I am trying to use USB devices on a 4kc malta board. I see no problems from USB unless a device (any device, apparently) is plugged in to a USB port. After that, interrupts stop working (for everything, not just USB, as far as I can tell). I jave seen this on 2.6.8.1, 2.6.10, and 2.6.11-rc2. I have traced this down to the point where the mips_pcibios_iack routine sometimes gets an irq value of 0xFF. I put in a BUG_ON that condition, and it looks to me as though interrupts are happening during the interrupt service routine. I am attaching the backtrace below. Does this look familiar to anyone? thanks, --Guy backtrace from mips_pcibios_iack() when irq == 0xFF (2.6.10 kernel from mips.org CVS): Call Trace: [<801008a8>] mipsIRQ+0x128/0x180 [<8023b398>] hcd_submit_urb+0x0/0x898 [<80126ba0>] do_softirq+0x8c/0xb8 [<801069ac>] timer_interrupt+0x128/0x270 [<80126a20>] __do_softirq+0x50/0x144 [<80126ba0>] do_softirq+0x8c/0xb8 [<80106b34>] ll_timer_interrupt+0x40/0x4c [<80100890>] mipsIRQ+0x110/0x180 [<80100f64>] malta_hw0_irqdispatch+0x1e4/0x20c [<8023b398>] hcd_submit_urb+0x0/0x898 [<801008a8>] mipsIRQ+0x128/0x180 [<80102040>] handle_bp_int+0x18/0x38 [<802b70e8>] skb_read_and_csum_bits+0x0/0xb4 [<8012b3b0>] upate_process_times+0xe4/0x14c [<80100f64>] malta_hw0_irqdispatch+0x1e4/0x20c [<8023b398>] hcd_submit_urb+0x0/0x898 [<80106b34>] ll_timer_interrupt+0x40/0x4c [<801008a8>] mipsIRQ+0x128/0x180 [<80106b34>] ll_timer_interrupt+0x40/0x4c [<80100f80>] malta_hw0_irqdispatch+0x200/0x20c [<801008a8>] mipsIRQ+0x128/0x180 [<80100f64>] malta_hw0_irqdispatch+0x1e4/0x20c [<8023b398>] hcd_submit_urb+0x0/0x898 [<8014be14>] cache_fee_debugcheck+0x258/0x2d4 [<8014bde4>] cache_free_debugcheck+0x228/0x2d [<801008a8>] mipsIRQ+0x128/0x180 [<80102040>] handle_bp_int+0x18/0x38 [<8024ef48>] kfree_skbmem+0x14/0x30 [<80100f64>] malta_hw0_irqdispatch+0x1e4/0x20c [<8023b398>] hcd_submit_urb+0x0/0x898 [<8011cef4>] tr_to_wake_up+0x84/0x178 [<801008a8>] mipsIRQ+0x128/0x180 [<80100f80>] malta_hw0_irqdispatch+0x200/0x20c [<8011dcf8>] __wake_up_common+0x68/0xb8 [<8024e358>] alloc_skb+0x58/0xf4 [<801008a8>] mipsIRQ+0x128/0x180 [<80240000>] usb_rmove_sysfs_dev_files+0xac/0xe0 [<80100f64>] malta_hw0_rqdispatch+0x1e4/0x20c [<8023b398>] hcd_submit_urb+0x0/0x898 [<801008a8>] mipsIRQ+0x128/0x180 [<c0046300>] init_stall_timer+0x50/0x60 [uhci_hcd] [<80102040>] handle_bp_int+0x18/0x38 [<8011cef4>] try_to_wake_up+0x84/0x178 [<80100f64>] malta_hw0_irqdispatch+0x1e4/0x0c [<8023b398>] hcd_submit_urb+0x0/0x898 [<801008a8>] mipsIRQ+0x128/0x180 [<80100f80>] malta_hw0_irqdispatch+0x2000x20c [<80126ba0>] do_softirq+0x8c/0xb8 [<80106b34>] ll_timer_interrupt+0x40/0x4c [<801008a8>] mipsIRQ+0x128/0x180 [<80100890>] mipsIRQ+0x110/0x180 [<801011ec>] r4k_wait+0x0/0xc [<8023b398>] hcd_submit_urb+0x0/0x898 [<80102c44>] cpu_idle+0x3c/0x60 [<801011f0>] r4k_wait+0x4/0xc [<8010041c>] rest_init+0x1c/0x28 [<80122064>] printk+0x2c/0x38 [<8032d96c>] start_kernel+0x1bc/0x264 [<8032d95c>] start_kernel+0x1ac/0x264 [<8032d30c>] unknown_bootoption+0x0/0x304
