[linux-dvb] Re: [PATCH] fix for stream corruption on budget / Nova-T cards

[Emard <emard@softhome.net>]

On Sun, Aug 31, 2003 at 06:40:04PM +0100, Jon Burgess wrote:
> Emard wrote:
> 
> >This DMA corruption has been there long time around.
> >We tried to fix it with many tweaks, that's the reason of
> >vpeirq introduction but from your experience it seems some 
> >data loss hole still remained open.
> 
> What was done before vpeirq? How far back in the code do I need to look 
> to find this?

Before March or so, the code is dirty and pure junk which
easily can miss DMA at PCI latency. It can work well on some
machines but PCI latency should be well tuned.

The source or the problem was blamed on separate vsync detection 
chip found mostly on budget cards. This chip and 7146 can have 
slightly different timing of vsync and therefrom came the DMA blocks
missing in the previous code. 

It could be that metzlerbro's are still using this type of 
code in their DVB drivers

vpeirq() doesn't need to trigger on the vsync chip signal and is 
much better solution invented by a czech developer who had 3 budget 
cards downloading simultaneousy and had missed DMA interrupts 
which vpeirq() completely solved.

I was using it on 2 budget cards simultaneous cards and worked fine
for me too.

Emard


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