Let's break down what's going on here and walk through the steps to resolve the system crash when inserting an FTDI USB cable after loading the cross-compiled ftdi_sio module.

Target Device Environment #

First, let's recap your device specs for clarity:

uname -a Output #

Linux localhost 2.6.30 #1 SMP PREEMPT Mon Jun 8 16:14:23 CEST 2015 mips GNU/Linux

cat /proc/cpuinfo Output #

system type : 963168_IADR
voice type : SI32261
processor : 0
cpu model : Broadcom4350 V8.0
BogoMIPS : 398.33
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : no
hardware watchpoint : no
ASEs implemented :
shadow register sets : 1
core : 0
VCED exceptions : not available
VCEI exceptions : not available
unaligned exceptions : 3
processor : 1
cpu model : Broadcom4350 V8.0
BogoMIPS : 402.43
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : no
hardware watchpoint : no
ASEs implemented :
shadow register sets : 1
core : 0
VCED exceptions : not available
VCEI exceptions : not available

Current Setup & Issue #

You attempted to cross-compile the ftdi_sio module for Linux 2.6.30, but found no MIPS architecture in arch/mips that supported SMP, MIPS32_R1, and big-endian mode simultaneously. So you modified arch/mips/Kconfig to add select SYS_SUPPORTS_SMP to the MIPS_MALTA architecture. Using the OpenWrt OpenWrt-Toolchain-brcm63xx-for-mips-gcc-4.3.3+cs_uClibc-0.9.30.1 toolchain, you successfully compiled and loaded the module—but inserting an FTDI USB cable caused a system crash, with this dmesg output:

[ 561.429000] Process khubd (pid: 69, threadinfo=8793c000, task=8790add0, tls=00000000)
[ 561.429000] Stack : 00000001 c448fdd4 c4494780 866a0980 87b7c000 00000001 c448fdd4 c44901c0
[ 561.429000] 00000000 80348ac8 000003e0 80117a68 802e97f0 866e6b80 8793fbb8 87820e00
[ 561.429000] 8111b93c 800db590 853a0bf8 80340000 85a947a8 800a5a84 802a52e8 80076f0c
[ 561.429000] 866e57d8 866ba63c 87820e00 800db590 853a0bf8 853a0bf8 00000001 800a5b4c
[ 561.429000] 0000a1ff 800dbe84 866e57ac 85a947a0 8793fc50 866ba63c 8793fc50 800dbc68
[ 561.429000] 00000000 866ba63c 866e57d8 853a0bf8 00000001 85a947a8 802e97f0 00000000
[ 561.429000] 87b7c068 800dd010 87b7c000 85a94780 85a94780 c0cd47e8 c0cd474c 85a947a0
[ 561.429000] 87b7c000 85a947a8 802e97f0 00000000 87b7c068 80181168 85a94780 80154664
[ 561.429000] 00000000 00000000 ffffffed 85a947a0 c0cd4780 85a947a0 87b7c000 801547d8
[ 561.429000] 802e1a70 8793fce8 866e6700 00000000 00000000 8793fcc8 80154944 80153be8
[ 561.429000] 870583c0 866b0000 802e2650 85a947a8 878dd650 86fd44b8 878de000 802e9820
[ 561.429000] 85a947a0 85a947d4 802ab200 80154a48 802e1a70 802ac7ec 00000000 00000000
[ 561.429000] 802e9820 85a947a0 00000000 801539ac 00000000 802ab200 87b7c000 85a947a8
[ 561.429000] 802e97f0 85a94780 85a947a0 801523f4 00000001 00000000 00000002 00000000
[ 561.429000] 00000001 00000028 85a947a0 85a94780 85a94780 00000000 866e6a08 802ab200
[ 561.429000] 87b7c000 866e6a00 00000001 00000001 85836e04 801803d8 00000002 87b7c070
[ 561.429000] 00000002 87b7c004 00000001 00000000 00000000 00000000 00001388 87b7c070
[ 561.429000] 85836e00 87a82c04 87b7c068 00000001 87a82c00 87b7c004 00000001 87b7c000
[ 561.429000] 802e9e54 87b7c068 00000002 87b7c070 802e9674 00000000 87a66868 80187370
[ 561.429000] 00000002 80154664 fffffffe 866e6700 8793fe10 87828438 ffffffed 87b7c068
[ 561.429000] 802e9e54 801547d8 802e1a70 8793fe50 866e6700 00000000 00000000 8793fe30
[ 561.429000] 80154944 80153be8 866bb2e0 866b0000 802e2650 87b7c070 878dd650 87828438
[ 561.429000] 878de000 802e9820 87b7c068 87b7c09c 87a5fd80 80154a48 802e1a70 802ac7ec
[ 561.429000] 00000000 00000000 802e9820 87b7c068 00000000 801539ac 00000000 87a5fd80
[ 561.429000] 00000002 87b7c070 802e9674 8793fea0 87b7c068 801523f4 87a66800 00000000
[ 561.429000] 000000bd 00000081 3138393a 31323900 00000000 87b7c000 87b7c068 00000000
[ 561.429000] 87b7c000 87a5fd80 00000002 00000000 87a66800 00000001 87a66800 80179aec
[ 561.429000] 0000000a 87b7c000 85348380 87a5fd80 00000000 87b7c000 85348380 8017b05c
[ 561.429000] 87a5fd80 8002b9b4 00000001 8793ff28 0000000a 00000001 00000000 00000000
[ 561.429000] 000003e8 803280d0 80327884 01010001 00000101 00000000 8790add0 8004fa04
[ 561.429000] 8793ff38 8793ff38 87a66800 87a5fd80 00000000 87a66c00 87a5fe1c 87a5fea0
[ 561.429000] 00000002 87a5fd88 87a6689c 87a5fdc8 87a5fdc4 87a5fdc0 87a5fea0 00000000
[ 561.429000] 00000001 87a669e0 00000000 8017a5d0 00000000 00000000 00000000 00000000
[ 561.429000] 00000000 00000000 00000000 8004f610 00000000 00000000 00000000 00000000
[ 561.429000] 8793c000 00000000 00000000 80014d34 10008d03 00000000 00000000 00000000
[ 561.429000] 00000000 00000000 45551450 75455555 054d0555 1d555544 54115154 555dd155
[ 561.429000] 15195545 05547516

Root Cause Breakdown #

The core issue here is that you're using the MIPS_MALTA reference architecture (modified to add SMP support) for a Broadcom brcm63xx-based device. Malta is a generic MIPS development platform, and its default configuration doesn't account for the specific hardware quirks, memory layout, or USB controller implementation of the Broadcom 963168_IADR and 4350 CPU. The panic in khubd (the USB hub daemon process) points to a mismatch between the generic USB stack code and the actual Broadcom USB host controller hardware, especially under SMP.

Step-by-Step Fixes #

1. Use the Correct Kernel Source for brcm63xx #

Stop using the generic Linux 2.6.30 kernel. Instead, use the OpenWrt brcm63xx 2.6.30 branch source or your modem's official kernel code. These sources include:

• Pre-configured support for Broadcom 963168_IADR and 4350 SMP
• Patches for the Broadcom USB host controller
• Correct memory and interrupt mappings for your device

2. Configure the Kernel for brcm63xx (Not Malta) #

When setting up your kernel build, target the brcm63xx platform directly instead of modifying Malta:

export ARCH=mips
export CROSS_COMPILE=mips-openwrt-linux-uclibc-
make menuconfig

In the menuconfig:

• Select System Type > Broadcom BCM63XX
• Enable SMP support under System Type
• Enable USB support > USB Host Controller > Broadcom BCM63XX EHCI support (or the correct controller for your device)
• Enable USB support > USB Serial Converter support > USB FTDI Single Port Serial Driver (CONFIG_USB_SERIAL_FTDI_SIO)

3. Verify Tool #