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From: Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua>
Reply-To: vda@port.imtp.ilyichevsk.odessa.ua
To: Steven Walter <srwalter@hapablap.dyn.dhs.org>
Subject: Re: VIA Northing workaround /causing/ problems
Date: Mon, 4 Feb 2002 14:47:31 -0200
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On 3 February 2002 02:40, Steven Walter wrote:
> I recently upgraded my kernel from 2.4.10-pre6 to 2.4.18-pre2.  After
> doing so, X acted extremely weird; whenever just about anything
> happened, lines would appear across the screen, almost like static.
>
> After playing around with a few config options that I'd changed, with no
> results, I noticed the message about the VIA northbridge bug in dmesg.
> I commented out the line listing this chipset in pci-pc.c, recompiled,
> and sure enough that fixed the problem!
>
> This board is based on the KT33 chipset.  If anyone would like more
> information, email me.

Can you play with it a bit more?
Go to that file, uncomment it back, fiddle with
pci_fixup_via_northbridge_bug(): try to clear only bit 7,
then only 7 and 6 and see which cause it...
Make it print reg#, old, new contents:
...
printk("Trying to stomp on VIA Northbridge bug: [%02x] %02x->%02x\n", where, v, v & 0x1f);
...
etc.
Original function for your reference:

static void __init pci_fixup_via_northbridge_bug(struct pci_dev *d)
{
        u8 v;
        int where = 0x55;
        if (d->device == PCI_DEVICE_ID_VIA_8367_0) {
                where = 0x95; /* the memory write queue timer register is
                                 different for the kt266x's: 0x95 not 0x55 */
        }
        pci_read_config_byte(d, where, &v);
        if (v & 0xe0) {
                printk("Trying to stomp on VIA Northbridge bug...\n");
                v &= 0x1f; /* clear bits 5, 6, 7 */
                pci_write_config_byte(d, where, v);
        }
}
--
vda
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