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LS1012A - system timer issues

Question asked by Andrey Korolyov on Jul 26, 2017
Latest reply on Feb 4, 2019 by Johan Derycke



while working with ls1012a-rdb I`ve observed quite weird behavior possibly related to a system timer instability - one of every few 'dmesg' scroll does stall while I am using ssh connection and in same time performs relatively well within serial console. The first suspected candidate was frequency scaling affecting pfe clock, but fixing SoC CPU frequency didn`t change anything - stalls continued to appear and I tried to dig deeper.


After quick look, it appears that a) system timer monotonicity is changing over time as it does affect TCP connections for local links in a described manner - e.g. system lose a few tcp packets due to timer (?) stall and b) system timer seems to be quite slower than it should be, losing tens of seconds within a few minutes of near-idling with loaded Linux kernel. What is more interesting is that an active Rx/Tx job through pfe interface could significantly push down the variation - the larger a flow bandwidth is, the lower is an observable drift. SDK`s U-Boot 'sleep' execution time also seem to be larger by a *30* percent than known-to-be-good sleep with same argument.


Unfortunately NTP daemon seem to diverge within any sane setting set for drift value, so the issue is a certain candidate for sw/hw fix.  


I am using reference board for LS1012A from NXP with latest SDK 2.0-1703, if this could be related. Any suggestions on the situation improvement are highly welcomed.