PCIe interrupts in the device tree

[Kumar Gala]

On Mar 24, 2009, at 3:24 PM, Johns Daniel wrote:

> Could somebody please explain the declaration of the PCIe interrupts
> in the device tree?
>
> I was under the impression that PCIe interrupts in the PowerPC Linux
> kernel default to using INTx signaling (vs. external IRQ pin assertion
> and MSI signaling). Am I right?
>
> If so, then do the interrupt-map lines in the DTS refer to the
> internal IRQ used by Freescale processors to implement INTx virtual
> wire interrupts?
>
> For example, in the mpc8536ds.dts file, under "pci1: pcie at ffe09000"  
> we have:
> 		interrupt-map = <
> 			/* IDSEL 0x0 */
> 			0000 0 0 1 &mpic 4 1
> 			0000 0 0 2 &mpic 5 1
> 			0000 0 0 3 &mpic 6 1
> 			0000 0 0 4 &mpic 7 1
> 			>;
> Are the 4, 5, 6, and 7 internal or external IRQs?

The .dts and linux make no distinction between internal & external  
IRQs.  This is a silly artifact of Freescale UMs.  IRQ 0 starts at  
offset 0x50000 and each 0x20 offset is another IRQ.  So typically  
External 0 == IRQ0, Internal 0 == IRQ16.

So this says that Ext 4, 5, 6, 7 and wired to INTA, INTB, INTC, INTD  
for this particular PCIe controller.

> And the "msi at 41600" section in the same mpc8536ds.dts file does NOT
> affect PCIe interrupts unless a driver calls pci_enable_msi()?

correct.

- k