I am running armbian buster Armbian_5.91_Rockpro64_Debian_buster_default_4.4.184_desktop.img.

I need rt_preempt in order to run linuxcnc.
I started with the 5.0.21.tar.gz kernel source from <https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/> and the rt_preempt patch 5.0.21-rt16.patch.gz from <https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/>. I applied the patch to the kernel source and compiled it on a 4gb RockPro64. It boots fine into a remote terminal using ssh but there is no display on my HDMI monitor.  The white LED is showing but the red LED is not lit.

 

I had an earlier version of linux-5.0-rt running on armbian stretch so I mistakenly thought this would be a walk in the park.

 

Any ideas where to start looking?

 

Alan

5 hours ago, acondit said:

Any ideas where to start looking?

Yes. Use Armbian build system and add RT patches to either default 4.4.y or DEV 5.3.y. That is probably your only way and add patches is not always straightforward. Kernels from other sources (especially official mainline) might not just work - support for RK3399 is poor. Even for DEV we can't be sure for each upgrade that its working well. Note: currently it takes some time before HDMI is switched on, but it works.

 

https://github.com/armbian

https://docs.armbian.com/Developer-Guide_Build-Preparation/

linux-5.2.10 is the latest kernel for which there is an -rt patch. I have previously had problems with 4.4 being horribly slow under rt_preempt.

 

I was able to build the linux-5.2.14-rt7 kernel and replace the linux-4.4.184-rockchip64 kernel on the Armbian_5.91_Rockpro64_Debian_buster_default_4.4.184_desktop.7z image and it appears to be working fine.