linux-kernel - Re: [PATCH v2 0/5] net: phy: Ethernet PHY powerdown optimization

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Date:	Tue, 04 Feb 2014 20:38:22 +0100
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	David Miller <davem@...emloft.net>
CC:	f.fainelli@...il.com, mugunthanvnm@...com, netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v2 0/5] net: phy: Ethernet PHY powerdown optimization

On 12/17/2013 08:43 PM, David Miller wrote:
> From: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
> Date: Fri, 13 Dec 2013 10:20:24 +0100
>
>> This is v2 of the ethernet PHY power optimization patches to reduce
>> power consumption of network PHYs with link that are either unused or
>> the corresponding netdev is down.
>>
>> Compared to the last version, this patch set drops a patch to disable
>> unused PHYs after late initcall, as it is not compatible with a modular
>> mdio bus [1]. I'll investigate different ways to have a modular mdio bus
>> driver get notified when driver loading is done.
>>
>> Again, a branch with v2 applied to v3.13-rc2 can also be found at
>> https://github.com/shesselba/linux-dove.git topic/ethphy-power-v2
>>
>> [1] http://www.spinics.net/lists/arm-kernel/msg293028.html
>
> Series applied, thanks.
>

David, Mungunthan, Florian,

as expected the above patches create a Linux to bootloader dependency
that surfaces dumb bootloaders not initializing PHYs correctly.

Andrew has a Kirkwood based board that does not power-up and restart
auto-negotiation on the powered down PHY after a warm restart. While
this specific bootloader allows a soft-workaround by issuing the
required PHY writes before accessing the interface, others may not.

I think we should allow the user to soft-disable the automatic
power-down of PHYs, i.e. by exploiting a kernel parameter.

Do you have any preference for naming it? My call would be something
like libphy.suspend_halted = [0,1] with 1 being the default.

Sebastian

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