Hello All, i'm developing kind of bootloader for R-CAR and need to jump from BL2 to BL33 which my bootloader?other question how Green Hills did it in her bootloader ?Thanks.
Hi mohamed
Sorry to reply late. For the ARM Trusted Firmware, the standard boot flow is as below:
BL1(EL3)->BL2(S-EL1)->BL31 runtime firmware(EL3), then boot optional BL32 image if needed, after then back to BL31, BL31 runtime firmware is the secure monitor to hand over to normal world boot load BL33.
In latest ARM TF, there is the feature of "Running BL2 at EL3 execution level", it looks useful for your usage model:
1.4. Running BL2 at EL3 execution levelSome platforms have a non-TF-A Boot ROM that expects the next boot stage to execute at EL3. On these platforms, TF-A BL1 is a waste of memory as its only purpose is to ensure TF-A BL2 is entered at S-EL1. To avoid this waste, a special mode enables BL2 to execute at EL3, which allows a non-TF-A Boot ROM to load and jump directly to BL2. This mode is selected when the build flag BL2_AT_EL3 is enabled. The main differences in this mode are:
https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/firmware-design.rst
Best Regards
Jett Zhou