netdev - Re: [PATCH RFC 3/7] net: phy: resume PHY only if needed in, mdio_bus_phy

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Date:   Wed, 14 Mar 2018 16:50:23 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC 3/7] net: phy: resume PHY only if needed in,
 mdio_bus_phy_suspend

On 03/14/2018 01:16 PM, Heiner Kallweit wrote:
> Currently the PHY is unconditionally resumed in mdio_bus_phy_suspend().
> In cases where the PHY was sleepinh before suspending or if somebody else
> takes care of resuming later, this is not needed and wastes energy.
> 
> Also start the state machine only if it's used by the driver (indicated
> by the adjust_link callback being defined).
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/net/phy/phy_device.c | 33 +++++++++++++++++++++++----------
>  1 file changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index a5691536f..c6fd79758 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -124,6 +124,18 @@ static bool phy_may_suspend(struct phy_device *phydev)
>  }
>  
>  #ifdef CONFIG_PM
> +
> +static bool mdio_bus_phy_needs_start(struct phy_device *phydev)
> +{
> +	bool start;

How about needs_start? This is uber nitpicking but it seems to be more
in line with what is being tested for here.

> +
> +	mutex_lock(&phydev->lock);
> +	start = phydev->state == PHY_UP && phydev->adjust_link;

You probably need to add an || phydev->phy_link_change here because that
is what PHYLINK uses, it does not register an adjust_link callback, but
would likely expect similar semantics. Even better, introduce a helper
function that tests for both to avoid possible issues...

> +	mutex_unlock(&phydev->lock);
> +
> +	return start;
> +}
> +
>  static int mdio_bus_phy_suspend(struct device *dev)
>  {
>  	struct phy_device *phydev = to_phy_device(dev);
> @@ -142,25 +154,25 @@ static int mdio_bus_phy_suspend(struct device *dev)
>  static int mdio_bus_phy_resume(struct device *dev)
>  {
>  	struct phy_device *phydev = to_phy_device(dev);
> -	int ret;
> +	int ret = 0;
>  
> -	ret = phy_resume(phydev);
> -	if (ret < 0)
> -		return ret;
> +	if (!phydev->attached_dev)
> +		return 0;
>  
> -	if (phydev->attached_dev && phydev->adjust_link)
> -		phy_start_machine(phydev);
> +	if (mdio_bus_phy_needs_start(phydev))
> +		phy_start(phydev);
> +	else if (!phydev->adjust_link)
> +		ret = phy_resume(phydev);

Humm, under which conditions can you not have phydev->attached_dev and
also not phydev->adjust_link being set? As mentioned earlier, you would
likely need to test for phy_link_change too here.

>  
> -	return 0;
> +	return ret;
>  }
>  
>  static int mdio_bus_phy_restore(struct device *dev)
>  {
>  	struct phy_device *phydev = to_phy_device(dev);
> -	struct net_device *netdev = phydev->attached_dev;
>  	int ret;
>  
> -	if (!netdev)
> +	if (!phydev->attached_dev)
>  		return 0;

That does not seem to be making any functional difference, so I would
just drop this for now.

>  
>  	ret = phy_init_hw(phydev);
> @@ -171,7 +183,8 @@ static int mdio_bus_phy_restore(struct device *dev)
>  	phydev->link = 0;
>  	phydev->state = PHY_UP;
>  
> -	phy_start_machine(phydev);
> +	if (mdio_bus_phy_needs_start(phydev))
> +		phy_start(phydev);
>  
>  	return 0;
>  }
> 


-- 
Florian