linux-kernel - Re: radeonfb i2c regression post-2.6.18.

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Message-ID: <20071124102945.0d6f9934@hyperion.delvare>
Date:	Sat, 24 Nov 2007 10:29:45 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	benh@...nel.crashing.org
Cc:	Michael Buesch <mb@...sch.de>,
	Roger Leigh <rleigh@...nlatter.ukfsn.org>,
	linux-kernel@...r.kernel.org, Dennis Munsie <dmunsie@...ropia.com>
Subject: Re: radeonfb i2c regression post-2.6.18.

On Sat, 24 Nov 2007 12:11:04 +1100, Benjamin Herrenschmidt wrote:
> 
> On Fri, 2007-11-23 at 23:29 +0100, Jean Delvare wrote:
> > On Fri, 23 Nov 2007 17:00:52 +0100, Michael Buesch wrote:
> > > This patch fixes my crash problem.
> > 
> > Out of curiosity, what kind of crash was it? I admit that I can't see
> > how the code could crash.
> 
> Really sneaky... apparently, keeping the i2c lines asserted on his
> laptop model would drain enough current through the pullups (or the
> chip) that the temperature will raise significantly, causing a thermal
> shutdown if the machine was already warm.
> 
> A bit scary... looks to me that a pullup is a bit too weak somewhere on
> the motherboard.
> 
> That also means that this fix should reduce power consumption on the
> battery significantly on those machines as it must take quite a bit of
> power to increase the temperature that significantly (either that, or
> the heating part sits just next to the sensor).

Wow, nasty. Then my patch really needs to go to Linus at the earliest.

Thanks,
-- 
Jean Delvare
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