Pi 5 and NVMe SSD

In February I mentioned getting an Argon NEO 5 NVMe case for my Pi 5.

It was slightly fiddly to put it all together, but not really outside
expectations. Linux was able to see my SSD without any trouble.

However I have not been able to get the Pi to boot directly from the
SSD. It can see there’s something there but can’t interpret it properly;
the diagnostic output (copy-typed) is:

  NVME on 0
  Trying partition: 0
  Unable to read partition as FAT
  type: 32 lba: 0 '' '            ' clusters 0 (0)
  Trying partition: 0
  Unable to read partition as FAT
  type: 32 lba: 0 '' '            ' clusters 0 (0)
  NVME off
  Timeout 00000000 3c303020 00000000 00000000
  nvme: error 8
  Failed to open device: 'nvme'

(Why is there ASCII ‘ 00<’ in the timeout message?)

My solution was to boot from the SD card but to configure it (via
cmdline.txt and /etc/fstab) to mount the root system from the SSD. This
works (and it’s not like the performance & capacity of the firmware
partition is very important) though there are now two points of failure.

My interpretation of all this is that the hardware is connecting the SSD
perfectly well, and the Linux kernel talks to it correctly, but the boot
loader is failing to communicate properly with the SSD.

Based on forum posts there are many compatibility issues between the Pi
5 and NVMe devices, so anyone planning to buy one should do their
research first.

In my case the SSD is a Crucial CT1000P5SSD8; I had it left over from a
decommissioned PC.

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https://www.greenend.org.uk/rjk/