In board/freescale/common/imx/imx8-bootloader-prepare.sh, when
invoking mkimage_fit_atf.sh, the U-Boot DTB is passed as parameter, to
be included in the FIT image. This parameter usually comes from
BR2_ROOTFS_POST_SCRIPT_ARGS config option. The variable
BL33=u-boot.bin set in the invocation uses the u-boot image which is
including its embedded DTB. This means the U-Boot DTB is included
twice.
The upstream script mkimage_fit_atf.sh plus its Buildroot patch are
meant to use by default the nodtb variant and use the DTB in a
separate image. See [1] and [2].
The U-Boot default DTB which will be included in u-boot.bin image is
selected with U-Boot CONFIG_DEFAULT_DEVICE_TREE, or DEVICE_TREE
variable when invoking "make". If one of those option is not aligned
to the BR2_ROOTFS_POST_SCRIPT_ARGS config option, it's possible the
two included U-Boot DTBs are different. If such case happens, the
built-in DTB is always used, regardless of the other one, selected
with BR2_ROOTFS_POST_SCRIPT_ARGS.
For example, this case happens for TechNexion Pico Pi i.MX8M and
i.MX8MMini. Since the U-Boot defconfig assumes the nodtb version will
be used, it does not set the default DTB. The u-boot.bin will include
the fsl-imx8mm-evk instead. Including the wrong board DTB breaks the
USB and UMS commands (and possibly others). Since those boards does
not have SD card slots, a recovery serial download is needed at every
update.
This patch make sure that only the separate U-Boot DTB will be
included in the FIT image by using the nodtb variant.
[1] https://source.codeaurora.org/external/imx/imx-mkimage/tree/iMX8M/mkimage_fit_atf.sh?h=rel_imx_4.14.98_2.0.0_ga#n35
[2] https://git.busybox.net/buildroot/tree/package/imx-mkimage/0001-add-support-for-overriding-bl32-and-bl33-not-only-bl.patch?h=2019.11#n42
Signed-off-by: Julien Olivain <juju@cotds.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
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