RTnet and PCI Interrupt Conflicts

[Marc Kleine-Budde]

On Thu, 7 Nov 2002, Jennings, Richard R wrote:

> I have successfully installed RTnet-0.2.6 on two PCs, but I am having
> some problems with my third install.  It seems that the RTnet NIC is
> having an IRQ conflict with the non-RT NIC (and an analog in card - but
> we are not using interrupts in our driver).  I can load all the RTnet
> modules,
> but the system locks up shortly after doing the "rtifconfig eth1 up...".
What happens if you try to load the normal linux drivers? Maybe the driver
itself does not support IRQ sharing, or your analog card doesn't...

> I was able to verify it is the IRQ conflict causing the problem.  Removing
> the non-RT interrupt source fixed the problem.  This brings up three
> questions specifically relating to the PCI bus.

> 1) Can multiple RT devices share interrupts?  Is there an example?
>     (I know PCI boards can share the 4 PCI interrupt pins A-D, but
>      I mean the x86 interrupt lines 0-15)
Hmm..don't know. In general it's not good to share IRQs, due to latency.

> 2) Are there any methods of separating RT and non-RT interrupt lines?
>     (My BIOS is not very cooperative and I have tried all three settings
>      in the Linux kernel on PCI PnP (Any, Direct, and BIOS) without
>      much success)  Any pointers to code examples would be great.
If your bios does not support assigning interrupts to PCI slots, then have
a look in your board's manual. In my Asus manual is written which PCI slot
uses which IRQ, and wich other components share IRQs. Try to find
a adequate order of your PCI cards.

Hope that helps...Marc

-- 
RTnet: http://www.rts.uni-hannover.de/rtnet/