Mathias

Thanks all for your help! So, to keep for the record:
 
0) before you play around with a new kernel, make sure you have a backup of /boot (I keep such a backup as /boot_bak directly on the system). Worst case, flash a new image on a usb stick and grab its /boot
 
1) in order to rescue a system where a new kernel does not boot:
     * in /boot, there are 3 symbolic links that must point to the right place: dtb, Image and uInitrd. The last two must point to the same version. For example, dtb -> dtb-4.4.174-rockchip64, Image -> vmlinuz-4.4.174-rockchip64, uInitrd -> uInitrd-4.4.174-rockchip64 (I could not find any version other than 4.4.174 for the dtb, so I've always kept the link pointing to it);
    * of course, you still need config-4.4.174-rockchip64, System.map-4.4.174-rockchip64 and your kernel, for example vmlinuz-4.4.174-rockchip64
    * you can keep several kernel version, just adjust the three symlinks mentioned above to point to the version you want to use for your next boot;
    * All these steps can obviously be done by mounting your sdcard or emmc on your computer.
 
2) Then boot/reboot your system
     * keep in mind that the rockpro64 is very unreliable when it's about starting... if the system does not boot, check if the ethernet leds came up or not, if the power led came up or not, etc Mine often does not even get the power led turning on! So try several time to press the power and/or reset buttons, plugin in/unplugging before you give up;
     * some kernels do not support hdmi output yet (actually, most of them beside the Rockship original patches). So don't despair if nothing comes on the screen... If you've added a dptx.bin firmware, it can be that the board does not boot if no screen is connected...
 
So far, I could not boot with the Armbian 4.20.0 kernels but everything works fine with the Ayufan kernels installed on Armbian (both 4.19 and 5.0 ). In this case, just copy the deb package from Ayufan that you want and install it with dpkg (dpkg -i {package name}). You will have to redo one of the mentioned symlinks, but other than that, everything works.
 
Mathias

sudo nano /etc/hdparm.conf
#Disk1 /dev/disk/by-id/ata-YOURDISK { # mult_sect_io = 16 # write_cache = off # dma = on spindown_time = 240 } #Disk2 /dev/disk/by-id/ata-YOURDISK { # mult_sect_io = 16 # write_cache = off # dma = on spindown_time = 240 } 240 = 20mins - It works at my setup, i did't try lower spindown time.
 
Some drives can bee spun down with hd-idle. change HD_IDLE_OPTS value, then start and activate hd-idle.service. let me know if it works. Thanks.

@IgorThanks! Now I need to deliver... :-)
 
@chweNo, I'm using a "noname" enclosure that is based around the JMS578. But again, it just works great when connected to my laptop (with Debian Buster) and always makes trouble on the RockPro. I wanted to make sure this is not a problem with power, so I used a 6A power supply (universal power supply designed for laptops) and got the same trouble. But I'll try again with this power supply and the "stable" 4.4 kernel and either come back with a big smile on my face or with a backtrace...