Re: [Patch v7 4/7] PCI/ACPI: Add interface acpi_pci_root_create()
From: Tomasz Nowicki
Date: Wed Oct 21 2015 - 08:17:04 EST
On 21.10.2015 13:42, Lorenzo Pieralisi wrote:
On Wed, Oct 21, 2015 at 01:27:33PM +0200, Tomasz Nowicki wrote:
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.
I do not understand what you mean by "assign MCFG segment" here, please
explain. The MCFG segment group number is used to look-up the configuration
space for a given host bridge, not to assign a domain number to it.
The domain_nr above is the value returned by the _SEG object for the host
bridge device.
If I read the code correctly, MCFG region assigned to PCI host bridge X
should have the same value for its segment field and corresponding _SEG
object. Anyway, you are right, the MCFG segment group number should be
used to look-up the configuration space and _SEG object to retrieve
domain nr.
To evaluate _SEG object being in pci_bus_assign_domain_nr we still miss
there the PCI host bridge device. So I should change my previous
question, can we pass down the PCI host bridge device to be able to call
_SEG object being in pci_bus_assign_domain_nr?
Thanks,
Tomasz
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