netdev - Re: powering off phys on 'ip link set down'

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Message-ID: <b340593a-c28f-5bcf-4559-bbc23a462972@prevas.dk>
Date:   Thu, 27 Aug 2020 13:46:31 +0200
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Network Development <netdev@...r.kernel.org>
Cc:     Lasse Klok Mikkelsen <Lasse.Klok@...vas.se>
Subject: Re: powering off phys on 'ip link set down'

On 27/08/2020 13.14, Heiner Kallweit wrote:
> On 27.08.2020 13:00, Rasmus Villemoes wrote:
>> On 27/08/2020 12.29, Heiner Kallweit wrote:
>>> On 27.08.2020 12:08, Rasmus Villemoes wrote:
>>>> Hi,
>>>>
>>>> We have a requirement that when an interface is taken down
>>>> administratively, the phy should be powered off. That also works when
>>>> the interface has link when the 'ip link set down ...' is run. But if
>>>> there's no cable plugged in, the phy stays powered on (as can be seen
>>>> both using phytool, and from the fact that a peer gets carrier once a
>>>> cable is later plugged in).
>>>>
>>>> Is this expected behaviour? Driver/device dependent? Can we do anything
>>>> to force the phy off?

> 
> Maybe your question refers to something that was changed in 5.4 with
> the following commit:
> 95fb8bb3181b ("net: phy: force phy suspend when calling phy_stop")
> 

This is a 4.19-rt kernel, and yes, cherry-picking that commit does make
things work as expected (and required). Thanks a lot, Heiner!

Rasmus