Re: [RFC PATCH v2 11/21] PCI: MSI: Add helper function to set system wide MSI support

Thomas Gleixner
2023-10-30T19:29:53Z

On Mon, Oct 30 2023 at 23:24, Sunil V. L. wrote:
> On Mon, Oct 30, 2023 at 03:28:53PM +0100, Thomas Gleixner wrote:
> Just noting related discussion :
> https://www.spinics.net/lists/linux-serial/msg57616.html
>
> The MSI controller on RISC-V (IMSIC) is optional for the platform. So,
> when by default pci_msi_enable = 1 and the MSI controller is not
> discovered, we get stack trace like below.

<SNIP>

> So, what I did was, by default call pci_no_msi() to disable MSI and then
> call pci_set_msi() to enable when MSI controller is probed.

Your taste sensors should have gone out of range ...

> But I think Bjorn's suggestion to depend on PCI_BUS_FLAGS_NO_MSI may be
> better idea. In that case, we need to set bridge->msi_domain to true in
> pci_create_root_bus(). Let me know what do you prefer or if I am
> completely missing something here.

That's definitely more sensible, but as I said in the other thread, Marc
is the one who did the PCI core/bridge setup magic and he is definitely
in a better position to answer that bridge->msi_domain question.

Thanks,

tglx