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

[Andreas Vierengel <vdr@vierengel.de>]

Am So, 2003-08-31 um 18.28 schrieb Jon Burgess:
> Andreas Vierengel wrote:
> 
> 
> > hi,
> > your patch doesn't work for me (P4-Celeron 2.4GHz, i845GE Chipset).
> > sorry !
> > However I tested all combinations of burst and treshold settings for
> > Video-DMA-Channel #3 in PCI_BT_V1. Results are below.
> > However I actually do get stream corruption on my Nexus-s as well, but
> > they are very rare. So I applied the same burst/treshold settings to my
> > nexus-s as well. Things are now perfect on both cards, but as Jon said:
> > "this only indirectly avoids the problem and doesn't actually fix it."
> 
> [ Results from a good set of test deleted to save space ]
> 
> It is good that you can get it to work well. You results imply that 
> increasing the threshold does seem to make it work better for you.
> 
> I might have been simplifying the "burst size" issue a bit too much. 
> There may well be issues with doing big bursts on the bus.
> 
> Do you use the built video of the 845G?

yes.

> 
> I would be interested to know how the shared memory of the 845G video 
> effects the PCI bus. The PCI bus must get interrupted frequently as the 
> video chip refills the display FIFO.

the vga-chip seems to be on bus 0. only onboard ethernet is on bus 1
together with all external pci-cards. here is a lspci output. I don't
know very much about today's motherboard internals, but are these 2
busses are physically seperate ?

00:00.0 Host bridge: Intel Corp.: Unknown device 2560 (rev 03)
00:02.0 VGA compatible controller: Intel Corp.: Unknown device 2562 (rev
03)
00:1e.0 PCI bridge: Intel Corp. 82820 820 (Camino 2) Chipset PCI (rev
82)
00:1f.0 ISA bridge: Intel Corp.: Unknown device 24c0 (rev 02)
00:1f.1 IDE interface: Intel Corp.: Unknown device 24cb (rev 02)
00:1f.3 SMBus: Intel Corp.: Unknown device 24c3 (rev 02)
01:00.0 Multimedia controller: Philips Semiconductors SAA7146 (rev 01)
01:04.0 Multimedia controller: Philips Semiconductors SAA7146 (rev 01)
01:08.0 Ethernet controller: Intel Corp.: Unknown device 103a (rev 82)


> A PCI bus analyzer would be needed to really understand what is going on.
> 
> 	Jon
> 

that would be really cool and certainly a nice addon to strace, tcpdump,
etc :)

--Andi







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