netdev - Re: [PATCH net-next v2 02/10] r8169: use phy_resume/phy

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Message-ID: <8fe5cd19-eeb6-1c51-4c4e-3d37f78ed16c@gmail.com>
Date:   Tue, 10 Jul 2018 23:56:00 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 02/10] r8169: use phy_resume/phy_suspend

On 10.07.2018 22:52, Andrew Lunn wrote:
>>> Why is it powered up, but not connected? Is it powered down before it
>>> is disconnected? Is it the bootloader which is powering it up?
>>>
>> Exactly, if the device is active when driver is loaded and the
>> interface isn't used and therefore not brought up, then, when runtime-
>> suspending, we face this situation.
> 
> Well, it is more complex than that. If the interface is not used, why
> bother even loading the MAC driver?
> 
> If you are trying to make a really low power system, the bootloader
> also needs to be involved. It needs to shut down anything it starts
> before handing over control the linux.
> 
> Another approach is to handle this in phylib. When the mdio bus is
> suspended, look for any PHYs which are not connected and power them
> down. The assumption being, any MAC driver using WoL via a PHY does
> not disconnect the PHY before suspending.
> 
Tricky part may be the differentiation between system- and runtime-
suspend. IIRC the MDIO bus doesn't have runtime pm ops (yet) and
most likely we would have to add them.

>     Andrew
>