2.6.24-rc3-git3: usb hardware interrupts using 25% of CPU time

I installed Linux 2.6.24-rc3-git3 on a PPC based Apple Powerbook G4 
system. Now with top I see that over 20% of CPU time is used by hardware 
interrupts. Looking at /proc/interrupts, the number in the row 
ohci_hcd:usb1 is rising very quickly:

$ cat /proc/interrupts 
           CPU0       
 21:          1   MPIC 1    Edge      i2sbus: i2s-a (tx)
 24:      11008   MPIC 1    Level     ide1
 25:      33608   MPIC 1    Level     VIA-PMU
 26:         56   MPIC 1    Level     keywest i2c
 27:          1   MPIC 1    Edge      i2sbus: i2s-a (rx)
 29:     281578   MPIC 1    Level     ohci_hcd:usb1
 30:          0   MPIC 1    Level     i2sbus: i2s-a (control)
 31:          0   MPIC 1    Level     i2sbus: i2s-b (control)
 33:          1   MPIC 1    Edge      i2sbus: i2s-b (tx)
 34:          1   MPIC 1    Edge      i2sbus: i2s-b (rx)
 39:      41611   MPIC 1    Level     ide0
 40:          2   MPIC 1    Level     ohci1394
 41:          0   MPIC 1    Level     eth0
 42:          0   MPIC 1    Level     keywest i2c
 47:       2826   MPIC 1    Level     GPIO1 ADB
 48:      58633   MPIC 1    Level     radeon@pci:0000:00:10.0
 52:      18961   MPIC 1    Level     b43
 53:          1   MPIC 1    Level     yenta
 61:          1   MPIC 1    Edge      headphone-detect
 63:          0   MPIC 1    Level     ohci_hcd:usb2, ohci_hcd:usb3, 
ehci_hcd:usb4
BAD:     187917

$ lspci -nn
0000:00:0b.0 Host bridge [0600]: Apple Computer Inc. UniNorth 2 AGP 
[106b:0034]
0000:00:10.0 VGA compatible controller [0300]: ATI Technologies Inc RV350 
[Mobility Radeon 9600 M10] [1002:4e50]
0001:10:0b.0 Host bridge [0600]: Apple Computer Inc. UniNorth 2 PCI 
[106b:0035]
0001:10:12.0 Network controller [0280]: Broadcom Corporation BCM4306 
802.11b/g Wireless LAN Controller [14e4:4320] (rev 03)
0001:10:13.0 CardBus bridge [0607]: Texas Instruments PCI1510 PC card 
Cardbus Controller [104c:ac56]
0001:10:17.0 Unknown class [ff00]: Apple Computer Inc. KeyLargo/Intrepid 
Mac I/O [106b:003e]
0001:10:19.0 USB Controller [0c03]: Apple Computer Inc. KeyLargo/Intrepid 
USB [106b:003f]
0001:10:1a.0 USB Controller [0c03]: Apple Computer Inc. KeyLargo/Intrepid 
USB [106b:003f]
0001:10:1b.0 USB Controller [0c03]: NEC Corporation USB [1033:0035] (rev 
43)
0001:10:1b.1 USB Controller [0c03]: NEC Corporation USB [1033:0035] (rev 
43)
0001:10:1b.2 USB Controller [0c03]: NEC Corporation USB 2.0 [1033:00e0] 
(rev 04)
0002:24:0b.0 Host bridge [0600]: Apple Computer Inc. UniNorth 2 Internal 
PCI [106b:0036]
0002:24:0d.0 Unknown class [ff00]: Apple Computer Inc. UniNorth/Intrepid 
ATA/100 [106b:003b]
0002:24:0e.0 FireWire (IEEE 1394) [0c00]: Apple Computer Inc. UniNorth 2 
FireWire [106b:0031] (rev 81)
0002:24:0f.0 Ethernet controller [0200]: Apple Computer Inc. UniNorth 2 
GMAC (Sun GEM) [106b:0032] (rev 80)


Full dmesg, .config and lsmod output can be found on 
http://artipc10.vub.ac.be/linux-2.6.24-rc3-git3/

-- 
Frederik Himpe