From: Krzysztof Helt <krzysztof.h1@wp.pl>
This patch unhides the SMBus on Compaq Deskpro EN

SFF P667 with the Intel 815E chipset. Unhiding it reveals

a THMC51 hardware monitoring chip.
Jean Delvare has checked that this machine has no ACPI

magic touching the SMBus nor the hardware monitoring chip,

so this should be safe.
The patch was tested on Fedora Core 9 with 2.6.25.4 kernel.
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>

Tested-by: Rafał Haładuda <rh1985@wp.pl>

CC: Jean Delvare <khali@linux-fr.org>
---

If someone owns the Compaq Deskpro EN machine, please

test the patch as well.
diff -urp linux-2.6.25/drivers/pci/quirks.c linux-new/drivers/pci/quirks.c

--- linux-2.6.25/drivers/pci/quirks.c	2008-05-27 21:58:34.380144607 +0200

+++ linux-new/drivers/pci/quirks.c	2008-05-30 23:12:57.510219450 +0200

@@ -1054,6 +1054,14 @@ static void __init asus_hides_smbus_host

 				 * its on-board VGA controller */

 				asus_hides_smbus = 1;

 			}

+		else if (dev->device == PCI_DEVICE_ID_INTEL_82815_CGC)

+			switch (dev->subsystem_device) {

+			case 0x001A: /* Compaq Deskpro EN SSF P667 815E */

+				/* Motherboard doesn't have host bridge

+				 * subvendor/subdevice IDs, therefore checking

+				 * its on-board VGA controller */

+				asus_hides_smbus = 1;

+			}

 	}

 }

 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_82845_HB,	asus_hides_smbus_hostbridge);

@@ -1068,6 +1076,7 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_I

 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_82915GM_HB, asus_hides_smbus_hostbridge);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_82810_IG3,	asus_hides_smbus_hostbridge);

+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_82815_CGC,	asus_hides_smbus_hostbridge);
 static void asus_hides_smbus_lpc(struct pci_dev *dev)

 {
--

Thanks Krzysztof; applied to linux-next.  I had to fix up a conflict by hand

though, would be good if you could double check it.
Thanks,

Jesse

--

Hi Jesse, hi Krzysztof,
Let it be noted that ACPI is only one of the possible offenders. SMM is

another one. The user reported that his fan speed was changing speeds so

something has to be acting upon temperature changes. This could be the

fan itself, or this could be SMM code changing the registers of the

chip.
At this point of the investigation, I am still not 100% sure that the

patch is safe. I'd say it is only safe if the user's fan is actually

self-regulated based on the temperature.
One easy way to test would be to verify what happens when the

temperature exceeds 53 degrees C (the high temperature limit) and 78

degrees C (the critical temperature limit). Typical SMM code would

change the high and low limits when the high limit is crossed, this

should be clearly visible in the output of "sensors".
BTW, Krzysztof, what about adding (read-only) support for the critical

limits to your thmc50 driver? It would be helpful in a situation like

this.
Another thing to check is whether the value of register 0x19 (analog

output) changes automatically when the fan speeds up.
Until these tests are done, I consider this patch possibly unsafe and
--

Jean Delvare

--

Ok, thanks for the heads up Jean, I'll keep this one out of the queue I send

to Linus until we get confirmation about its safety.
Thanks,

Jesse

--

On Wed, 11 Jun 2008 09:16:38 -0700
I should be able to confirm in about a week. Two guys are currently using

the patch with thmc50 sensor driver. 
Regards,

Krzysztof
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