On Wed, Dec 09, 2015 at 03:31:41PM +0530, Jayachandran C. wrote:

[trimmed the cc list a bit]
On Mon, Dec 07, 2015 at 02:31:17PM -0600, Bjorn Helgaas wrote:

quoted

On Tue, Oct 27, 2015 at 05:38:31PM +0100, Tomasz Nowicki wrote:

[...]

quoted

quoted

Tomasz Nowicki (10):
  x86, pci: Reorder logic of pci_mmconfig_insert() function
  x86, pci, acpi: Move arch-agnostic MMCONFIG (aka ECAM) and ACPI code
    out of arch/x86/ directory
  pci, acpi, mcfg: Provide generic implementation of MCFG code
    initialization.
  x86, pci: mmconfig_{32,64}.c code refactoring - remove code
    duplication.
  x86, pci, ecam: mmconfig_64.c becomes default implementation for ECAM
    driver.
  pci, acpi, mcfg: Provide default RAW ACPI PCI config space accessors.
  pci, acpi, ecam: Add flag to indicate whether ECAM region was hot
    added or not.
  x86, pci: Use previously added ECAM hot_added flag to remove ECAM
    regions.

[...]

quoted

Waiting for an updated version after all the discussion.

Hi Bjorn,

After looking thru the code, I don't think moving the mmconfig code out
of x86 and using it in ARM64 is a good idea.

The code maintains a list of mapping of ECAM regions which can modified
at run time, and ends doing this sequence for doing a config access:

        rcu_read_lock();
        addr = pci_dev_base(seg, bus, devfn);
	        list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list)
			...find mapping...
	do pci operation
	rcu_read_unlock();

A lot of the complexity in mmconfig_*.c is to maintain and validate
the pci_mmcfg_list which seems to be unecessary.

That list is there to manage hotplug bridges, what makes you think
it is not necessary ? Jiang (in CC) can certainly comment on that and
how that list handling can be updated/simplified, if possible.

The better way would be to keep the mapping of ECAM region in the PCI
host bridge sysdata like pci-host-generic and directly access using
map_bus/read/write.

I see that early raw_pci_read/raw_pci_write may need to be supported.
I am not sure if this is needed in ARM64 - and if it is, we can handle
this by taking an early mapping for ECAM regions until the PCI host
bridges are setup, and dropping the mapping at that point.

I do not think it is needed (and if it is it can be added later, it
should not block this series), this was already debated in previous
threads (and in the ASWG, where basically nobody could provide a reason
why those raw accessors in ACPICA are meant to exist, they are there for
AML to access config space, why that has to be happen before PCI busses
are enumerated is still a mystery to me).

Lorenzo