[coreboot] [PATCH] artecgroup/dbe62: Route ethernet adapter IRQ correctly and reduce interrupt contention problems by using different IRQs for all the interrupt lines

Tom Sylla tsylla at gmail.com
Sun May 4 22:14:07 CEST 2008

Peter Stuge wrote:
> 32663C_lx_gx_pciconfig.pdf page 46-49 seems to suggest that USB is
> always on INTD# IRQ11. This could be hardwired in LX/5536; GL packets
> from USB will always trigger IRQ11. Or worse they will always trigger
> PCI_INTD# meaning a well-designed board with 4 PCI slots, or a badly
> designed board with less slots will always need to share somewhere.

Just to clear up a few confusions in this thread:

Nothing is hard-wired, not even the INTD for USB. All of the interrupt 
routing in 5536 is configured in the IRQ mapper in the MDD. See section 
5.8 of the 5536 datasheet. USB is just input 2 to the unrestricted Y 
mapper. Lots of other southbridges have similar second-level PIC mappers 
(XPICs, etc) for their on-board devices.

The "linkage" to INTD is done in VSA:


(note the Int Line value in that code is a flag for later:

As said later in this thread, USB needs to be a well-behaved PCI device 
and needs a Int Pin and Int Line. When the PCI config space for LX/5536 
was defined, we had to pick a pin for the internal devices. VSA (config 
space) has to have something defined. That was INTD for USB (similarly 
INTB for audio). USB just gets stuck with whatever Int Line goes with INTD.


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