You can go from aarch64 execution state to aarch32 without resetting the core by using the correct ERET instruction. In order to go from aarch32 to aarch64, the reset management register can be used. However, it does have caveats.

I intend to start some bare metal development on the RPI3. Where can I find some information about the boot sequence and the memory map/data sheet of BCM2837? Are these aspects of the chipset the same as on RPI2?

Thanks! that helps.

What is the mechanism for releasing the CPUs from reset in aarch64 instead of the aarch32 execution state on the RPI3? Is there a configuration input or does one have to rely on the RMR_EL3 to switch from aarch32 to aarch64? This would be the first step to run any aarch64 code. Alternatively, is it ...