stack exception when doing hciattach

I am trying to enable Bluetooth interface for CSR8811 chipset on a phytec board(imx6ul arm). Kernel is 4.8 I am getting an exception when doing:

# hciattach /dev/ttyACM0 bcsp
# hciattach /dev/ttyACM0 bcsp
[  157.902406] INFO: rcu_sched self-detected stall on CPU
[  157.907628]  0-...: (2600 ticks this GP) idle=21b/140000000000002/0 softirq=8480/8480 fqs=0
[  157.916085]   (t=2600 jiffies g=4247 c=4246 q=48)
[  157.920841] rcu_sched kthread starved for 2600 jiffies! g4247 c4246 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
[  157.930253] rcu_sched       S c0905b98     0     7      2 0x00000000
[  157.936673] Backtrace:
[  157.939180] [<c090594c>] (__schedule) from [<c09060dc>] (schedule+0x48/0xa0)
[  157.946247]  r10:dffc84c0 r9:ffffffff r8:c0e02100 r7:00000000 r6:de48bea0 r5:dffc84c0
[  157.954204]  r4:de48a000
[  157.956787] [<c0906094>] (schedule) from [<c090a998>] (schedule_timeout+0x218/0x318)
[  157.964543]  r5:dffc84c0 r4:ffffbe56
[  157.968193] [<c090a780>] (schedule_timeout) from [<c018a31c>] (rcu_gp_kthread+0x4f0/0x840)
[  157.976472]  r10:c0e15680 r9:00000000 r8:00000001 r7:00000001 r6:c0e156d0 r5:c0e156f8
[  157.984429]  r4:c0e15440
[  157.987013] [<c0189e2c>] (rcu_gp_kthread) from [<c0145ddc>] (kthread+0xdc/0xf8)
[  157.994336]  r7:c0189e2c
[  157.996919] [<c0145d00>] (kthread) from [<c0107eb0>] (ret_from_fork+0x14/0x24)
[  158.004155]  r7:00000000 r6:00000000 r5:c0145d00 r4:de435040
[  158.009977] Task dump for CPU 0:
[  158.013230] hciattach       R running      0   856    847 0x00000003
[  158.019646] Backtrace:
[  158.022146] [<c010c46c>] (dump_backtrace) from [<c010c664>] (show_stack+0x18/0x1c)
[  158.029734]  r7:00000240 r6:c0e6db57 r5:0000034f r4:ddfd4800
[  158.035507] [<c010c64c>] (show_stack) from [<c015101c>] (sched_show_task+0x11c/0x22c)
[  158.043368] [<c0150f00>] (sched_show_task) from [<c0153d14>] (dump_cpu_task+0x34/0x44)
[  158.051298]  r6:c0e15440 r5:00000000 r4:00000000
[  158.056008] [<c0153ce0>] (dump_cpu_task) from [<c01cf058>] (rcu_dump_cpu_stacks+0xa4/0xc8)
[  158.064286]  r5:00000000 r4:c0e15440
[  158.067930] [<c01cefb4>] (rcu_dump_cpu_stacks) from [<c018b258>] (rcu_check_callbacks+0x6f4/0x8b4)
[  158.076902]  r9:c0e15d44 r8:c0e02b18 r7:1f256000 r6:c0d76180 r5:dffcc180 r4:c0e15440
[  158.084789] [<c018ab64>] (rcu_check_callbacks) from [<c018e5c8>] (update_process_times+0x38/0x64)
[  158.093675]  r10:c01a15c8 r9:dffc964c r8:dffc9640 r7:00000024 r6:c2fb3fd3 r5:00000000
[  158.101630]  r4:ddfd4800
[  158.104214] [<c018e590>] (update_process_times) from [<c01a15c4>] (tick_sched_handle+0x50/0x54)
[  158.112927]  r5:dd8ff940 r4:dffc9908
[  158.116570] [<c01a1574>] (tick_sched_handle) from [<c01a1628>] (tick_sched_timer+0x60/0xac)
[  158.124951] [<c01a15c8>] (tick_sched_timer) from [<c018f5b4>] (__hrtimer_run_queues+0xc8/0x1e4)
[  158.133662]  r7:00000000 r6:c0e22828 r5:dffc9908 r4:dffc95c0
[  158.139440] [<c018f4ec>] (__hrtimer_run_queues) from [<c018f8e4>] (hrtimer_interrupt+0xbc/0x210)
[  158.148241]  r10:dffc9678 r9:dffc9698 r8:dffc9600 r7:dffc96b8 r6:ffffffff r5:00000003
[  158.156196]  r4:dffc95c0
[  158.158781] [<c018f828>] (hrtimer_interrupt) from [<c06b7c5c>] (mxc_timer_interrupt+0x3c/0x44)
[  158.167408]  r10:c0e6db92 r9:de41d000 r8:00000010 r7:dd8ff874 r6:00000000 r5:de41d000
[  158.175365]  r4:de402440
[  158.177949] [<c06b7c20>] (mxc_timer_interrupt) from [<c017c4c0>] (__handle_irq_event_percpu+0x8c/0x124)
[  158.187356]  r5:de41d000 r4:de402500
[  158.191001] [<c017c434>] (__handle_irq_event_percpu) from [<c017c57c>] (handle_irq_event_percpu+0x24/0x60)
[  158.200668]  r10:00000000 r9:de406000 r8:00000001 r7:dd8ffad0 r6:c0e10120 r5:de41d000
[  158.208622]  r4:de41d000
[  158.211201] [<c017c558>] (handle_irq_event_percpu) from [<c017c5f8>] (handle_irq_event+0x40/0x64)
[  158.220086]  r5:de41d060 r4:de41d000
[  158.223728] [<c017c5b8>] (handle_irq_event) from [<c017fd74>] (handle_fasteoi_irq+0xd4/0x1ac)
[  158.232266]  r7:dd8ffad0 r6:c0e10120 r5:de41d060 r4:de41d000
[  158.238045] [<c017fca0>] (handle_fasteoi_irq) from [<c017b9cc>] (generic_handle_irq+0x28/0x3c)
[  158.246671]  r7:dd8ffad0 r6:c0e02b18 r5:00000010 r4:c0d73fa4
[  158.252449] [<c017b9a4>] (generic_handle_irq) from [<c017bd24>] (__handle_domain_irq+0x6c/0xe8)
[  158.261177] [<c017bcb8>] (__handle_domain_irq) from [<c01015f8>] (gic_handle_irq+0x58/0xb8)
[  158.269542]  r9:c0e02c7c r8:e0804000 r7:c0e22a40 r6:dd8ff940 r5:000003eb r4:e080400c
[  158.277422] [<c01015a0>] (gic_handle_irq) from [<c010d2b0>] (__irq_svc+0x70/0x98)
[  158.284921] Exception stack(0xdd8ff940 to 0xdd8ff988)
[  158.290001] f940: 00000001 00000110 00000000 ddfd4800 dda57f00 60070113 00000000 dde98164
[  158.298204] f960: dde98160 c0e02b18 c0e70b40 dd8ff9ac dd8ff938 dd8ff990 c016ec14 c05e1b00
[  158.306397] f980: 60070113 ffffffff
[  158.309899]  r10:c0e70b40 r9:dd8fe000 r8:dde98160 r7:dd8ff974 r6:ffffffff r5:60070113
[  158.317856]  r4:c05e1b00
[  158.320443] [<c05e1a20>] (__usb_hcd_giveback_urb) from [<c05e1bb0>] (usb_giveback_urb_bh+0x90/0xcc)
[  158.329502]  r7:dde98164 r6:dde98184 r5:00000000 r4:dd8ff9b0
[  158.335278] [<c05e1b20>] (usb_giveback_urb_bh) from [<c0129b4c>] (tasklet_action+0x9c/0x154)
[  158.343730]  r8:00000000 r7:dd8fe000 r6:00000000 r5:dde98190 r4:dde9818c
[  158.350568] [<c0129ab0>] (tasklet_action) from [<c0129d9c>] (__do_softirq+0x12c/0x298)
[  158.358499]  r10:40000006 r9:c0e02080 r8:00000100 r7:c0e02098 r6:dd8fe000 r5:00000006
[  158.366454]  r4:00000000
[  158.369032] [<c0129c70>] (__do_softirq) from [<c012a280>] (irq_exit+0xc8/0x13c)
[  158.376355]  r10:00000000 r9:de406000 r8:00000001 r7:00000000 r6:c0e02b18 r5:00000000
[  158.384310]  r4:c0d73fa4
[  158.386890] [<c012a1b8>] (irq_exit) from [<c017bd2c>] (__handle_domain_irq+0x74/0xe8)
[  158.394747] [<c017bcb8>] (__handle_domain_irq) from [<c01015f8>] (gic_handle_irq+0x58/0xb8)
[  158.403113]  r9:c0e02c7c r8:e0804000 r7:c0e22a40 r6:dd8ffad0 r5:000003eb r4:e080400c
[  158.410992] [<c01015a0>] (gic_handle_irq) from [<c010d2b0>] (__irq_svc+0x70/0x98)
[  158.418491] Exception stack(0xdd8ffad0 to 0xdd8ffb18)
[  158.423566] fac0:                                     00000001 00000110 00000000 ddfd4800
[  158.431768] fae0: a0070013 dde9827c dde7d800 a0070013 00000081 dde98000 dde9827c dd8ffb34
[  158.439967] fb00: dd8ffac8 dd8ffb20 c016ec14 c090b33c 20070013 ffffffff
[  158.446594]  r10:dde9827c r9:dd8fe000 r8:00000081 r7:dd8ffb04 r6:ffffffff r5:20070013
[  158.454550]  r4:c090b33c
[  158.457135] [<c090b300>] (_raw_spin_unlock_irqrestore) from [<c05fdf00>] (ehci_urb_enqueue+0xe8/0xdbc)
[  158.466457]  r5:00000000 r4:dd8ffb68
[  158.470104] [<c05fde18>] (ehci_urb_enqueue) from [<c05e3500>] (usb_hcd_submit_urb+0xb4/0x86c)
[  158.478643]  r10:ddfd9c00 r9:00000003 r8:024000c0 r7:00000000 r6:dde98000 r5:dde7d808
[  158.486599]  r4:dde7d800
[  158.489180] [<c05e344c>] (usb_hcd_submit_urb) from [<c05e4c54>] (usb_submit_urb+0x2a8/0x4fc)
[  158.497631]  r10:ddfd9c00 r9:00000003 r8:00000204 r7:00000002 r6:dd803c00 r5:024000c0
[  158.505587]  r4:dde7d800
[  158.508190] [<c05e49ac>] (usb_submit_urb) from [<bf00424c>] (acm_submit_read_urb+0x48/0x8c [cdc_acm])
[  158.517426]  r10:ddfd9c00 r9:00000102 r8:de788800 r7:de788b64 r6:de788800 r5:0000000f
[  158.525382]  r4:024000c0
[  158.527982] [<bf004204>] (acm_submit_read_urb [cdc_acm]) from [<bf005a34>] (acm_port_activate+0x13c/0x1a4 [cdc_acm])
[  158.538520]  r7:0000000f r6:de788d38 r5:00000000 r4:de78880c
[  158.544306] [<bf0058f8>] (acm_port_activate [cdc_acm]) from [<c048b944>] (tty_port_open+0x88/0xc8)
[  158.553281]  r9:00000102 r8:c1641b54 r7:de63e8c0 r6:de788930 r5:ddfd9c00 r4:de78880c
[  158.561171] [<c048b8bc>] (tty_port_open) from [<bf005484>] (acm_tty_open+0x20/0x24 [cdc_acm])
[  158.569710]  r9:00000102 r8:c1641b54 r7:dda4c068 r6:0a600000 r5:de63e8c0 r4:ddfd9c00
[  158.577608] [<bf005464>] (acm_tty_open [cdc_acm]) from [<c048418c>] (tty_open+0xbc/0x674)
[  158.585816] [<c04840d0>] (tty_open) from [<c02226d8>] (chrdev_open+0xa4/0x180)
[  158.593056]  r10:dd8ffea8 r9:dd8ffe20 r8:00000000 r7:c0a3bf70 r6:de63e8c0 r5:dda4c068
[  158.601011]  r4:ddeae140
[  158.603592] [<c0222634>] (chrdev_open) from [<c021b270>] (do_dentry_open+0x1ec/0x310)
[  158.611436]  r7:c0222634 r6:de63e8c8 r5:dda4c068 r4:de63e8c0
[  158.617212] [<c021b084>] (do_dentry_open) from [<c021c448>] (vfs_open+0x54/0x84)
[  158.624623]  r9:dd8ffe20 r8:00000000 r7:00000102 r6:00000000 r5:de63e8c0 r4:dd8ffea8
[  158.632511] [<c021c3f4>] (vfs_open) from [<c022c428>] (path_openat+0x384/0xfbc)
[  158.639836]  r6:00000000 r5:dd8fff5c r4:00000000
[  158.644546] [<c022c0a4>] (path_openat) from [<c022e3e8>] (do_filp_open+0x68/0xcc)
[  158.652042]  r10:00000000 r9:dd8fe000 r8:c0107fc4 r7:00000001 r6:dd8fff5c r5:dd8ffea8
[  158.659997]  r4:00000003
[  158.662579] [<c022e380>] (do_filp_open) from [<c021c7f0>] (do_sys_open+0x108/0x1c8)
[  158.670249]  r7:00000005 r6:dda86000 r5:ffffff9c r4:00000003
[  158.676026] [<c021c6e8>] (do_sys_open) from [<c021c8d0>] (SyS_open+0x20/0x24)
[  158.683176]  r9:dd8fe000 r8:c0107fc4 r7:00000005 r6:bea62d84 r5:bea61c08 r4:00037390
[  158.691063] [<c021c8b0>] (SyS_open) from [<c0107e20>] (ret_fast_syscall+0x0/0x1c)

I have tried looking at the functions before the exception as they are listed in the stack trace and make small changes see where could be the problem. But was not successfully. I have also compared the USB stack with the one in an earlier version: 4.6 but could not see what difference could lead to this crash.

does anybody have experience with this topic or could give some advice on hardware to proceed?

Thanks in advance