I am studying the Chinese processor rk3568 (armv8 cortex a55 4 cores) I found some information on how to run the second core. To do this, I use the PSCI interface from arm itself. I have a small test project in Aarch64 mode, which essentially does almost nothing (either blinks an LED or sends a message via uart). I am assembling two firmware (bin file) from it, the first firmware for core 0, which sends a message via Uart and includes core1. The second firmware blinks with an LED. Everything is working as expected. But when I try to pull the same trick from aarch32 (i.e. core 0 core in aarch32 sends CPU_ON command to core 1, which should run the code in aarch64) the second core does not start. At the same time, CPU_ON returns 0 (success), and when resending it returns -5 (pending_on). That is, the kernel tries to start, but it freezes somewhere. Although it looks like it hasn't started executing any instructions from my code yet.