[linux-audio-user] Re: Linux IRQ datapoint

[Mark Knecht]

Lee Revell wrote:
> On Mon, 2004-10-11 at 16:59, Mark Knecht wrote:
> 
>>I was building a new kernel under FC2 this morning trying to make FC2
>>equal to my Gentoo kernel which is working very well. I made a mistake
>>on this new kernel and forgot to turn on 'APIC contoller for UMP
>>machines'. When the kernel booted I got all sorts of xruns. The IRQ
>>was threaded, so I set it for non-threaded but still got a lot of
>>xruns. (>100 in 10 minutes)
>>
>>I rebuilt the kernel where the only change I made was to enable APIC
>>interrupts and IO-APIC controllers for UMP. The kernel booted and has
>>been running for 30 minutes with no xruns...
>>
>>Just another IRQ datapoint, but that was the only change I made... 
>>
> 
> 
> That is really weird, most people report better results _disabling_ APIC
> on UP.
> 
> Lee
> 
> 
Who knows?!? I just take data. I don't interpret it! ;-)

Could be specific to this ATI chipset's interrupt controller for all I 
know. I built a similar kernel yesterday, also under FC2, but on my 
older Via KT266 MB with an Athlon XP (I think...) 1600+. That MB only 
supports legacy style interrupts and the kernel worked fine, at least at 
-p64/-n2 using an HDSP 9652 sound card.

I did find two strange things about that setup, both sound card related 
I think:

1) The HDSP driver would not allow me to even try and set -p <64. Just 
told me it wasn't allowed. This may be by design. Possibly the way it 
moves DMA data it just doesn't support less than that.

2) There are two 'regions' of sample rates with that card

- 32K, 44.1K & 48K (i.e. - 1x)
- 64K, 88.2K & 96K (i.e. - 2x)

If I try to change from any 1x sample rate to any 2 x sample rate using 
Jack I get a message that it cannot do it. Parameters not defined or not 
available IIRC. Same going from 2x to 1x.

However, if I use hdspconf and manually shift from 44.1K (1x) to say 96K 
(2x) hdspconf reports that it changed. I can then use Jack to change 
between all 2x rates, but I cannot go back to 1x. To go back to 1x I 
have to once again use hdspconf. Sounds like a driver issue to me, but 
who knows. (I'm not supposed to interpret!) ;-)

- Mark