Date: Fri, 17 May 2013 22:18:19 +1000
From: Robert Norris <robn@opera.com>
To: Jean Delvare <khali@linux-fr.org>
Cc: Daniel Kurtz <djkurtz@chromium.org>, linux-kernel@vger.kernel.org,
        Linux I2C <linux-i2c@vger.kernel.org>
Subject: Re: PROBLEM: modprobe hang at startup (3.8.x, 3.9.x, IBM x3550)
Message-ID: <20130517121819.GA3165@pyro.melbourne.osa>
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On Fri, May 17, 2013 at 10:36:22AM +0200, Jean Delvare wrote:
> IPMI is still likely to access the SMBus controller. If there's a BMC
> in the machine, it can also access the SMBus slave with its own
> controller. It would be good to rule this out by disabling IPMI
> completely, removing the BMC from the machine if it has one, and
> checking if it makes the issue go away or not.

This ended up being easier than I thought. The BMC can't be physically
removed, but there is a jumper on the board to disable it. We flipped it
and got a message during POST about it not being present. Additionally
all IPMI functions did nothing (hung, but interruptable) which is what
you'd expect. I think it really is disabled.

In this state, I re-ran the previous tests, with identical results. That
is:

- "modprobe i2c_i801" succeeds
- "modprobe i2c_i801 disable_features=0x10" succeeds
- With interrupts disabled, "modprobe ics932s401"
- With interrupts enabled, "modprobe ics932s401" hangs
- With interrupts enabled, "i2cget 4 0x50 0x00" hangs

I'll leave the BMC disabled for now in case that's important for further
testing. If you need other tests run with the BMC enabled, I'll use a
differen machine.

Cheers,
Rob.
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