Re: [Patch v7 4/7] PCI/ACPI: Add interface acpi_pci_root_create()

[Tomasz Nowicki]

On 21.10.2015 13:02, Liviu Dudau wrote:
> On Wed, Oct 21, 2015 at 11:57:53AM +0200, Tomasz Nowicki wrote:
> > On 14.10.2015 08:29, Jiang Liu wrote:
> > > Introduce common interface acpi_pci_root_create() and related data
> > > structures to create PCI root bus for ACPI PCI host bridges. It will
> > > be used to kill duplicated arch specific code for IA64 and x86. It may
> > > also help ARM64 in future.
> > >
> > > Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > > Tested-by: Tony Luck <tony.luck@xxxxxxxxx>
> > > Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Liu Jiang <jiang.liu@xxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/acpi/pci_root.c  |  204 ++++++++++++++++++++++++++++++++++++++++++++++
> > >   include/linux/pci-acpi.h |   24 ++++++
> > >   2 files changed, 228 insertions(+)
> >
> > [...]
> >
> > > +
> > > +struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> > > +				     struct acpi_pci_root_ops *ops,
> > > +				     struct acpi_pci_root_info *info,
> > > +				     void *sysdata)
> > > +{
> > > +	int ret, busnum = root->secondary.start;
> > > +	struct acpi_device *device = root->device;
> > > +	int node = acpi_get_node(device->handle);
> > > +	struct pci_bus *bus;
> > > +
> > > +	info->root = root;
> > > +	info->bridge = device;
> > > +	info->ops = ops;
> > > +	INIT_LIST_HEAD(&info->resources);
> > > +	snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
> > > +		 root->segment, busnum);
> > > +
> > > +	if (ops->init_info && ops->init_info(info))
> > > +		goto out_release_info;
> > > +	if (ops->prepare_resources)
> > > +		ret = ops->prepare_resources(info);
> > > +	else
> > > +		ret = acpi_pci_probe_root_resources(info);
> > > +	if (ret < 0)
> > > +		goto out_release_info;
> > > +
> > > +	pci_acpi_root_add_resources(info);
> > > +	pci_add_resource(&info->resources, &root->secondary);
> > > +	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
> > > +				  sysdata, &info->resources);
> >
> > Thank a lot for this cleanup!!
> >
> > I recall you already considered passing segment (domain nr) to
> > pci_create_root_bus, right? Can you please remind me why we gave up on this?
> >
> > I am asking because currently I can not find the way to retrieve domain
> > number from pci_bus_assign_domain_nr (for those platforms which choose
> > PCI_DOMAINS_GENERIC and want to use segment nr from MCFG table) which is the
> > part of pci_create_root_bus.
>
> Not sure I fully understand your question, but pci_bus_assign_domain_nr() will
> put the assigned domain number in bus->domain_nr if you chose PCI_DOMAINS_GENERIC.
> Do you want to override that value with the segment nr from MCFG?

Let me give ACPI ARM64 example:

1. We parse MCFG table and get segment nr assigned to root bridge
2. Then PCI host bridge calls acpi_pci_root_create -> 
pci_create_root_bus -> pci_bus_assign_domain_nr
3. At this point we cannot get segment nr for ACPI

So I would like to assign MCFG segment nr to bus->domain_nr being in 
pci_bus_assign_domain_nr giving we have scenario above.

Thanks,
Tomasz
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