Hi Bjorn,
On 03.03.2016 23:51, Bjorn Helgaas wrote:
Hi Tomasz, Jayachandran, et al,
On Tue, Feb 16, 2016 at 02:53:31PM +0100, Tomasz Nowicki wrote:
From: Jayachandran C <jchandra@xxxxxxxxxxxx>
Move pci_mmcfg_list handling to a drivers/acpi/pci_mcfg.c. This is
to share the API and code with ARM64 later. The corresponding
declarations are moved from asm/pci_x86.h to linux/pci-acpi.h
As a part of this we introduce three functions that can be
implemented by the arch code: pci_mmconfig_map_resource() to map a
mcfg entry, pci_mmconfig_unmap_resource to do the corresponding
unmap and pci_mmconfig_enabled to see if the arch setup of
mcfg entries was successful. We also provide weak implementations
of these, which will be used from ARM64. On x86, we retain the
old logic by providing platform specific implementation.
This patch is purely rearranging code, it should not have any
impact on the logic of MCFG parsing or list handling.
I definitely want to figure out how to make this work well on ARM64.
I need to ponder this some more, so these are just some initial
thoughts.
My first impression is that (a) the x86 MCFG code is an unmitigated
disaster, and (b) we're trying a little too hard to make that mess
generic. I think we might be better served if we came up with some
cleaner, more generic code that we can use for ARM64 today, and
migrate x86 toward that over time.
My concern is that if we elevate the current x86 code to be
"arch-independent", we will be perpetuating some interfaces and
designs that shouldn't be allowed to escape arch/x86.
Some of the code that moved to drivers/acpi/pci_mcfg.c is not really
ACPI-specific, and could potentially be used for non-ACPI bridges that
support ECAM. I'd like to see that sort of code moved to a new file
like drivers/pci/ecam.c.
Actually I split it as you suggested in the previous patch set. Please
have a look at:
https://lkml.org/lkml/2016/2/4/646
Especially patches [0-6] which handle MMCONFIG refactoring.
Thanks,
Tomasz
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