USBDMSC emulated device does not work on FreeBSD

Hi,

recently I got PolarFire SoC FPGA based board I am working on FreeBSD
support for. As a non volatile storage, it has eNVM used for HSS and
eMMC as disk device.

After reset, first thing run is HSS, which loads U-Boot from eMMC and
usual boot process continues. It is possible, however, break the
process and issue 'usbdmsc' command on HSS prompt. eMMC is then
presented as USB disk.

This works on Windows, and one or more (depends on partition table used
on eMMC) disk drives are presented to system. It is possible to use
balenaEtcher software to put some image there and do something with it.

This does not work on FreeBSD. I see device being attached after
starting 'usbdmsc' command, but no USB drive is being created. Could
someone help me to diagnose this? Which command output (maybe
'usbconfig <something>') could offer some hint?

Regards,
Milan