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

[Thierry Reding <thierry.reding@avionic-design.de>]

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On Tue, Aug 14, 2012 at 01:39:23PM -0600, Stephen Warren wrote:
> On 08/13/2012 05:18 PM, Bjorn Helgaas wrote:
> > On Mon, Aug 13, 2012 at 11:47 AM, Stephen Warren <swarren@wwwdotorg.org> wrote:
> ...
> >> whereas for a device tree boot:
> >>
> >> (same):
> >>> [    2.112217] pci 0000:01:00.0: reg 10: [io  0x0000-0x00ff]
> >>> [    2.117635] pci 0000:01:00.0: reg 18: [mem 0x00000000-0x00000fff 64bit pref]
> >>> [    2.124690] pci 0000:01:00.0: reg 20: [mem 0x00000000-0x00003fff 64bit pref]
> >>> [    2.131731] pci 0000:01:00.0: reg 30: [mem 0x00000000-0x0001ffff pref]
> >> ... (request region happens early)
> >>> [    2.179838] r8169 0000:01:00.0: BAR 0: requesting [io  0x0000-0x00ff]
> >>> [    2.193312] r8169 0000:01:00.0: BAR 2: requesting [mem 0x00000000-0x00000fff 64bit pref]
> >>> [    2.201397] r8169 0000:01:00.0: BAR 2: can't reserve [mem 0x00000000-0x00000fff 64bit pref]
> >>> [    2.209742] r8169 0000:01:00.0: (unregistered net_device): could not request regions
> >> ... (same, just happens too late)
> >>> [    2.236818] pci 0000:01:00.0: BAR 6: assigned [mem 0xa0000000-0xa001ffff pref]
> >>> [    2.244027] pci 0000:01:00.0: BAR 4: assigned [mem 0xa0020000-0xa0023fff 64bit pref]
> >>> [    2.251794] pci 0000:01:00.0: BAR 2: assigned [mem 0xa0024000-0xa0024fff 64bit pref]
> >>> [    2.259542] pci 0000:01:00.0: BAR 0: assigned [io  0x1000-0x10ff]
> >>
> >> I suspect this is all still related to the PCI devices themselves being
> >> probed much earlier in the overall PCI initialization sequence when the
> >> PCI controller is probed later in the boot sequence, whereas PCI device
> >> probe is deferred until the overall PCI initialization sequence is
> >> complete if the PCI controller is probed very early in the boot sequence.
> > 
> > I don't know what to apply your patches to (they don't apply cleanly
> > to v3.6-rc2), so I can't see exactly what you're doing.  But it looks
> > like you might be calling pci_bus_add_devices() before
> > pci_bus_assign_resource(), which isn't going to work.
> 
> Yes, that's exactly what is happening.
> 
> PCIe initialization starts in arch/arm/mach-tegra/pci.e
> tegra_pcie_init() which calls arch/arm/kernel/bios32.c
> pci_common_init(). That function first calls pcibios_init_hw() (in the
> same file, more about this later) and then loops over PCI buses, calling
> amongst other things pci_bus_assign_resources() then pci_bus_add_devices().
> 
> The problem is that ARM's pcibios_init_hw() calls pci_scan_root_bus()
> (or a host-driver-specific function which that also calls
> pci_scan_root_bus() in Tegra's case) which in turn calls
> pci_bus_add_devices() right at the end, before control has returned to
> pci_common_init() and hence before pci_bus_assign_resources() has been
> called.
> 
> If I modify pci_scan_root_bus() and remove the call to
> pci_bus_add_devices(), everything works as expected.
> 
> So, I guess the question is: Should ARM's pcibios_init_hw() not be
> calling pci_scan_root_bus(), or at least presumably the ARM PCI code
> needs to do things in a slightly different order?

Maybe pci_scan_root_bus() should be calling pci_bus_assign_resources()?
Or a new function could be added which also assigns the resources.

Thierry

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