System: Alix board 2d13 (AMD Geode LX800) running OpenWrt 23.05.0-rc3 (kernel 5.15.127)
Steps to reproduce:
cat /dev/hwrng and see output. Output in console shows regular pattern, rngd daemon (from rng-tools) refuses to run because of low entropy from /dev/hwrng. Pattern doesn't change until I reboot system.
Important notice: This problem started somewhere between 4.14.267 (kernel used in OpenWrt 19.07.9) and my current 5.15.127.
OpenWrt developers recommended addressing this problem upstream since they did not alter this driver in any way.
https://github.com/openwrt/openwrt/issues/13417 - original report (OpenWrt).
Without git bisect it's highly unlikely this bug report will be acted upon. I understand it's gonna be hard to carry it out but you can cross compile on a different device to speed up the process: https://docs.kernel.org/admin-guide/bug-bisect.html
And also, please try latest mainline to confirm this regression still exists.
After identifying the breakage and verifying the fix, I submitted a patch for the issue (https://firstname.lastname@example.org/).