Howto unprotect mtd0 (no replies)

My dockstar still continue their jobs.

Therefore, I would like to update uboot.
But it sems my nand (mtd0) is protected no matter how the Dockstar boots (usb, net).

I can not remember what I did for that and now I can not install any new uboot.

Here is the issue (flag MTD_CAP_ROM instead of MTD_CAP_NANDFLASH):

mtd_debug info /dev/mtd0
mtd.type = MTD_NANDFLASH
mtd.flags = MTD_CAP_ROM
mtd.size = 1048576 (1M)
mtd.erasesize = 131072 (128K)
mtd.writesize = 2048 (2K)
mtd.oobsize = 64
regions = 0

# flash_unlock /dev/mtd0
flash_unlock: error!: could not open: /dev/mtd0
error 13 (Permission denied)

#flash_erase /dev/mtd0 0 4
flash_erase: error!: /dev/mtd0
error 13 (Permission denied)

Any solution welcome.