linux-kernel - Re: [PATCH] pci-quirks: HP hides SMBus controller in Compaq nx9500 laptops

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Message-ID: <20090105200221.GA26115@rere.qmqm.pl>
Date:	Mon, 5 Jan 2009 21:02:21 +0100
From:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Pavel Machek <pavel@...e.cz>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci-quirks: HP hides SMBus controller in Compaq nx9500 laptops

On Mon, Jan 05, 2009 at 11:19:20AM -0800, Jesse Barnes wrote:
> On Wednesday, December 31, 1969 10:46 pm Pavel Machek wrote:
> > On Tue 2008-12-23 22:54:07, Micha? Miros?aw wrote:
> > > I found no references to SMBus in ACPI DSDT disassembly on my laptop
> > > so this should be safe.
> > >
> > > Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> > Well, it could still be used by smm bios traps...
> Also, the changelog doesn't include a description of what this patch fixes, if 
> anything.  Care to resend with an explanation Michal?

This patch enables SMBus controller on HP Compaq nx9500 laptop and
allowes to read SPD EEPROMs of the memory modules.
I found no references to SMBus in ACPI DSDT disassembly on my laptop, but
there are some additional devices on the bus (besides SPD chips).

rechot ~ # lspci -s 00:1f.3
00:1f.3 SMBus: Intel Corporation 82801EB/ER (ICH5/ICH5R) SMBus Controller (rev 02)

rechot ~ # i2cdetect -a 0
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-0.
I will probe address range 0x00-0x7f.
Continue? [Y/n] y
          0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
     00: -- -- -- -- -- -- -- -- 08 -- -- -- -- -- -- --
     10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
     20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
     30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
     40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --
     50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
     60: -- -- -- -- -- -- -- -- -- 69 -- -- -- -- -- --
     70: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

I observed no ill effects after scanning the bus, but YMMV.

Using the bus is probably not a good idea if the SMM code is really using
it, and so it might be better if this patch lies in the archives for now.
After I get the BIOS flashing to work I'll look into this.

Best Regards,
Michal Miroslaw
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