linux-kernel - Re: [RFC PATCH net v3] net: phy: Fix the issue that netif always links up after resuming

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Message-ID: <a4bec1b7-1899-591a-c3b6-599e3730e2c1@gmail.com>
Date:   Mon, 17 Dec 2018 19:43:31 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net v3] net: phy: Fix the issue that netif always
 links up after resuming

On 17.12.2018 19:41, Heiner Kallweit wrote:
> On 17.12.2018 07:41, Kunihiko Hayashi wrote:
>> Hi,
>>
>> Gentle ping...
>> Are there any comments about changes since v2?
>>
>> v2: https://www.spinics.net/lists/netdev/msg536926.html
>>
>> Thank you,
>>
>> On Mon, 3 Dec 2018 17:22:29 +0900 <hayashi.kunihiko@...ionext.com> 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 adds a new convenient function to check whether the PHY is in
>>> a started state, and expects to solve the issue by changing phydev->state
>>> to PHY_UP and calling phy_start_machine() only when the PHY is started.
>>>
> This convenience function and the related change to phy_stop() are part of
> the following already and don't need to be part of your patch.
> https://patchwork.ozlabs.org/patch/1014171/
> 
>>> Suggested-by: Heiner Kallweit <hkallweit1@...il.com>
>>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
>>> ---
>>>
>>> Changes since v2:
>>>  - add mutex lock/unlock for changing phydev->state
>>>  - check whether the mutex is locked in phy_is_started()
>>>  
>>> Changes since v1:
>>>  - introduce a new helper function phy_is_started() and use it instead of
>>>    checking link status
>>>  - replace checking phydev->state with phy_is_started() in
>>>    phy_stop_machine()
>>>
>>> drivers/net/phy/phy.c        |  2 +-
>>>  drivers/net/phy/phy_device.c | 12 +++++++++---
>>>  include/linux/phy.h          | 13 +++++++++++++
>>>  3 files changed, 23 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
>>> index 1d73ac3..f484d03 100644
>>> --- a/drivers/net/phy/phy.c
>>> +++ b/drivers/net/phy/phy.c
>>> @@ -670,7 +670,7 @@ void phy_stop_machine(struct phy_device *phydev)
>>>  	cancel_delayed_work_sync(&phydev->state_queue);
>>>  
>>>  	mutex_lock(&phydev->lock);
>>> -	if (phydev->state > PHY_UP && phydev->state != PHY_HALTED)
>>> +	if (phy_is_started(phydev))
>>>  		phydev->state = PHY_UP;
> 
> I'm wondering whether we need to do this. If the PHY is attached,
> then mdio_bus_phy_suspend() calls phy_stop_machine() which does
> exactly the same. If the PHY is not attached, then we don't have
> to do anything. Therefore I think we just have to do the same as
> in mdio_bus_phy_resume():
> 
> if (phydev->attached_dev && phydev->adjust_link)
> 	phy_start_machine(phydev);
> 
> Can you test this?
> 
Sorry for the confusion, this comment is related to the next part
of your patch.

>>>  	mutex_unlock(&phydev->lock);
>>>  }
>>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>>> index ab33d17..4897d24 100644
>>> --- a/drivers/net/phy/phy_device.c
>>> +++ b/drivers/net/phy/phy_device.c
>>> @@ -309,10 +309,16 @@ static int mdio_bus_phy_restore(struct device *dev)
>>>  		return ret;
>>>  
>>>  	/* The PHY needs to renegotiate. */
>>> -	phydev->link = 0;
>>> -	phydev->state = PHY_UP;
>>> +	mutex_lock(&phydev->lock);
>>> +	if (phy_is_started(phydev)) {
>>> +		phydev->state = PHY_UP;
>>> +		mutex_unlock(&phydev->lock);
>>> +		phydev->link = 0;
>>> +		phy_start_machine(phydev);
>>> +	} else {
>>> +		mutex_unlock(&phydev->lock);
>>> +	}
>>>  
>>> -	phy_start_machine(phydev);
>>>  
>>>  	return 0;
>>>  }
>>> diff --git a/include/linux/phy.h b/include/linux/phy.h
>>> index 3ea87f7..dd21537 100644
>>> --- a/include/linux/phy.h
>>> +++ b/include/linux/phy.h
>>> @@ -898,6 +898,19 @@ static inline bool phy_is_pseudo_fixed_link(struct phy_device *phydev)
>>>  }
>>>  
>>>  /**
>>> + * phy_is_started - Convenience function for testing whether a PHY is in
>>> + * a started state
>>> + * @phydev: the phy_device struct
>>> + *
>>> + * The caller must have taken the phy_device mutex lock.
>>> + */
>>> +static inline bool phy_is_started(struct phy_device *phydev)
>>> +{
>>> +	WARN_ON(!mutex_is_locked(&phydev->lock));
>>> +	return phydev->state >= PHY_UP && phydev->state != PHY_HALTED;
>>> +}
>>> +
>>> +/**
>>>   * phy_write_mmd - Convenience function for writing a register
>>>   * on an MMD on a given PHY.
>>>   * @phydev: The phy_device struct
>>> -- 
>>> 2.7.4
>>
>> ---
>> Best Regards,
>> Kunihiko Hayashi
>>
>>
>>
>