plat: imx8mm: Add in BL2 with FIP
Adds bl2 with FIP to the build required for mbed Linux booting where
we do:
BootROM -> SPL -> BL2 -> OPTEE -> u-boot
If NEED_BL2 is specified then BL2 will be built and BL31 will have
its address range modified upwards to accommodate. BL31 must be
loaded from a FIP in this case.
If NEED_BL2 is not specified then the current BL31 boot flow is
unaffected and u-boot SPL will load and execute BL31 directly.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
Change-Id: I655343b3b689b1fc57cfbedda4d3dc2fbd549a96
diff --git a/docs/plat/imx8m.rst b/docs/plat/imx8m.rst
index f184b69..0408730 100644
--- a/docs/plat/imx8m.rst
+++ b/docs/plat/imx8m.rst
@@ -43,3 +43,17 @@
used to generate flash.bin, and flash.bin needs to be flashed into SD card
with certain offset for BOOT ROM. the u-boot and imx-mkimage will be upstreamed
soon, this doc will be updated once they are ready, and the link will be posted.
+
+TBBR Boot Sequence
+------------------
+
+When setting NEED_BL2=1 on imx8mm. We support an alternative way of
+boot sequence to support TBBR.
+
+Bootrom --> SPL --> BL2 --> BL31 --> BL33(u-boot with UEFI) --> grub
+
+This helps us to fulfill the SystemReady EBBR standard.
+BL2 will be in the FIT image and SPL will verify it.
+All of the BL3x will be put in the FIP image. BL2 will verify them.
+In U-boot we turn on the UEFI secure boot features so it can verify
+grub. And we use grub to verify linux kernel.