linux-kernel - Re: e1000/ICH8LAN weirdness - no ethtool link until initially forced up

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Date:	Tue, 07 Nov 2006 14:32:32 -0800
From:	Auke Kok <auke-jan.h.kok@...el.com>
To:	"Robin H. Johnson" <robbat2@...too.org>
CC:	Auke Kok <auke-jan.h.kok@...el.com>, Pavel Machek <pavel@....cz>,
	linux-kernel@...r.kernel.org
Subject: Re: e1000/ICH8LAN weirdness - no ethtool link until initially forced
 up

Robin H. Johnson wrote:
> On Tue, Nov 07, 2006 at 07:51:22AM -0800, Auke Kok wrote:
>>> I think you should cc e1000 maintainers, and perhaps provide a patch....
>> I've read it and not come up with an answer due to some other issues at 
>> hand. E1000 hardware works differently and this has been asked before, but 
>> the cards itself are in low power state when down. Changing this to bring 
>> up the link would make the card start to consume lots more power, which 
>> would automatically suck enormously for anyone using a laptop.
>>
>> Unfortunately, we have no way to distinguish directly between mobile and 
>> non-mobile adapters, since they are usually the same.
>>
>> Your application should really `ifconfig up` the device before checking for 
>> link.
> Actually pushing the link up in userspace doesn't specifically help my
> applications, as I care about actual link status (as reported by
> ethtool).

technically the link is already up if the cable is inserted and connected. doing an 
`ifconfig up` doesn't change that. If the link is down then this powers up the PHY so we 
can read the link status.

> Is there no way to keep the link status correct (within 0.5 seconds),
> without bringing the card to full power? Maybe a timer that fires a
> proper check (with the power implications).

no, not that I know of.

> Would a patch that adds a modparam (not enabled by default) running the
> behavior I'm after, be acceptable, so the e1000 driver can act identical
> to all of the other drivers?

I bet that all drivers work fine if you `ifconfig up` them. What happens if other NIC 
drivers implement similar powersaving methods and start working the same?

Cheers,

Auke

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