netdev - Re: [RFC PATCH net v2] net: phy: Fix the issue that netif always links up after resuming

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Date:   Fri, 30 Nov 2018 09:46:42 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net v2] net: phy: Fix the issue that netif always
 links up after resuming



On 11/30/2018 1:25 AM, 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 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.
> 
> Suggested-by: Heiner Kallweit <hkallweit1@...il.com>
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> ---
>  drivers/net/phy/phy.c        |  2 +-
>  drivers/net/phy/phy_device.c |  9 +++++----
>  include/linux/phy.h          | 10 ++++++++++
>  3 files changed, 16 insertions(+), 5 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;
>  	mutex_unlock(&phydev->lock);
>  }
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index ab33d17..2c39717 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -309,10 +309,11 @@ static int mdio_bus_phy_restore(struct device *dev)
>  		return ret;
>  
>  	/* The PHY needs to renegotiate. */
> -	phydev->link = 0;
> -	phydev->state = PHY_UP;
> -
> -	phy_start_machine(phydev);
> +	if (phy_is_started(phydev)) {
> +		phydev->link = 0;
> +		phydev->state = PHY_UP;
> +		phy_start_machine(phydev);
> +	}

Don't you need some of these steps to be performed under phydev->lock
being held? See comment below.

>  
>  	return 0;
>  }
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 3ea87f7..c194b45 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -898,6 +898,16 @@ 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
> + */
> +static inline bool phy_is_started(struct phy_device *phydev)
> +{

An assert with the phydev->lock mutex being held here would greatly
help, because otherwise this is possibly racy.

> +	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
> 

-- 
Florian