On Wed, Jun 08, 2016 at 12:21:19PM +0200, Tomasz Nowicki wrote:

On 08.06.2016 02:15, Bjorn Helgaas wrote:

quoted

On Mon, May 30, 2016 at 05:14:18PM +0200, Tomasz Nowicki wrote:

quoted

PCI core code provides a config option (CONFIG_PCI_DOMAINS_GENERIC)
that allows assigning the PCI bus domain number generically by
relying on device tree bindings, and falling back to a simple counter
when the respective DT properties (ie "linux,pci-domain") are not
specified in the host bridge device tree node.

In a similar way, when a system is booted through ACPI, architectures
that are selecting CONFIG_PCI_DOMAINS_GENERIC (ie ARM64) require kernel
hooks to retrieve the domain number so that the PCI bus domain number
set-up can be handled seamlessly with DT and ACPI in generic core code
when CONFIG_PCI_DOMAINS_GENERIC is selected.

Since currently it is not possible to retrieve a pointer to the PCI
host bridge ACPI device backing the host bridge from core PCI code
(which would allow retrieving the domain number in an arch agnostic
way through the ACPI _SEG method), an arch specific ACPI hook has to
be declared and implemented by all arches that rely on
CONFIG_PCI_DOMAINS_GENERIC to retrieve the domain number and set it
up in core PCI code.

For the aforementioned reasons, this patch introduces a dummy
acpi_pci_bus_domain_nr() hook in preparation for per-arch implementation
of the same to retrieve the domain number on a per-arch basis when
the system boots through ACPI.

For the sake of code clarity the current code implementing generic
domain number assignment (ie pci_bus_assign_domain_nr(), selected by
CONFIG_PCI_DOMAINS_GENERIC) is reshuffled so that the code implementing
the DT domain assignment function is stubbed out into a corresponding
helper, so that DT and ACPI functions are clearly separated in
preparation for arches acpi_pci_bus_domain_nr() implementations.

Signed-off-by: Tomasz Nowicki <redacted>
Signed-off-by: Lorenzo Pieralisi <redacted>
---
 drivers/pci/pci.c   | 11 +++++++++--
 include/linux/pci.h |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index eb431b5..2b52178 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c

@@ -7,6 +7,7 @@
  *	Copyright 1997 -- 2000 Martin Mares <mj@ucw.cz>
  */

+#include <linux/acpi.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/init.h>

@@ -4941,7 +4942,7 @@ int pci_get_new_domain_nr(void)
 }

 #ifdef CONFIG_PCI_DOMAINS_GENERIC
-void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
+static int of_pci_bus_domain_nr(struct device *parent)

Can we do a little cleanup before this patch?

  - pci_bus_assign_domain_nr() is only used inside drivers/pci, so
    maybe we move the prototype to drivers/pci/pci.h?

pci_bus_assign_domain_nr() goes with pci_domain_nr() as an option
for CONFIG_PCI_DOMAINS_GENERIC. pci_domain_nr() is used commonly
outside drivers/pci so we would need to split these calls then, thus
personally I think it would be better to keep both in
inclue/linux/pci.h

OK.

quoted

  - I don't really like the style of calling a function that
    internally assigns bus->domain_nr.  Could we do something like
    this instead?

    int pci_bus_domain_nr(...)
    {
      ...
      return domain;
    }

    ... pci_create_root_bus(...)
    {
      ...
      b->domain_nr = pci_bus_domain_nr(...);

We can. I do not see much difference between pci_bus_domain_nr() and
pci_domain_nr() which we already have so how about calling it
pci_bus_find_domain_nr instead? Lorenzo, any strong preference for
it?

I suggested that to make them all parallel:

  pci_bus_domain_nr()
  of_pci_bus_domain_nr()
  acpi_pci_bus_domain_nr()

If you want to make them all *pci_bus_find_domain_nr() that would be
OK with me, but I think it is worth keeping them the same except for
the prefix (none/"of_"/"acpi_").  I think that's what you suggested
below.

quoted

That would be two new patches, if this makes sense.

And this patch would only rename pci_bus_assign_domain_nr() to
of_pci_bus_domain_nr() and add the pci_bus_domain_nr() wrapper.

Giving that we would keep prototypes in inclue/linux/pci.h

1. First patch would rename pci_bus_assign_domain_nr() to
pci_bus_find_domain_nr() and it would return domain number so that
we could do:
     ... pci_create_root_bus(...)
     {
       ...
       b->domain_nr = pci_bus_domain_nr(...);
       ...
     }

2. Second patch would transform pci_bus_find_domain_nr() to be the
wrapper for of_pci_bus_domain_nr()

3. Third patch would add stub definition, the ARM64 definition and
the new call acpi_pci_bus_domain_nr() in pci_bus_find_domain_nr()
wrapper.

Does this plan sound reasonable?

Sounds perfect!