[U-Boot] [PATCH v15 07/10] arm64: core support

[FengHua]

hi bhupesh,

> Hi David,
>
> In reference to my mail above, I see that the transition to EL2 (from EL3) which occurs very early
> in start.S needs to be changed on lines of the ARMv7 code, i.e. the EL2 transition should happen just
> before Linux is booted up by the u-boot.
> 
> The reason for the same is that a no of ARM IPs like GIC, SMMU and TZPC/TZASC need to be configured to
> allow non-secure accesses from Linux world (which runs in EL1 mode). Adding the assembly code for all
> such IPs in 'setup_el3' function in start.S, will bloat the start.S and also increase the chances of a
> bug in the assembly code.
> 
> Hence, I would like to propose a strategy to shift from EL3 to EL2 to some point in u-boot code after the
> C Run Time has been initialized (similar to present ARMv7 u-boot code). 
> 
> If you are ok with the same, I can try to send out some RFC patches rebased against your latest v16 code-base.
> 
> Please let me know.
> Regards,
> Bhupesh
> 
Actually, patch v16 did exception level switch in the way as you said. please review the code.
Both master and slaves switch to el2(el1) just before jumping to linux kernel. BTW,if any good conception please feel free to patch it.

Best wishes,
David