Re: [PATCH 2/2] PCI: Add quirk to disable PCIe port services on Sophgo SG2042

On Sat, May 02, 2026 at 09:58:04PM +0800, Icenowy Zheng wrote:
> The problem is that the MSI controller has only 16 MSIs usable (it's
> wrongly described as 32 previously, a fix to this is pending[1]), and
> the failing device have an onboard PCIe switch, which created many PCIe
> ports (and corresponding pcieport devices).

Is the SG2042 only used in that single product?  If it is used in other
products which do not have an on-board PCIe switch, why do you want to
disable MSIs on those other products as well?

My point is, you want to constrain this to a specific product, not to
the SoC.  Can you maybe solve this by not specifying interrupts in the
devicetree for the PCIe switch?

> With pcieport devices activated, 11 MSIs are requested by the pcieport
> drivers -- 3 SoC PCIe ports and 8 switch downstream ports. Then only 5
> MSIs are available, but there're still 10 downstream-facing PCIe ports
> now (and 5 of them are hardwired to onboard peripherals).

pcieport can make do with a single MSI vector because all port services
support a shared interrupt.  But I assume your point is that this
particular product has so many PCIe ports that you're still close
to the 16 MSIs limit?

Thanks,

Lukas