Adding an interrupt to a PCI device via an ACPI entry

Adding an interrupt to a PCI device via an ACPI entry

[Chris Packham]

Hi All,

Is there a way to add information about a PCI device via an ACPI entry? 
I'm trying to deal with a device that has an erratum where regular PCI-e 
MSI interrupts don't work. The workaround is to connect a dedicated INT 
output line to an interrupt input on the board. The hardware design has 
done this but I'm trying to figure out how to make that work with ACPI 
describing the hardware.

I know in devicetree land I can do this with something like

&pcic {
                 mydevice@1,0 {
                         compatible = "pci1234,5678";
                         reg = <0x00000000 0 0 0 0>;
                         interrupt-parent = <&intc>;
                         interrupts = <1 IRQ_TYPE_LEVEL_LOW>;
                 };
};

And then when my driver is bound to device the usual irq resource stuff 
will give me the right interrupt line.

Is there a way of expressing this kind of thing in ACPI?

Thanks,
Chris

Re: Adding an interrupt to a PCI device via an ACPI entry

[Chris Packham]

On 13/03/24 09:28, Chris Packham wrote:
> Hi All,
>
> Is there a way to add information about a PCI device via an ACPI 
> entry? I'm trying to deal with a device that has an erratum where 
> regular PCI-e MSI interrupts don't work. The workaround is to connect 
> a dedicated INT output line to an interrupt input on the board. The 
> hardware design has done this but I'm trying to figure out how to make 
> that work with ACPI describing the hardware.
>
> I know in devicetree land I can do this with something like
>
> &pcic {
>                 mydevice@1,0 {
>                         compatible = "pci1234,5678";
>                         reg = <0x00000000 0 0 0 0>;
>                         interrupt-parent = <&intc>;
>                         interrupts = <1 IRQ_TYPE_LEVEL_LOW>;
>                 };
> };
>
> And then when my driver is bound to device the usual irq resource 
> stuff will give me the right interrupt line.
>
> Is there a way of expressing this kind of thing in ACPI?

Looking at 
https://www.kernel.org/doc/html/latest/firmware-guide/acpi/enumeration.html#pci-hierarchy-representation 
seems promising.