2.4.18 VIA MWQ patch (Athlon stomper) corrupts video with KT133/KM133

[Andre Pang]

Hi,

The VIA MWQ patch[1] that went into 2.4.18 seems to play havoc
with my video card, a ProSavage KM133.  I get a bunch of vertical
lines in text mode, and that's it; the text display is completely
corrupted.  If I use a VESA framebuffer, I get an effect similar
to the old CGA 'snow' whenever I see the hard disk being
accessed: random streaks appear across the screen.

If I clear only bit 7 of register 55 on my chipset to fix the
Athlon stomper bug (which is what the kernels before 2.4.18 did),
I seem to have no problems at all.  2.4.18 clears bits 5, 6 and 7
of register 55.  Does anybody have any idea what bits 5 and 6 do?
Does anybody know what the Windows VIA patches do for particular
motherboard (Asus A7VC)?

Perhaps we should revert this patch if systems are stable without
clearing bits 5/6.

    2:50(0) chiba:~% lspci
    00:00.0 Host bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133] (rev 81)
    00:01.0 PCI bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133 AGP]
    00:07.0 ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super South] (rev 40)
    00:07.1 IDE interface: VIA Technologies, Inc. Bus Master IDE (rev 06)
    00:07.2 USB Controller: VIA Technologies, Inc. UHCI USB (rev 1a)
    00:07.3 USB Controller: VIA Technologies, Inc. UHCI USB (rev 1a)
    00:07.4 Bridge: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 40)
    00:07.5 Multimedia audio controller: VIA Technologies, Inc. AC97 Audio Controller (rev 50)
    00:0d.0 Multimedia video controller: Brooktree Corporation Bt848 TV with DMA push (rev 12)
    00:0e.0 Ethernet controller: Intel Corp. 82557 [Ethernet Pro 100] (rev 0c)
    00:12.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139 (rev 10)
    01:00.0 VGA compatible controller: S3 Inc. ProSavage KM133 (rev 03)

    2:50(0) chiba:~% lspci -n
    00:00.0 Class 0600: 1106:0305 (rev 81)
    00:01.0 Class 0604: 1106:8305
    00:07.0 Class 0601: 1106:0686 (rev 40)
    00:07.1 Class 0101: 1106:0571 (rev 06)
    00:07.2 Class 0c03: 1106:3038 (rev 1a)
    00:07.3 Class 0c03: 1106:3038 (rev 1a)
    00:07.4 Class 0680: 1106:3057 (rev 40)
    00:07.5 Class 0401: 1106:3058 (rev 50)
    00:0d.0 Class 0400: 109e:0350 (rev 12)
    00:0e.0 Class 0200: 8086:1229 (rev 0c)
    00:12.0 Class 0200: 10ec:8139 (rev 10)
    01:00.0 Class 0300: 5333:8a26 (rev 03)

1. http://marc.theaimsgroup.com/?l=linux-kernel&m=100772126208656&w=2

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