[PATCH 0/2] arm64: acpi/pci: allow the firmware BAR configuration to be preserved

[Ard Biesheuvel]

On 6 June 2017 at 10:02, Lorenzo Pieralisi <lorenzo.pieralisi at arm.com> wrote:
> On Tue, Jun 06, 2017 at 09:14:26AM +0000, Ard Biesheuvel wrote:
>
> [...]
>
>> > Do you want me to create a branch out of these patches (inclusive of
>> > another patch to fix this bus reallocation policy discrepancy) for
>> > ARM64 folks to test ? Let me know, thanks !
>> >
>>
>> Hi Lorenzo,
>>
>> Bjorn has already picked up #1, which is now in -next. I will get back
>> to this topic today or tomorrow, so let me respin (including the bus
>> range fix) first, ok?
>
> Of course, I just want to help you make progress on this, I think
> we need help for testing them on ARM64 systems to see how to proceed.
>

OK, so I am hitting another issue. While it is quite simple to do this

"""
diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
index c7e3e6387a49..9a529c6369ac 100644
--- a/arch/arm64/kernel/pci.c
+++ b/arch/arm64/kernel/pci.c
@@ -203,6 +203,9 @@
                return NULL;
        }

+       /* ignore bus ranges assigned by the firmware */
+       pci_add_flags(PCI_REASSIGN_ALL_BUS);
+
        root_ops->release_info = pci_acpi_generic_release_info;
        root_ops->prepare_resources = pci_acpi_root_prepare_resources;
        root_ops->pci_ops = &ri->cfg->ops->pci_ops;
"""

and get the ACPI code to behave in the same way as the DT code,
including the resulting quirks, i.e.

pci_bus 0000:01: busn_res: can not insert [bus 01-ff] under [bus
00-0f] (conflicts with (null) [bus 00-0f])

there are two problems when we want to refine this to take _DSM #5 into account.

1) PCI_REASSIGN_ALL_BUS is a global flag, while _DSM is per PCI root
2) setting the flag conditionally on whether _DSM #5 allows it is
difficult to achieve, given that the flag needs to be set before
acpi_pci_root_create(), at which point we cannot access the _DSM yet

So I can send out the above as a separate patch, but right now, I am
not entirely sure how to proceed with conditionally preserving the
firmware configuration.