Bug 217882

Summary: AMD Geode LX hardware RNG driver produces regular patterns (geode-rng.c)
Product: Drivers Reporter: Timur I. Davletshin (timur.davletshin)
Component: OtherAssignee: drivers_other
Status: NEW ---    
Severity: normal CC: bagasdotme, jonas.gorski
Priority: P3    
Hardware: i386   
OS: Linux   
Kernel Version: 5.15 Subsystem:
Regression: Yes Bisected commit-id:

Description Timur I. Davletshin 2023-09-07 09:37:48 UTC
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.
Comment 1 Timur I. Davletshin 2023-09-07 11:46:57 UTC
https://github.com/openwrt/openwrt/issues/13417 - original report (OpenWrt).
Comment 2 Artem S. Tashkinov 2023-09-07 12:43:37 UTC
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
Comment 3 Bagas Sanjaya 2023-09-08 00:48:05 UTC
And also, please try latest mainline to confirm this regression still exists.
Comment 4 Jonas Gorski 2023-09-10 08:48:41 UTC
After identifying the breakage and verifying the fix, I submitted a patch for the issue (https://patchwork.kernel.org/project/linux-crypto/patch/20230910083418.8990-1-jonas.gorski@gmail.com/).