[PATCH v3 00/10] ARM: tegra: Add PCIe device tree support

[Bjorn Helgaas]

On Tue, Sep 18, 2012 at 12:33 AM, Thierry Reding
<thierry.reding at avionic-design.de> wrote:
> On Sat, Sep 08, 2012 at 11:51:00AM -0600, Bjorn Helgaas wrote:
>> On Fri, Sep 7, 2012 at 6:04 PM, Russell King - ARM Linux
>> <linux at arm.linux.org.uk> wrote:
>> > On Fri, Sep 07, 2012 at 05:34:35PM -0600, Stephen Warren wrote:
>> >> I guess it's a pretty basic premise of the current PCI code that all the
>> >> PCI scanning happens well before any device drivers are registered,
>> >> which in turn means that device_add() doesn't trigger the device's
>> >> probe() until much later, after all the fixups and resource assignments
>> >> are done?
>> >
>> > Are you saying that the PCI layer is again screwed up after all my
>> > hard work several years ago to ensure that PCI devices are properly
>> > setup _before_ they're made available to the PCI drivers then?  That
>> > was around the time I was looking at Cardbus stuff, ensuring that that
>> > worked with the same guarantees.
>> >
>> > Not amused.
>> >
>> > What is wrong with the "probe devices, apply fixups, setup resources,
>> > apply more fixups, publish" process that it's had to be yet again
>> > broken?
>>
>> It seems that there are some bugs in the PCI layer, no doubt
>> introduced after all your hard work.  We'll do our best to fix them.
>>
>> The particular issue of pci_fixup_irqs() has been on my list for a
>> while, and we talked about it at the recent PCI mini-summit.  It's
>> clearly broken that we do this with for_each_pci_dev() once at
>> boot-time because that does nothing for hot-added devices.  It's also
>> broken that it is called after device_add() because the core shouldn't
>> touch the device after it's available to drivers.
>>
>> This should get fixed reasonably soon, probably not in v3.6, but
>> hopefully in v3.7.  It's not completely trivial because many arches
>> have the same problem, and we need to fix all of them.
>
> Has there been any progress on this? I've read the PCI mini summit notes
> that you posted a while ago but it doesn't mention the pci_fixup_irqs()
> issue. Was there some decision as to how this should be solved? If I
> understand correctly this should solve the issue that Stephen has been
> seeing with bogus interrupt assignments, so we'll need this to fix PCIe
> on Tegra. Is there anything I can do to help move this forward?

I didn't mention pci_fixup_irqs() by name in the notes, but that's
part of what I meant by "device setup being done by initcalls" as a
hot-plug issue.  I know Myron Stowe expressed interest in working on
that, but I don't think he's had a chance to do anything yet (at
least, I haven't seen anything yet).

I don't have time to fix it myself, so moving it forward is just a
matter of somebody doing the work and posting the patches.  I think
that code just needs to be moved to some pcibios hook (possibly a new
one) that's called in the device_add path.

Bjorn