Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges

[Jiang Liu <jiang.liu@huawei.com>]

On 2012-5-3 7:55, Bjorn Helgaas wrote:
> On Sun, Apr 8, 2012 at 11:12 AM, Jiang Liu<liuj97@gmail.com>  wrote:
>> This patch enhances pci_root driver to update MMCFG information when
>> hot-plugging PCI root bridges on x86 platforms.
>>
>> Signed-off-by: Jiang Liu<jiang.liu@huawei.com>
>> ---
>>   arch/x86/pci/acpi.c      |   58 ++++++++++++++++++++++++++++++++++++++++++++++
>>   drivers/acpi/pci_root.c  |   20 ++++++++++++++++
>>   include/acpi/acnames.h   |    1 +
>>   include/linux/pci-acpi.h |    3 ++
>>   4 files changed, 82 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
>> index da0149d..9184970 100644
>> --- a/arch/x86/pci/acpi.c
>> +++ b/arch/x86/pci/acpi.c
>> @@ -488,6 +488,64 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_pci_root *root)
>>         return bus;
>>   }
>>
>> +int arch_acpi_pci_root_add(struct acpi_pci_root *root)
>> +{
>> +       int result = 0;
>> +       acpi_status status;
>> +       unsigned long long base_addr;
>> +       struct pci_mmcfg_region *cfg;
>> +
>> +       /*
>> +        * Try to insert MMCFG information for host bridges with _CBA method
>> +        */
>> +       status = acpi_evaluate_integer(root->device->handle, METHOD_NAME__CBA,
>> +                                      NULL,&base_addr);
>
> I would prefer to have _CBA evaluated in drivers/acpi/pci_root.c, not
> in the arch code.  It's true that _CBA is probably only used by x86
> today, but the spec says nothing about it being arch-dependent, and I
> suspect it may be used on arm soon.
Good point. I just noticed that IA64 doesn't need MMCFG, but haven't
realized there's still another candidate.

>
>> +       if (ACPI_SUCCESS(status)) {
>> +               result = pci_mmconfig_insert(root->segment,
>> +                                            root->secondary.start,
>> +                                            root->secondary.end,
>> +                                            base_addr);
>> +               /*
>> +                * MMCFG information for hot-pluggable host bridges may have
>> +                * already been added by __pci_mmcfg_init();
>> +                */
>> +               if (result == -EEXIST)
>> +                       result = 0;
>> +       } else if (status == AE_NOT_FOUND) {
>> +               /*
>> +                * Check whether MMCFG information has been added for
>> +                * host bridges without _CBA method.
>> +                */
>> +               rcu_read_lock();
>> +               cfg = pci_mmconfig_lookup(root->segment, root->secondary.start);
>> +               if (!cfg || cfg->end_bus<  root->secondary.end)
>> +                       result = -ENODEV;
>> +               rcu_read_unlock();
>> +       } else
>> +               result = -ENODEV;
>> +
>> +       return result;
>> +}
>> +
>> +int arch_acpi_pci_root_remove(struct acpi_pci_root *root)
>> +{
>> +       acpi_status status;
>> +       unsigned long long base_addr;
>> +
>> +       /* Remove MMCFG information for host bridges with _CBA method */
>> +       status = acpi_evaluate_integer(root->device->handle, METHOD_NAME__CBA,
>> +                                      NULL,&base_addr);
>
> I think the arch-specific "map MMCONFIG space at this addr" should
> return a pointer or something that we can save and use to unmap it on
> remove.  That way we don't have to evaluate _CBA again.
OK, will change to follow that way.

>
>> +       if (ACPI_SUCCESS(status))
>> +               return pci_mmconfig_delete(root->segment,
>> +                                          root->secondary.start,
>> +                                          root->secondary.end,
>> +                                          base_addr);
>> +       else if (status != AE_NOT_FOUND)
>> +               return -ENODEV;
>> +
>> +       return 0;
>> +}
>> +
>>   int __init pci_acpi_init(void)
>>   {
>>         struct pci_dev *dev = NULL;
>> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
>> index 4a7d575..a62bfa8 100644
>> --- a/drivers/acpi/pci_root.c
>> +++ b/drivers/acpi/pci_root.c
>> @@ -448,6 +448,16 @@ out:
>>   }
>>   EXPORT_SYMBOL(acpi_pci_osc_control_set);
>>
>> +int __weak arch_acpi_pci_root_add(struct acpi_pci_root *root)
>> +{
>> +       return 0;
>> +}
>> +
>> +int __weak arch_acpi_pci_root_remove(struct acpi_pci_root *root)
>> +{
>> +       return 0;
>> +}
>> +
>>   static int __devinit acpi_pci_root_add(struct acpi_device *device)
>>   {
>>         unsigned long long segment, bus;
>> @@ -504,6 +514,14 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device)
>>         strcpy(acpi_device_class(device), ACPI_PCI_ROOT_CLASS);
>>         device->driver_data = root;
>>
>> +       if (arch_acpi_pci_root_add(root)) {
>> +               printk(KERN_ERR PREFIX
>> +                       "can't add MMCFG information for Bus %04x:%02x\n",
>> +                       root->segment, (unsigned int)root->secondary.start);
>> +               result = -ENODEV;
>> +               goto out_free;
>> +       }
>> +
>>         /*
>>          * All supported architectures that use ACPI have support for
>>          * PCI domains, so we indicate this in _OSC support capabilities.
>> @@ -629,6 +647,7 @@ out_del_root:
>>         list_del_rcu(&root->node);
>>         mutex_unlock(&acpi_pci_root_lock);
>>         synchronize_rcu();
>> +       arch_acpi_pci_root_remove(root);
>>   out_free:
>>         kfree(root);
>>         return result;
>> @@ -679,6 +698,7 @@ out:
>>         list_del_rcu(&root->node);
>>         mutex_unlock(&acpi_pci_root_lock);
>>         synchronize_rcu();
>> +       arch_acpi_pci_root_remove(root);
>>         kfree(root);
>>
>>         return 0;
>> diff --git a/include/acpi/acnames.h b/include/acpi/acnames.h
>> index 38f5088..99bda75 100644
>> --- a/include/acpi/acnames.h
>> +++ b/include/acpi/acnames.h
>> @@ -62,6 +62,7 @@
>>   #define METHOD_NAME__AEI        "_AEI"
>>   #define METHOD_NAME__PRW        "_PRW"
>>   #define METHOD_NAME__SRS        "_SRS"
>> +#define METHOD_NAME__CBA       "_CBA"
>>
>>   /* Method names - these methods must appear at the namespace root */
>>
>> diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
>> index ac93634..816b971 100644
>> --- a/include/linux/pci-acpi.h
>> +++ b/include/linux/pci-acpi.h
>> @@ -38,6 +38,9 @@ static inline acpi_handle acpi_pci_get_bridge_handle(struct pci_bus *pbus)
>>
>>   void acpi_pci_root_rescan(void);
>>
>> +extern int arch_acpi_pci_root_add(struct acpi_pci_root *root);
>> +extern int arch_acpi_pci_root_remove(struct acpi_pci_root *root);
>> +
>>   #else
>>
>>   static inline void acpi_pci_root_rescan(void) { }
>
> I don't know where to put this in the conversation, but I think we
> should separate the question of whether we do blind probing from the
> question of how we set up MMCONFIG space from MCFG.
>
> We currently parse the entire MCFG in some sort of initcall, but I
> think we *could* change the x86 blind probing routines to attempt to
> set up MMCONFIG space for the buses they find, just like
> acpi_pci_root_add() does it for the ACPI host bridges.
>
> That way we can continue blind probing, but make MMCONFIG init more sensible.
Good suggestion, will do more investigation about that.

>
> Bjorn
>
> .
>