netdev - Re: 2.6.29-rc3: tg3 dead after resume

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Date:	Sat, 07 Feb 2009 14:26:06 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Parag Warudkar <parag.lkml@...il.com>,
	Matt Carlson <mcarlson@...adcom.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: 2.6.29-rc3: tg3 dead after resume

> 
> Here's a big hint: YOU DO NOT KNOW. YOU MUST NOT TURN OFF THE BRIDGE AT 
> SUSPEND TIME!

A quick catch up on old emails ....

A good reason not to turn bridges off is that behind bridges, you'll
find more than your "normal" PCI devices. You'll find system devices,
things like your motherboard GPIO & clock control, i2c controllers,
service processors, your PIC, etc... 

And your BIOS will need them. Your ACPI stuff will indirectly access
these things, for example to get the machine into actual suspend state
etc...

Disabling bridges is bad :-)

If they have to be disabled for power management purposes, then it's
likely that ACPI/BIOS itself will do it at the very last minute when
going into S3, and bring them back itself on the way back.

For embedded platforms who want to override that, they can always stick
a driver there or do it manually from a sysdev or platform code.

IE. I very very much doubt windows does anything to bridges, appart
-maybe- saving/restoring the standard window settings -just-in-case-
they got wiped out and the BIOS didn't restore them.

Ben.

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