Coreboot on the x230

After living with my old coreboot installation for more than 18 month, i recently decided to build a new image and flash it. So i downloaded a coreboot 4.7 archive, extracted it and started building. I wanted a coreboot image with grub as a payload, but this time i didn’t want to build the grub payload myself, but let coreboot do the dirty work. To these are the changes i made to the default coreboot config:

Mainboard vendor (Lenovo)
Mainboard model (ThinkPad X230)
ROM chip size (4096 KB (4 MB))
Add a payload (GRUB2)  --->
GRUB2 version (2.02)  --->
(cryptodisk luks lvm gcry_rijndael gcry_sha256 usbserial_ftdi usbserial_pl2303) Extra modules to include in GRUB image
Include GRUB2 runtime config file into ROM image
(grub.cfg) Path of mygrub.cfg

and this is the corresponding mygrub.cfg file- it is based on the common.cfg grub config from the libreboot project:

function try_isolinux_config {
	set root="${1}"
	for dir in '' /boot; do
		if [ -f "${dir}"/isolinux/isolinux.cfg ]; then
			syslinux_configfile -i "${dir}"/isolinux/isolinux.cfg
		elif [ -f "${dir}"/syslinux/syslinux.cfg ]; then
			syslinux_configfile -s "${dir}"/syslinux/syslinux.cfg
		fi
	done
}
function search_isolinux {
	for i in 0 1; do
		# raw devices
		try_isolinux_config "(${1}${i})"
		for part in 1 2 3 4 5; do
			# MBR/GPT partitions
			try_isolinux_config "(${1}${i},${part})"
		done
	done
}

function decrypt {
        insmod luks
        insmod cryptodisk
        cryptomount (ahci0,msdos1)
        insmod lvm
}

menuentry 'Load Operating System (incl. fully encrypted disks)  [l]' --hotkey='l' {
        decrypt
        if [ -f (lvm/vg--x230-root)/boot/grub.cfg ] ; then
                root=(lvm/vg--x230-root)
                configfile /boot/grub.cfg
        fi
}

menuentry 'Debian GNU/Linux [d]' --hotkey='d' {
        decrypt
        root=(lvm/vg--x230-root)
        linux /vmlinuz
        initrd /initrd.img
}

menuentry 'Debian GNU/Linux Old [o]' --hotkey='o' {
        decrypt
        root=(lvm/vg--x230-root)
        linux /vmlinuz.old
        initrd /initrd.img.old
}

menuentry 'Search ISOLINUX menu (AHCI)  [a]' --hotkey='a' {
	search_isolinux ahci
}
menuentry 'Search ISOLINUX menu (USB)  [u]' --hotkey='u' {
	search_isolinux usb
}
menuentry 'Search ISOLINUX menu (CD/DVD)  [c]' --hotkey='c' {
	insmod ata
	for dev in ata0 ata1 ata2 ata3 ahci1; do
		try_isolinux_config "(${dev})"
	done
}
menuentry 'Poweroff  [p]' --hotkey='p' {
	halt
}
menuentry 'Reboot  [r]' --hotkey='r' {
	reboot
}
coreboot grub