VIA 82C686B SouthBridge fixup in linux/drivers/pci/quirks.c

VIA 82C686B SouthBridge fixup in linux/drivers/pci/quirks.c

[Jeff S Wheeler]

Hi, I am not subscribed to the list.  Please CC me on replies.

The VIA686B SouthBridge bug workaround is not activated on motherboards
which have a VIA 82C686B that needs fixing, but not a VIA NorthBridge.  For
example, my Asus A7M266 has an AMD 761 NorthBridge, and the table at the end
of linux/drivers/pci/quirks.c thus does not attempt to apply the fix.
Someone suggested a fix against 2.4.4 in this thread, however it has not all
been fixed on 2.4.5 nor 2.4.5-ac22 (current, I believe).

Below is a patch to the __initdata table which causes the fix to be applied
based on detection of the buggy SouthBridge, and *not* the NorthBridge which
is commonly used with it.  This is the correct behavior, and was suggested
by someone during the thread I reference, however this aspect of the fix was
overlooked.

http://mailman.real-time.com/pipermail/linux-kernel/Week-of-Mon-20010430/032
013.html

---
Jeff S Wheeler           jsw@five-elements.com
Software Development        Five Elements, Inc


--- linux-2.4.5/drivers/pci/quirks.c.orig       Fri Jun 29 20:24:09 2001
+++ linux-2.4.5/drivers/pci/quirks.c    Fri Jun 29 20:58:14 2001
@@ -358,7 +358,7 @@
        { PCI_FIXUP_FINAL,      PCI_VENDOR_ID_INTEL,
PCI_DEVICE_ID_INTEL_82443BX_2,  quirk_natoma },
        { PCI_FIXUP_FINAL,      PCI_VENDOR_ID_SI,
PCI_DEVICE_ID_SI_5597,          quirk_nopcipci },
        { PCI_FIXUP_FINAL,      PCI_VENDOR_ID_SI,
PCI_DEVICE_ID_SI_496,           quirk_nopcipci },
-       { PCI_FIXUP_FINAL,      PCI_VENDOR_ID_VIA,
PCI_DEVICE_ID_VIA_8363_0,       quirk_vialatency },
+       { PCI_FIXUP_FINAL,      PCI_VENDOR_ID_VIA,
PCI_DEVICE_ID_VIA_82C686,       quirk_vialatency },
        { PCI_FIXUP_FINAL,      PCI_VENDOR_ID_VIA,
PCI_DEVICE_ID_VIA_82C597_0,     quirk_viaetbf },
        { PCI_FIXUP_HEADER,     PCI_VENDOR_ID_VIA,
PCI_DEVICE_ID_VIA_82C597_0,     quirk_vt82c598_id },
        { PCI_FIXUP_HEADER,     PCI_VENDOR_ID_VIA,
PCI_DEVICE_ID_VIA_82C586_3,     quirk_vt82c586_acpi },

Re: VIA 82C686B SouthBridge fixup in linux/drivers/pci/quirks.c

[Charl P. Botha]

On Fri, Jun 29, 2001 at 09:44:51PM -0400, Jeff S Wheeler wrote:
> The VIA686B SouthBridge bug workaround is not activated on motherboards
> which have a VIA 82C686B that needs fixing, but not a VIA NorthBridge.  For

> Below is a patch to the __initdata table which causes the fix to be applied
> based on detection of the buggy SouthBridge, and *not* the NorthBridge which
> is commonly used with it.  This is the correct behavior, and was suggested
> by someone during the thread I reference, however this aspect of the fix was

No, this is NOT correct behaviour.  Please read the pages at:
http://home.tiscalinet.de/au-ja/review-kt133a-1-en.html (and especially
click on "Bugfix for everybody"); this URL is in the code.  You will note
that it is explicitly stated that this fix is NOT meant for any other
Northbridge than VIA.  So, in short, if there is no BIOS update available
for your board, you're going to have to some more research.  The PCI
registers that are configured could have a totally different (and even
dangerous) effect on your configuration.

-- 
charl p. botha      | computer graphics and cad/cam 
http://cpbotha.net/ | http://www.cg.its.tudelft.nl/