u-boot fw_env for SD card based boot

[Simon H <btsimonh@googlemail.com>]

Hi all,

Got Debian working nicely on an allwinner device with SD boot.

The uboot variables seem to be stored in a file boot.scr in mmcblk0p1
(or are they in /boot/boot.scr?)

Although the fw_env I have does seem to support the new style entry in
fw_env.config :

# VFAT example
/mnt/dos/boot.scr               0x0000          0x4000

If i copy the settings file file to somewhere (safe) and setup to use
the copied file, fw_env tries to read the 0x4000 bytes and fails (file
is only 1500 bytes long).  If I extend the file with zeros to 16k,
then fw_printenv works, but reports bad CRC (so fw_setenv basically
uses a default config, nothing like what I need...).
A subsequent fw_setenv DOES work.....(i.e. it has written a valid CRC).
So it seems like if the original boot.scr was >16k and had a valid
CRC, then the tools would work...

Is this a known issue with Debian uboot installs on SD card?
Is there an official way (that I have missed) of modifying the uboot
environment in this situation?

S