Re: [PATCH] PCI: dwc: ep: Cache MSI outbound iATU mapping

[Niklas Cassel <cassel@kernel.org>]

On 22 December 2025 09:42:50 CET, Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com> wrote:
>> I guess we will need to come up with something else for the MSI-X case.
>> 
>> 
>>> Use the MSIX doorbell method which will not use iATU at all,
>>> dw_pcie_ep_raise_msix_irq_doorbell().
>> AFAICT, right now, the only driver ever calling this function is:
>> drivers/pci/controller/dwc/pci-layerscape-ep.c
>> 
>> Are you suggesting that we somehow change all the other DWC based EPC
>> drivers' .raise_irq() callback to call dw_pcie_ep_raise_msix_irq_doorbell()
>> instead of dw_pcie_ep_raise_msix_irq() for case PCI_IRQ_MSIX ?
>Yes.
>> That sounds like a big change that would need to be tested and verified
>> for each DWC based EPC driver.
>I agree, but this will be clean solution to avoid iATU for MSIX.

I agree that this sounds like a nice solution for those platforms that can use it.

But, for platforms that might not be able to use this method (not sure if this is possible with all versions of the DWC core),
we probably still need to come up with some other solution to this problem.

It would also be nice with some solution that can be used until all drivers have been converted.


Kind regards,
Niklas