[PATCH] Re: Screen corruption in 2.4.18

Steven Walter (srwalter@yahoo.com)
Sun, 24 Mar 2002 09:59:30 -0600

This patch fixes a screen corruption bug seen on VIA KM133 mainboards.
As it stands, we disable bits 5, 6, and 7 of register offset 55 in order
to disable the memory write queue, which was causing us trouble before.
However, the clearing of bits 5 and 6 is causing us trouble now. Whenever
they're cleared, the screen gets static across it, roughly corresponding
to IDE/PCI activity. I spoke to one of the developers involved in the
original fix, and he suggested that we go ahead and not clear bits 5 and 6
on these boards, and that he was aware of several instances where clearing
them causes trouble.

Here is a patch which should apply cleanly to everyone's tree, which
only clears bit 7 on all chips except the KT266. No problems have been
reported there, so I'm leaving well enough alone. Please apply.


In a time of universal deceit, telling the truth is a revolutionary act.
			-- George Orwell
He's alive.  He's alive!  Oh, that fellow at RadioShack said I was mad!
Well, who's mad now?
			-- Montgomery C. Burns

--- linux/arch/i386/kernel/pci-pc.c~ Sun Mar 24 09:43:14 2002 +++ linux/arch/i386/kernel/pci-pc.c Sun Mar 24 09:43:23 2002 @@ -1197,16 +1197,19 @@ { u8 v; int where = 0x55; + int mask = 0x7f; /* Clearing bits 5 and 6 on the ProSavage KM133 + * causes strange screen corruption, so we don't */ 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 */ + mask = 0x1f; /* clear bits 5, 6, 7 */ } pci_read_config_byte(d, where, &v); if (v & 0xe0) { - printk("Disabling VIA memory write queue: [%02x] %02x->%02x\n", where, v, v & 0x1f); - v &= 0x1f; /* clear bits 5, 6, 7 */ + printk("Disabling VIA memory write queue: [%02x] %02x->%02x\n", where, v, v & mask); + v &= mask; pci_write_config_byte(d, where, v); } } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/