Hello Lukasz, Aleksandr,<br /><br />I have not managed to build it for Rpi4-64. I followed the same approach as Aleksandr but it does not work for 64bit system. <br /><br />Doing exactly the same changes as Aleksandr if I build for MACHINE = "raspberrypi4-64" in local.conf, the .config file has following configs:<br />CONFIG_HAVE_PREEMPT_LAZY=y<br />CONFIG_PREEMPT_NONE=y<br /># CONFIG_PREEMPT_VOLUNTARY is not set<br /># CONFIG_PREEMPT is not set<br /><br />If in the local.conf I replace the machine to MACHINE = "raspberrypi4" and I bitbake again, the .config file looks as follow:<br />CONFIG_HAVE_PREEMPT_LAZY=y<br />CONFIG_PREEMPT_LAZY=y<br /># CONFIG_PREEMPT_NONE is not set<br /># CONFIG_PREEMPT_VOLUNTARY is not set<br /># CONFIG_PREEMPT is not set<br />CONFIG_PREEMPT_RT=y<br />CONFIG_PREEMPT_COUNT=y<br />CONFIG_PREEMPTION=y<br /><br />So for raspberrypi4 the RT kernel is built whereas for raspberrypi4-64 a non preemptive kernel is built (without adding rt.cfg or the patch a PREEMPTIVE kernel will be built, i.e. CONFIG_PREEMPT=y is set in the .config file).<br /><br />Once I figure out why this happens I will post it here. Any further hints are appreciated.<br /><br />Best Regards,<br />Carles