Subject: Re: [PATCH v2 2/2] powerpc/PCI: Disable MSI/MSI-X interrupts at PCI probe time in OF case

From: "Guilherme G. Piccoli" <[email-masked]>
Date: Fri, 4 Sep 2015 20:17:12 -0300

Hello Bjorn,

> of_create_pci_dev() already has a lot of code that duplicates
> pci_setup_device(), and it's a shame to add more.  There's also a sparc
> version of of_create_pci_dev() that presumably has the same problem you're
> fixing for powerpc.

Thanks for the information!

> Michael originally called pci_msi_setup_pci_dev() from
> pci_init_capabilities() [1].  A subsequent patch moved the call
> to pci_setup_device() [2] because an early quirk (called from
> pci_setup_device()) used pci_msi_off(), which depended on
> pci_msi_setup_pci_dev().
>
> But we later removed pci_msi_off() completely, so I think we probably
> *could* call pci_msi_setup_pci_dev() from pci_init_capabilities().
>
> That would be much nicer because it makes more sense there, and it
> would do the right thing for powerpc and sparc because they both
> already use that path.
>
> Can you look into moving the call?

I might have misunderstood something here (sorry if it's the case), but 
moving the call to pci_init_capabilities() has the same practical 
implications than reverting my 2 commmits [1] [2] and Michael Tsirkin's 
commit [3], except when CONFIG_PCI_MSI is not set - in this case, moving 
the call would initialize MSI capabilities anyway, since 
pci_init_capabilities() executes even if CONFIG_PCI_MSI isn't set.

My question is: is necessary to initialize MSI capabilities even with 
CONFIG_PCI_MSI not set? In negative case, would be "cleaner" revert the 
3 commits, right?

On the other hand, if it's necessary to initialize MSI capabilities on 
devices anyway, we can change the call place.

Let me know your opinion, and I'm sorry if I misunderstood something here.

Cheers,

Guilherme Piccoli

[1] commit 22b6839b914b ("PCI: Make pci_msi_setup_pci_dev() non-static 
for use by arch code")

[2] commit 4d9aac397a5d ("powerpc/PCI: Disable MSI/MSI-X interrupts at 
PCI probe time in OF case")

[3] commit 1851617cd2da ("PCI/MSI: Disable MSI at enumeration even if 
kernel doesn't support MSI")