linux-kernel - Re: [Patch v7 4/7] PCI/ACPI: Add interface acpi_pci_root

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Date:	Wed, 21 Oct 2015 19:49:13 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	Liviu Dudau <Liviu.Dudau@....com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Hanjun Guo <hanjun.guo@...aro.org>, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [Patch v7 4/7] PCI/ACPI: Add interface acpi_pci_root_create()

On 2015/10/21 19:27, 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@....com>
>>>> Tested-by: Tony Luck <tony.luck@...el.com>
>>>> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
>>>> Signed-off-by: Liu Jiang <jiang.liu@...ux.intel.com>
>>>> ---
>>>>   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.
Please use sysdata for that, IA64 and x86 are making use of sysdata
to store such information:
struct pci_sysdata {
        int             domain;         /* PCI domain */
        int             node;           /* NUMA node */
#ifdef CONFIG_ACPI
        struct acpi_device *companion;  /* ACPI companion device */
#endif
#ifdef CONFIG_X86_64
        void            *iommu;         /* IOMMU private data */
#endif
};

Hanjun once tried to introduce struct pci_sysdata for ARM64, but
seems it has been rejected.

> 
> Thanks,
> Tomasz
> -- 
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