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.przyw...@arm.com>
Acked-by: Maxime Ripard <maxime.rip...@free-electrons.com> Thanks, Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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