[linux-dvb] Re: PCI latency for Aver761 / dvb-bt8xx / FDSRoverflows

[Greg Matthews <gmatt@nerc.ac.uk>]

On Mon, 2004-09-20 at 15:01, Hamish Moffatt wrote:
> I've been having a lot of trouble with FBUS & FDSR interrupts on the
> Avermedia 761 (dvb-bt8xx card). Sometimes I get just one FBUS error
> at a time, which the data sheet indicates is a buffer overflow caused by
> long bus latencies. Usually these correspond to first starting to watch
> live TV or record something in MythTV.

I've had problems with my 761 but I havent diagnosed them to this level.
Occasionally when I start to watch a channel I get period jerky movement
as tho the stream pauses and then catches up continuously. Is this what
you are seeing along with these FBUS errors? esacaping out and tuning in
again (using mythtv here) usually cures this. A recent upgrade to kernel
2.6.9-rc1 and cvs dvb-kernel seemed to make this worse with one channel
(BBC2) unwatchable because of it, ie never cured when "retuning".

> I've been increasing the PCI bus latency timer on the bt878 (audio and
> video sections) gradually to try to kick this problem. I've been running
> with 166 (= ~5478us) for a while and this still happens. I've just
> increased it to 192 (~6336us) to see if that helps. 

Can you explain exactly how you tweak the latency - is this in the BIOS?
If I can play with this then I can hopefully add some more data to the
problem.

GREG

> Thanks
> 
> Hamish
-- 
Greg Matthews
iTSS Wallingford	01491 692445