netdev - Re: smsc911x suspend/resume

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Message-ID: <20100208144951.GF28972@buzzloop.caiaq.de>
Date:	Mon, 8 Feb 2010 15:49:51 +0100
From:	Daniel Mack <daniel@...aq.de>
To:	Mike Rapoport <mike@...pulab.co.il>
Cc:	Steve Glendinning <steve.glendinning@...c.com>,
	netdev@...r.kernel.org,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: smsc911x suspend/resume

On Mon, Feb 08, 2010 at 04:42:25PM +0200, Mike Rapoport wrote:
> Daniel Mack wrote:
> > In fact the datasheet doesn't really state that, and the chip seems
> > to expect the power domains to remain switched on during suspend, and
> > all power switching is done internally. Also the table in "7.4 Power
> > Consumption (Device and System Components)" describes it like that.
> > 
> > So it all comes down to the question of how low-power you need to be,
> > and whether you need wake-on-lan or not. What's currently implemented is
> > D1, but adding support for D2 should be easy.
> 
> I did some brute force save/restore of smsc9220 registers and it seems
> to wake up now.
> The question now is how to make it in a "generic" way ...
> Thanks for the help anyway :)

Hmm, be careful about switching off power supplies that aren't supposed
to be switched off while others are still powered. You can easily
destroy hardware with that. Depending on how things are wired up
internally, voltages can leak from one unit block to the other. Maybe
Steve can can give a statement from official SMSC source about whether
it is safe to switch off VDD33A in this case.

Anyway, from what's written in the datasheet, I wouldn't dare just
blindly doing it.

Daniel
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