MTRR problem in 2.4.7+ on Athlon+VIA? XFree86 can't write-combine framebuffer.

Hi...

If any kind soul out there has the time to investigate this I'd be very grateful.

I have a problem with the XFree86 4.1.0 nv driver failing to set up a write-combining mtrr range for my video card. This happens with both 2.4.9-31 and 2.4.7-10 (redhat kernels). The system is an AMD Athlon with VIA chipset (see attachments for details). KT133 chipset
TNT2 video card 8mb RAM
Epox EP-8KTA2 motherboard (onboard VIA audio).

Basically, the "nv" driver reports
(WW) NV(0): Failed to set up write-combining range (0xd4000000,0x800000) to XFree86.0.log. XFree86 works, but things like MPEG playback seem a bit slow.

I assume this is because cat /proc/mtrr looks like this before X starts:

reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0xd0000000 (3328MB), size= 128MB: uncachable, count=1

From reading the mtrr doco I gather that because 0xd0000000 + 128mb is already set up as an uncachable range, "nv" can't set up 0xd4000000 + 8mb as write-combining.

This uncachable range seems to be set up fairly early in the system startup. I created a little /etc/rc5.d/S00MTRRDUMP script to cat /proc/mtrr before any of the other S* scripts run, and it reported the same mtrr ranges above.

I've searched all through the 2.4.7-10 source code and can't see anything that I'm using that explicitly asks for MTRR_TYPE_UNCACHABLE, so I'm a bit perplexed. I've had a good look around the web and newsgroups with all the keyword combinations I can think of, but no luck. mtrr.c is v1.40.

The only thing that looks suspicious to me is some lines in dmesg refering to 'unknown bridge', but that might be completely OK, I'm not sure (See below).

ver_linux reports...

Gnu C                  2.96
Gnu make               3.79.1
binutils               2.11.90.0.8
util-linux             2.11f
mount                  2.11g
modutils               2.4.13
e2fsprogs              tune2fs
pcmcia-cs              3.1.22
PPP                    2.4.1
isdn4k-utils           3.1pre1
Linux C Library        2.2.4
Dynamic linker (ldd)   2.2.4
Procps                 2.0.7
Net-tools              1.60
Console-tools          0.3.3
Sh-utils               2.0.11
Modules Loaded         sr_mod ppp_deflate bsd_comp ppp_async ppp_generic slhc via82cxxx_audio uart401 ac97_codec sound soundcore scanner sg ide-scsi scsi_mod ide-cd cdrom nls_iso8859-1 nls_cp437 vfat fat usb-uhci usbcore ext3 jbd

cat /proc/iomem
00000000-0009fbff : System RAM
0009fc00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000f0000-000fffff : System ROM
00100000-07ffffff : System RAM
00100000-002b4b99 : Kernel code
002b4b9a-002cbccf : Kernel data
d0000000-d3ffffff : VIA Technologies, Inc. VT8363/8365 [KT133/KM133] d4000000-d5ffffff : PCI Bus #01
d4000000-d5ffffff : nVidia Corporation Vanta [NV6]
d6000000-d7ffffff : PCI Bus #01
d6000000-d6ffffff : nVidia Corporation Vanta [NV6]
ffff0000-ffffffff : reserved

The interesting bits of dmesg are:
...
Checking 'hlt' instruction... OK.
POSIX conformance testing by UNIFIX
mtrr: v1.40 (20010327) Richard Gooch ([email protected])
mtrr: detected mtrr type: Intel
PCI: PCI BIOS revision 2.10 entry at 0xfb3a0, last bus=1
PCI: Using configuration type 1
PCI: Probing PCI hardware
Unknown bridge resource 0: assuming transparent
PCI: Using IRQ router VIA [1106/0686] at 00:07.0
Applying VIA southbridge workaround.
PCI: Disabling Via external APIC routing
isapnp: Scanning for PnP cards...
isapnp: No Plug & Play device found
...
parport_pc: Via 686A parallel port: io=0x378
usb.c: registered new driver usbscanner
scanner.c: USB Scanner support registered.
mtrr: type mismatch for d4000000,800000 old: uncachable new: write-combining <<<<----- I'm pretty sure this is XFree86 trying to write-combine Via 686a audio driver 1.9.1
PCI: Found IRQ 10 for device 00:07.5
ac97_codec: AC97 Audio codec, id: 0x4943:0x4511 (ICE1232)
via82cxxx: board #1 at 0xDC00, IRQ 10
...

A few other dumps are attached (apologies if this is overkill).

I'm not on the mailing list, so please reply directly if you have any suggestions.

Thanks in advance,
David Houlder.

00:00.0 Host bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133] (rev 03)
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort+ >SERR- <PERR-
Latency: 8
Region 0: Memory at d0000000 (32-bit, prefetchable) [size=64M]
Capabilities: <available only to root>

00:01.0 PCI bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133 AGP] (prog-if 00 [Normal decode])
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz+ UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort+ >SERR- <PERR-
Latency: 0
Bus: primary=00, secondary=01, subordinate=01, sec-latency=0
Memory behind bridge: d6000000-d7ffffff
Prefetchable memory behind bridge: d4000000-d5ffffff
BridgeCtl: Parity- SERR- NoISA+ VGA+ MAbort- >Reset- FastB2B-
Capabilities: <available only to root>

00:07.0 ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super South] (rev 40)
Subsystem: VIA Technologies, Inc. VT82C686/A PCI to ISA Bridge
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping+ SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Latency: 0
Capabilities: <available only to root>

00:07.1 IDE interface: VIA Technologies, Inc. Bus Master IDE (rev 06) (prog-if 8a [Master SecP PriP])
Subsystem: VIA Technologies, Inc. Bus Master IDE
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Latency: 32
Region 4: I/O ports at d000 [size=16]
Capabilities: <available only to root>

00:07.2 USB Controller: VIA Technologies, Inc. UHCI USB (rev 16) (prog-if 00 [UHCI])
Subsystem: Unknown device 0925:1234
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Latency: 32, cache line size 08
Interrupt: pin D routed to IRQ 5
Region 4: I/O ports at d400 [size=32]
Capabilities: <available only to root>

00:07.4 Bridge: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 40)
Subsystem: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI]
Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Capabilities: <available only to root>

00:07.5 Multimedia audio controller: VIA Technologies, Inc. AC97 Audio Controller (rev 50)
Subsystem: VIA Technologies, Inc.: Unknown device 4511
Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Interrupt: pin C routed to IRQ 10
Region 0: I/O ports at dc00 [size=256]
Region 1: I/O ports at e000 [size=4]
Region 2: I/O ports at e400 [size=4]
Capabilities: <available only to root>

01:00.0 VGA compatible controller: nVidia Corporation Vanta [NV6] (rev 15) (prog-if 00 [VGA])
Subsystem: AOPEN Inc.: Unknown device 0032
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Latency: 32 (1250ns min, 250ns max)
Interrupt: pin A routed to IRQ 11
Region 0: Memory at d6000000 (32-bit, non-prefetchable) [size=16M]
Region 1: Memory at d4000000 (32-bit, prefetchable) [size=32M]
Expansion ROM at <unassigned> [disabled] [size=64K]
Capabilities: <available only to root>

processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 4
model name : AMD Athlon(tm) Processor
stepping : 2
cpu MHz : 801.827
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr syscall mmxext 3dnowext 3dnow
bogomips : 1599.07

Module Size Used by Tainted: P

ppp_deflate            41760   0 (autoclean)
bsd_comp                4352   0 (autoclean)
ppp_async               6752   0 (autoclean)
ppp_generic            19432   0 (autoclean) [ppp_deflate bsd_comp ppp_async]
slhc                    5504   0 (autoclean) [ppp_generic]
via82cxxx_audio        18400   1 (autoclean)
uart401                 6592   0 (autoclean) [via82cxxx_audio]
ac97_codec              9536   0 (autoclean) [via82cxxx_audio]
sound                  59628   0 (autoclean) [via82cxxx_audio uart401]
soundcore               4452   4 (autoclean) [via82cxxx_audio sound]
scanner                 7776   0 (unused)
sg                     28932   0 (autoclean)
ide-scsi                8352   0
scsi_mod               98840   2 [sg ide-scsi]
ide-cd                 27072   0
cdrom                  28672   0 [ide-cd]
nls_iso8859-1           2816   1 (autoclean)
nls_cp437               4320   1 (autoclean)
vfat                   10396   1 (autoclean)
fat                    33112   0 (autoclean) [vfat]
usb-uhci               21732   0 (unused)
usbcore                51936   1 [scanner usb-uhci]
ext3                   62624   3
jbd                    41156   3 [ext3]

Thats more likely because the Nv driver doesn't support Xv or Xvmc extensions, which most other drivers have and give you nice accelerated overlay/colourspace/scaling for video playback.

You can tweak the ranges yourself, deleting the uncachable one and putting it back as two ranges

The BIOS sets them up for you