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

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Date:   Mon, 17 Dec 2018 19:41:34 +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 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?

>>  	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
> 
> 
>