>> The decision on whether HAB is enabled is solely based on the SEC_CONFIG >> fuse. The HAB FIELD_RETURN feature is able to permanently disable HAB on >> a CPU, after which it is able to boot unsigned firmware. U-Boot however >> does not take into account the FIELD_RETURN mode, and refuses to boot >> unsigned software when the feature is enabled. >> >> Also take the FIELD_RETURN fuse into account when deciding whether HAB >> is enabled. When The FIELD_RETURN fuse is blown, HAB is not enabled. >> >> Tested on i.MX8M Mini, i.MX8M Plus, i.MX8M Nano and i.MX6ULL > >The purpose of the field return fuse is to unlock a system when it is >returned to factory, right ?
That is the intention of the field return mode indeed. > >Can the system be re-locked afterward too ? No, the field return is enabled by a fuse, which cannot be reverted. The mode is intended to be able to perform investigations on broken devices, but these devices are not intended to go back into the field.
