(), and the link becomes up.
>>
>> This patch expects to solve the issue by changing phydev->state to PHY_UP
>> only when the link is up.
>>
>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
>> ---
>>  drivers/net/phy/phy_device.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>> index ab33d17..d5bba0f 100644
>> --- a/drivers/net/phy/phy_device.c
>> +++ b/drivers/net/phy/phy_device.c
>> @@ -309,8 +309,10 @@ static int mdio_bus_phy_restore(struct device *dev)
>>  		return ret;
>>  
>>  	/* The PHY needs to renegotiate. */
>> -	phydev->link = 0;
>> -	phydev->state = PHY_UP;
>> +	if (phydev->link) {
>> +		phydev->link = 0;
>> +		phydev->state = PHY_UP;
>> +	}
>>  
> Thanks for reporting. I agree that it isn't right to unconditionally set
> PHY_UP, because we don't know whether the PHY was started before
> hibernation. However I don't think using phydev->link as criteria is
> right. Example would be: PHY was started before hibernation, but w/o link.
> In this case we want to set PHY_UP to start an aneg, because a cable may
> have been plugged in whilst system was sleeping.
> 
> So I think, similar to phy_stop_machine, we should use state >= UP and
> state != HALTED as criteria, and also phy_start_machine() would need to
> be called only if this criteria is met.
> 
> It may make sense to add a helper for checking whether PHY is in a
> started state (>=UP && !=HALTED), because we need this in more than
> one place.

Agreed, that would make sense.
-- 
Florian