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

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Message-Id: <20181130153842.31FF.4A936039@socionext.com>
Date:   Fri, 30 Nov 2018 15:38:43 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>, 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

Hi Heiner,

On Fri, 30 Nov 2018 07:20:27 +0100 <hkallweit1@...il.com> wrote:

> On 30.11.2018 05:37, Kunihiko Hayashi wrote:
> > Hi Heiner Florian,
> > 
> > Thank you for your comments.
> > 
> > On Thu, 29 Nov 2018 16:37:48 -0800 <f.fainelli@...il.com> wrote:
> > 
> >>
> >>
> >> 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.
> > 
> > Indeed. I didn't consider the case that the PHY was started but a cable was
> > unplugged before hibernation.
> > 
> >>> 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.
> > 
> > I agree, too.
> > I'll try this in v2 patch that changes the PHY state to PHY_UP and calls
> > phy_start_machine(), only when the PHY was started before hibernation.
> > If I understand correctly, it will be like that:
> > 
> > 	phydev->link = 0;
> Even this may go into the if clause. If PHY isn't started then
> phydev->link should be 0 anyway.

Yes. To clarify more, this will go into the if clause. 

> 
> > 	if (phy_is_started(phydev)) {
> > 		phydev->state = PHY_UP;
> > 		phy_start_machine(phydev);
> > 	}
> > 
> Yes, this is what was meant. Thanks.

Thank you,

---
Best Regards,
Kunihiko Hayashi