We have a custom board that's based on the i.MX8M Mini EVK. I noticed that it takes a lot longer for the random number generator to initialize on our board vs the EVK. On the EVK, I get the message "random: crng init done" at about 7 seconds after bootup, but on our board it can take more than 10 minutes. I installed rng-tools and now our board is around the 7 second level too, so we have a workaround.
I'm curious, though, as to what could cause this. Both boards are headless and running a lightly modified version of linux-imx L4.14.98_2.0.0. They have similar accessories attached - same camera, same audio codec etc. Our changes to vs. the EVK were mostly to remove things: ethernet, audio codec, pcie interface, SD card interface to name a few.
Is there any possible straightforward answer to this, or does it really heavily depend on the hardware changes we made?