[mythtv] pvr-350 decode stops working
ryan patterson
ryan.goat at gmail.com
Sat Dec 23 16:56:46 UTC 2006
Thanks for the response. You gave me an idea. At the same time as my
software upgrade I think I also changed a few settings in the BIOS setup. I
think I turned on the "spread spectrum clock" option. I'll disable that and
see if my errors disappear.
On 12/23/06, Daniel Staaf <dst at bostream.nu> wrote:
>
> ryan patterson wrote:
> > Dec 22 21:34:00 mythtv kernel: ivtv0-osd warning: DMA xfer from
> > b7b0d808 of 65536 bytes failed with (-5) offset = 0x141800, total
> > 1382400
> >
> > Is DMA the root cause of this failure? If so what particular setting
> > could be causing DMA to act up? The hardware use to be rock solid
> > for three months with no reboot.
>
> The root cause seems to be a design glitch in the DMA engine of the
> CX23415 chip (the MPEG2 encoder/decoder chip on the PVR-350 with an
> embedded Java interpreter), thus making it very hard to write a driver
> that can keep the PVR-350 functioning correctly for a long time with the
> less than perfect hardware found on consumer quality motherboards. The
> firmware (the Java byte-code) is probably buggy too.
>
> The good news is that Hans Verkuil seems to be on top of things and
> hopefully the driver will be as stable as it can be when it is
> completely merged with upstream v4l sometime next year. He's not there
> yet though and I'm a bit worried about what he writes in
> http://www.gossamer-threads.com/lists/ivtv/devel/33614. Apparently the
> PVR-500 uses a PCI-bridge to isolate the cx23416 chips from any signal
> interference on the main PCI bus. That could mean that even Hauppauge's
> engineers with full access to the hardware specs (but maybe not the
> source code to the chip firmware) had so much trouble with writing a
> stable (Windows) driver that they chose to implement a hardware
> workaround for the newer cards.
>
> If you are running any kind of CPU frequency scaling, try turning it off
> as such power saving features may increase the stress on your
> motherboard capacitors and if they are of low quality the interference
> on the PCI bus may increase, leading to more DMA errors (some of which
> the PVR-350 obviously can not handle correctly). Maybe the newer Linux
> kernels enables more power saving features on your motherboard (like
> letting some board components sleep when not in use) or perhaps the
> "cleanups" of the different kernel subsystems has changed the timing of
> events enough to cause the PVR-350 to lock up.
>
> Other things to check is that you have sufficient cooling (the PVR-350
> draws a lot of power, overheating is often first noticed as audio
> glitches in recordings) and a stable power supply (Morex is crap, I have
> a DC-DC converter that I had to replace four capacitors on since they
> started leaking after two years (green, noname ones from Taiwan with the
> electrolyte probably made according to that stolen Japanese recipe that
> turned out to be incomplete).
>
> / Daniel
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--
_____________
Ryan Patterson
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