Hello Experts,
I need to operate a custom app at EL3 on a Cortex-A53 core running on the i.MX8 based platform. The bootflow shows me that a hand-off from ATF (BL31) to U-boot (BL33) is where the transition from EL3 to EL2 occurs for Uboot and it stays at EL2.
Can anyone suggest a procedure or mechanism to keep the Uboot and custom apps running at EL3? Are there any examples ?
Thanks in advance.
I'm afraid I can't answer specifically for the i.MX8, but I suspect you'd need is a custom ATF image.
But a more basic question - what is it that you want to run at EL3 and why does it need to be at EL3?EL3 is usually firmware and Security state switching code, so small and tightly focussed. I wouldn't expect to see apps, or anything like uboot, at EL3.
If what you need access to is Secure state/PA space, why not target S_EL0/1?
Thanks for the reply. The EL3 requirement is imposed by the BSP vendor supplying the RTOS. At this time the purpose is not clear. Currently, I can see U-boot operating after BL31 handoff at EL2.
Can you suggest what can be customized in BL31 (ATF) for initial experiments?
I tried some mods to BL31 code to avoid the EL2 setup but that appears to fail.
Hi,
There seem to be a way in TF-A to boot an el3 payload instead of BL31.
Best regards,
Vincent.