On Mon, Dec 19, 2016 at 01:50:02AM +0000, Andre Przywara wrote:
The Allwinner A64 SoC starts execution in AArch32 mode, and both the boot ROM and Allwinner's boot0 keep running in this mode. So U-Boot gets entered in 32-bit, although we want it to run in AArch64.
By using a "magic" instruction, which happens to be an almost-NOP in AArch64 and a branch in AArch32, we differentiate between being entered in 64-bit or 32-bit mode. If in 64-bit mode, we proceed with the branch to reset, but in 32-bit mode we trigger an RMR write to bring the core into AArch64/EL3 and re-enter U-Boot at CONFIG_SYS_TEXT_BASE. This allows a 64-bit U-Boot to be both entered in 32 and 64-bit mode, so we can use the same start code for the SPL and the U-Boot proper.
We use the existing custom header (boot0.h) functionality, but restrict the existing boot0 header reservation to the non-SPL build now. A SPL wouldn't need such header anyway. This allows to have both options defined and lets us use one for the SPL and the other for U-Boot proper.
Also add arch/arm/mach-sunxi/rmr_switch.S, which contains the original ARM assembly code and instructions how to re-generate the encoded version.
Signed-off-by: Andre Przywara andre.przywara@arm.com
Acked-by: Maxime Ripard maxime.ripard@free-electrons.com
Thanks, Maxime