On Sunday 20 August 2006 17:09, John Drescher wrote:
> > Hi again Michael, Rey, List
> >
> > I'm very happy to say that since my previous posting (almost 2
> > weeks ago), I've not seen a new dma error. I've increased my
> > grabbing-schedule from ~-1.5 hours a day to ~17h a day to for this
> > whole test, and the only change I have made is disabling the
> > cpuspeed service.
> >
> > I do note that Michael still is experiencing the problem, so it is
> > possible that changing the cpu frequency in mid-DMA is only one of
> > the cause that can lead to this problem.
> >
> > I have now loaded the powernow-k8 module on my system and will run
> > with it loaded (not cpuspeed running) for a while, and then write
> > my own manager to quickly toggle CPU frequencies to see if that
> > reliably introduces the DMA-error.
>
> Just wanted to say that I have a dual processor Opteron 850 system,
> running powernowd and I have not seen this problem. I am running
> amd64 under gentoo linux with a 1.6.17 kernel and ivtv 0.7.0 with a
> hauppage pvr500.
I've finally managed to reproduce the DMA error reliably and quickly
using the following shell script on my dual AMD:
#!/bin/sh
cd /sys/devices/system/cpu
echo userspace >cpu0/cpufreq/scaling_governor
echo userspace >cpu1/cpufreq/scaling_governor
while true; do \
echo 2200000 >cpu0/cpufreq/scaling_setspeed; \
echo 2200000 >cpu1/cpufreq/scaling_setspeed; \
sleep 0.3; \
echo 1000000 >cpu0/cpufreq/scaling_setspeed; \
echo 1000000 >cpu1/cpufreq/scaling_setspeed; \
sleep 0.3; \
done
For some reason powernowd triggers the bug only very rarely, but this
shell script is very effective.
As I suspected it is a particularly nasty bug with no obvious solution
as yet. I only hope that it isn't a DMA hardware bug of the MPEG chip.
Apparently the DMA engine of the chip isn't the most reliable. Anyway,
now that I can reproduce it I can finally do some serious
investigation.
Hans
_______________________________________________
ivtv-devel mailing list
[email protected]
http://ivtvdriver.org/mailman/listinfo/ivtv-devel
