Hi all,

[Please CC me in replies, I am currently not subscribed to LKML.]

Since about a month, I have severe issues with a cable modem connected 
via USB, which behaves like an ethernet-on-USB adapter with the CDCEther 
module. It worked for a couple of months without issues with 2.4.23 and 
2.4.26, but makes problems since the update to 2.4.27. Downgrading to 
the previous kernels did not help, so I suspect a changed IRQ routing 
caused by a reboot or due to the 2.4.27 update.

The problem manifests itself by the following syslog messages:

Aug 13 10:32:00 whisper kernel: usb_control/bulk_msg: timeout
Aug 13 10:32:35 whisper kernel: usb_control/bulk_msg: timeout
Aug 13 10:35:30 whisper kernel: usb_control/bulk_msg: timeout
Aug 13 10:51:08 whisper kernel: usb_control/bulk_msg: timeout
Aug 13 10:55:58 whisper kernel: usb_control/bulk_msg: timeout

whenever some transfer happens over the modem. During the first few 
hours after reboot, the messages seem harmless, but when running for a 
longer time the network interface (eth2 in this case) usually becomes 
unavailable and only a complete re-initialization of the USB subsystem 
by removing and modprobing all modules solves the issue.

After 2 weeks I have tracked the problem down to the usage of the 
agpgart module. When I boot the system without this module being loaded 
(and consequently without X running), the messages do not appear and the 
modem connection is stable. As soon as agpgart is loaded with

modprobe agpgart agp_try_unsupported=1

and X is started, the syslog messages start coming (also when no X 
application actually changes the display output, it just sits there).

Interestingly, when I stop X, the messages do not appear any more, 
although agpgart is still loaded. Currently, it seems like an interrupt 
conflict between the AGP and USB controllers.

[root@whisper ~]# cat /proc/interrupts
            CPU0
   0:     962727          XT-PIC  timer
   1:         10          XT-PIC  keyboard
   2:          0          XT-PIC  cascade
   8:          3          XT-PIC  rtc
   9:          0          XT-PIC  acpi
  10:          0          XT-PIC  usb-uhci, eth1
  11:     722702          XT-PIC  usb-uhci, eth0
  12:          0          XT-PIC  usb-uhci, via82cxxx
  14:      18553          XT-PIC  ide0
  15:      12351          XT-PIC  ide1
NMI:          0
LOC:          0
ERR:          0
MIS:          0

Doesn't show the IRQ of the AGP controller, so I am not sure. During 
initialization, the agpart module also doesn't tell:

Linux agpgart interface v0.99 (c) Jeff Hartmann
agpgart: Maximum main memory to use for agp memory: 409M
agpgart: Detected Via CLE266 chipset
agpgart: AGP aperture is 128M @ 0xd0000000
mtrr: 0xd8000000,0x2000000 overlaps existing 0xd8000000,0x800000
[drm] Initialized via 1.3.0 20040411 on minor 0: PCI device 1106:3122
mtrr: 0xd8000000,0x2000000 overlaps existing 0xd8000000,0x800000

The board is a VIA EPIA M-6000 with the following PCI config:

[root@whisper ~]# lspci
00:00.0 Host bridge: VIA Technologies, Inc.: Unknown device 3123
00:01.0 PCI bridge: VIA Technologies, Inc. VT8633 [Apollo Pro266 AGP]
00:0d.0 FireWire (IEEE 1394): VIA Technologies, Inc. OHCI Compliant IEEE 
1394 Host Controller (rev 80)
00:10.0 USB Controller: VIA Technologies, Inc. UHCI USB (rev 80)
00:10.1 USB Controller: VIA Technologies, Inc. UHCI USB (rev 80)
00:10.2 USB Controller: VIA Technologies, Inc. UHCI USB (rev 80)
00:10.3 USB Controller: VIA Technologies, Inc.: Unknown device 3104 (rev 82)
00:11.0 ISA bridge: VIA Technologies, Inc.: Unknown device 3177
00:11.1 IDE interface: VIA Technologies, Inc. Bus Master IDE (rev 06)
00:11.5 Multimedia audio controller: VIA Technologies, Inc. AC97 Audio 
Controller (rev 50)
00:12.0 Ethernet controller: VIA Technologies, Inc. Ethernet Controller 
(rev 74)
00:14.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139 
(rev 10)
01:00.0 VGA compatible controller: VIA Technologies, Inc.: Unknown 
device 3122 (rev 03)

ACPI is used, but I have tried each of the kernel options
acpi=off
pci=noacpi
pci=biosirq
with no change. The kernel is a vanilla 2.4.27 with the -epia1 patch 
and, for testing, also the most recent ACPI4linux patch (which seems 
rather minor) for 2.4.27-pre<something>.

Attached are the dmesg log after bootup, lsmod output (with modules 
loaded where it always works) and the kernel config.

Any ideas on what's up ? ACPI ? I have not yet tried to set the IRQ 
routing manually in the BIOS, because the options there are rather 
restricted and I'm not sure that it would help.

with best regards,
Rene