Potential LUKS key lost on Raspberry Pi reboot?

I ran into a weird issue when my Raspberry Pi 4 updated itself. This Pi is setup with a Zymkey in developer mode and a LUKS encrypted system running Ubuntu Server 20. I have the unattended-updates package setup to install security updates and reboot my device. After the reboot, my device would no longer boot up. It prints a single message after the bootloader “Could not get clk -51”. I’ve since reflashed the sd card and it is now working fine.

Now like I said this system is in developer mode. It’s only a testbench and not critical, and the devices that I’ve deployed in production mode have continued to work just fine. I’m just trying to figure out what might have gone wrong and the first big difference between the devices that are working fine and this one is the mode the Zymkey is in. So while I have no clue if the Zymkey was the problem I’d like to ask the question of whether it could have been? Would the Zymkey forget a stored LUKS key if it was in dev mode?


I went through a similar process here for sanity’s sake and I saw a similar message, but after 10 seconds or so the Pi continued on and booted. My upgrade took my kernel to 5.4.0-1015-raspi (20.04, 64 bit).

The message I saw was,
spi-bcm2835 fe204000.spi: could not get clk: -517

I don’t think this is necessarily our problem but if you can verify the exact message text, I can look a little deeper. The message I saw would indicate it’s something in the spi bus driver which we don’t use. Also good to know you have not seen the problem in Production Mode.


I can confirm that I get that same exact message, but I also don’t think that’s the issue as it appears on every one of my devices (including the working ones and ones I haven’t touched). It’s the next messages that should appear that I believe are important which relate to mounting the data partition. Did yours boot up fine then after the kernel upgrade?