FreeBSD CURRENT on CUBOX-i 4x4-300-D using 4GB RAM

[Ulrich Grey]

I have built a new u-boot using sysutils/u-boot-cubox-hummingboard,
but substituting the u-boot source tree from ports with a freshly 
cloned one:

git clone https://github.com/SolidRun/u-boot-imx6.git

Applying the patches from the port delivered a rejected chunk
whom I have applied "manually".

After building I have copied the  u-boot.imx file to the image file
as described in the README file.

Booting the system, ca. 4GB (instead of 2GB) of RAM was recognized:

FreeBSD 11.0-ALPHA3 #2 r301815M: Sat Jun 11 05:11:51 UTC 2016
    root at wqtest.intranet:/usr/obj/usr/src/sys/IMX6 arm
FreeBSD clang version 3.8.0 (tags/RELEASE_380/final 262564) (based on LLVM 3.8.0)
VT: init without driver.
CPU: Cortex A9-r2 rev 10 (Cortex-A core)
 Supported features: ARM_ISA THUMB2 JAZELLE THUMBEE ARMv4 Security_Ext
 WB enabled LABT branch prediction disabled
LoUU:2 LoC:2 LoUIS:2 
Cache level 1: 
 32KB/32B 4-way data cache WB Read-Alloc Write-Alloc
 32KB/32B 4-way instruction cache Read-Alloc
real memory  = 4025483264 (3839 MB)
avail memory = 3933708288 (3751 MB)
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs

But I was not able to use the external USB harddisks.
I got error messages like:
usb_err_nomem
kstack allocation failed.

After I added 
kern.nbuf="8000"
to /boot/loader.conf, the error messages disappeared.
The value "8000" is a guess, the old value was around 7100.
As a test I have successfully build a new kernel.
Only USB1 port is working.