Re: IRQ routing / assignment issue

From: Robert Hancock
Date: Mon Sep 01 2008 - 13:21:26 EST


Radu Rendec wrote:
Hi,

I'm trying to make the kernel assign different irqs for two NICs
connected to _separate_ pci buses. Messing around with pirq= kenrel
parameter didn't seem to change anything.

The kernel doesn't really have any way to change the physical device/slot to IRQ mapping. In some cases there are BIOS settings which might influence this, but in most cases it's impossible to change (i.e. devices physically wired to the same IRQ line).


The machine is a smp (dual-xeon). Relevant lspci output is:
01:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5721
Gigabit Ethernet PCI Express (rev 11)
02:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5721
Gigabit Ethernet PCI Express (rev 11)

IRQ assignment dmesg output is:
ACPI: PCI Interrupt 0000:01:00.0[A] -> GSI 16 (level, low) -> IRQ 16
ACPI: PCI Interrupt 0000:02:00.0[A] -> GSI 16 (level, low) -> IRQ 16

At the moment I'm almost clueless about how irq routing / assignment
works (either in general or in linux), so any suggestion would help -
even "rtfm" would be helpful, as long as you specify what is the
appropriate manual ;)

If you are so kind to reply, please include my address in cc (I'm not
subscribed).

Thanks,

Radu Rendec


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