u-boot error on Pi2, ** fs_devread read error - block

A Pi2 running armv7 alpha1 has presented a new error message
not seen before, at least by me. Perhaps it'll be of interest:

Resetting system ... 

U-Boot 2023.07.02 (Aug 11 2023 - 07:47:06 +0000)

DRAM:  948 MiB
RPI 2 Model B (0xa21041)
Core:  75 devices, 12 uclasses, devicetree: board
MMC:   mmc@7e300000: 1
Loading Environment from FAT... ** Bad device specification mmc 0 **
In:    serial
Out:   vidconsole
Err:   vidconsole
Net:   No ethernet found.
starting USB...
Bus usb@7e980000: USB DWC2
scanning bus usb@7e980000 for devices... cannot reset port 1!?
1 USB Device(s) found
       scanning usb for storage devices... 0 Storage Device(s) found
Hit any key to stop autoboot:  0 
U-Boot> usb storage
No storage devices, perhaps not 'usb start'ed..?
U-Boot> usb reset
resetting USB...
Bus usb@7e980000: USB DWC2
scanning bus usb@7e980000 for devices... unable to get device descriptor (error=-22)
cannot reset port 1!?
cannot reset port 2!?
cannot reset port 3!?
 ** fs_devread read error - block
5 USB Device(s) found
       scanning usb for storage devices... 1 Storage Device(s) found
U-Boot> <INTERRUPT> [I'd typed control-c thinking it was looping]
U-Boot> 

The machine had just finished a build/install cycle and was attempting
to reboot, which had been done successfully prior to that.

After a few minute's pause for reflection, I tried:
U-Boot> boot
MMC Device 0 not found
no mmc device at slot 0
switch to partitions #0, OK
mmc1 is current device
Scanning mmc 1:1...
No EFI system partition
No EFI system partition
Failed to persist EFI variables
BootOrder not defined
EFI boot manager: Cannot load any image
MMC Device 2 not found
no mmc device at slot 2

Device 0: Vendor: External Rev: 0204 Prod: USB3.0          
            Type: Hard Disk
            Capacity: 476940.0 MB = 465.7 GB (976773168 x 512)
... is now current device

Since the only u-boot executable is on the USB hard disk
it looks like disk discovery is initially successful, but
something goes wrong afterward. It looked as if the usb
disk was found, but either that message was wrong or the
discovery forgotten. 

Next, the Pi2 alone was powercycled, which remained hung with
green LED on. A second powercycle booted successfully, no
complaints at all. The system presently reports:
bob@generic:~ % uname -a
FreeBSD generic 14.0-ALPHA2 FreeBSD 14.0-ALPHA2 armv7 1400096 #2 main-n264996-d5b5497e10fd: Wed Aug 23 16:29:57 UTC 2023     root@generic:/usr/obj/usr/src/arm.armv7/sys/GENERIC arm

Thanks for reading,

bob prohaska