PCIe interrupts in the device tree

[Johns Daniel]

On Tue, Mar 24, 2009 at 3:54 PM, Kumar Gala <galak at kernel.crashing.org>wrote:

>
> 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.
>

When you say "wired", do you mean hard-wired?
If so, how would you specify and use INTx message interrupts?


>
>
>  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
>
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