On Mon, Jun 10, 2024 at 07:29:15PM +0000, Joel Holdsworth wrote: > Hi Stafford, thanks for your response. > > > - You sent this 2 times, is the only change in v2 the sender address? > > Yes, I was just having some difficulty with Git and SMTP. Should be fixed now.
OK. > >> In the existing design, TTCR is prone to undercounting when running in > >> continuous mode. This manifests as a timer interrupt appearing to > >> trigger a few cycles prior to the deadline set in SPR_TTMR_TP. > > > This is a good find, I have noticed the timer is off when running on > > OpenRISC > > but never tracked it down to this undercounting issue. I also notice > > unexplained RCU stalls when running in Linux when tere is no load, this > > timer > issue might be related. > > > Did you notice this via other system symptoms when running OpenRISC or just > > via > > code auditing of QEMU? > > I'm working on an OpenRISC port of Zephyr. The under-counting issue causes > consistent deadlocks in my experiments with the test suite. I wouldn't be > surprised if it causes problems for other OS's. Thats cool. I got around to testing the patch with Linux, unfortunately I didnt see an improvement in the lockups I have been seeing during boot time. But I am sure this is a step in the right direction. > > In QEMU there is a function clock_ns_to_ticks(). Could this maybe be used > > instead to give us more standard fix? > > Seems like a good idea, and I now have some nearly-complete patch that brings > hw/openrisc/cputimer.c into closer alignment with > target/mips/sysemu/cp0_timer.c. Hi, I was waiting for this second version patch, v2. Have you ever completed it? > However, don't we run into problems with undercounting with clock_ns_to_ticks, > because if I understand correctly it will round ticks down, not up?, which is > the problem I was trying to avoid in the first place. You might be right, but if that is the case maybe it's a but to raise to the maintainers directly. I was planning to look into this more cosely after you sent the followup patch. -Stafford
