Re: [PATCH V9 11/11] ARM64/PCI: Support for ACPI based PCI host controller

[Tomasz Nowicki <tn@semihalf.com>]

On 23.11.2016 19:22, Bjorn Helgaas wrote:
> On Wed, Nov 23, 2016 at 12:21:03PM +0100, Tomasz Nowicki wrote:
>> Hi Bjorn,
>>
>> On 23.11.2016 00:13, Bjorn Helgaas wrote:
>>> Hi Tomasz,
>>>
>>> On Fri, Jun 10, 2016 at 09:55:19PM +0200, Tomasz Nowicki wrote:
>>>> Implement pci_acpi_scan_root and other arch-specific call so that ARM64
>>>> can start using ACPI to setup and enumerate PCI buses.
>>>>
>>>> Prior to buses enumeration the pci_acpi_scan_root() implementation looks
>>>> for configuration space start address (obtained through ACPI _CBA method or
>>>> MCFG interface). If succeed, it uses ECAM library to create new mapping.
>>>> Then it attaches generic ECAM ops (pci_generic_ecam_ops) which are used
>>>> for accessing configuration space later on.
>>>> ...
>>>
>>>> +static struct acpi_pci_root_ops acpi_pci_root_ops = {
>>>> +	.release_info = pci_acpi_generic_release_info,
>>>> +};
>>>> +
>>>> +/* Interface called from ACPI code to setup PCI host controller */
>>>> struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
>>>> {
>>>> -	/* TODO: Should be revisited when implementing PCI on ACPI */
>>>> -	return NULL;
>>>> +	int node = acpi_get_node(root->device->handle);
>>>> +	struct acpi_pci_generic_root_info *ri;
>>>> +	struct pci_bus *bus, *child;
>>>> +
>>>> +	ri = kzalloc_node(sizeof(*ri), GFP_KERNEL, node);
>>>> +	if (!ri)
>>>> +		return NULL;
>>>> +
>>>> +	ri->cfg = pci_acpi_setup_ecam_mapping(root);
>>>> +	if (!ri->cfg) {
>>>> +		kfree(ri);
>>>> +		return NULL;
>>>> +	}
>>>> +
>>>> +	acpi_pci_root_ops.pci_ops = &ri->cfg->ops->pci_ops;
>>>
>>> This has already been merged, but this isn't right, is it?  We're
>>> writing a host controller-specific pointer into the single system-wide
>>> acpi_pci_root_ops, then passing it on to acpi_pci_root_create().
>>>
>>> Today, I think ri->cfg->ops->pci_ops is always &pci_generic_ecam_ops,
>> >from this path:
>>>
>>>  ri->cfg = pci_acpi_setup_ecam_mapping
>>>    cfg = pci_ecam_create(..., &pci_generic_ecam_ops)
>>>      cfg = kzalloc(...)
>>>      cfg->ops = ops             # &pci_generic_ecam_ops
>>>
>>> But we're about to merge the ECAM quirks series, which will mean it
>>> may not be &pci_generic_ecam_ops.  Even apart from the ECAM quirks, we
>>> should avoid this pattern of putting device-specific info in a single
>>> shared structure because it's too difficult to verify that it's
>>> correct.
>>>
>>
>> Well spotted. I agree, we need to fix this. How about this:
>> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
>> index fb439c7..31c0e1c 100644
>> --- a/arch/arm64/kernel/pci.c
>> +++ b/arch/arm64/kernel/pci.c
>> @@ -152,33 +152,35 @@ static void
>> pci_acpi_generic_release_info(struct acpi_pci_root_info *ci)
>>
>>         ri = container_of(ci, struct acpi_pci_generic_root_info, common);
>>         pci_ecam_free(ri->cfg);
>> +       kfree(ci->ops);
>>         kfree(ri);
>>  }
>>
>> -static struct acpi_pci_root_ops acpi_pci_root_ops = {
>> -       .release_info = pci_acpi_generic_release_info,
>> -};
>> -
>>  /* Interface called from ACPI code to setup PCI host controller */
>>  struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
>>  {
>>         int node = acpi_get_node(root->device->handle);
>>         struct acpi_pci_generic_root_info *ri;
>>         struct pci_bus *bus, *child;
>> +       struct acpi_pci_root_ops *root_ops;
>>
>>         ri = kzalloc_node(sizeof(*ri), GFP_KERNEL, node);
>>         if (!ri)
>>                 return NULL;
>>
>> +       root_ops = kzalloc_node(sizeof(*root_ops), GFP_KERNEL, node);
>> +       if (!root_ops)
>> +               return NULL;
>> +
>>         ri->cfg = pci_acpi_setup_ecam_mapping(root);
>>         if (!ri->cfg) {
>>                 kfree(ri);
>> +               kfree(root_ops);
>>                 return NULL;
>>         }
>>
>> -       acpi_pci_root_ops.pci_ops = &ri->cfg->ops->pci_ops;
>> -       bus = acpi_pci_root_create(root, &acpi_pci_root_ops, &ri->common,
>> -                                  ri->cfg);
>> +       root_ops->release_info = pci_acpi_generic_release_info;
>> +       root_ops->pci_ops = &ri->cfg->ops->pci_ops;
>> +       bus = acpi_pci_root_create(root, root_ops, &ri->common, ri->cfg);
>>         if (!bus)
>>                 return NULL;
>>
>> Of course, this should be the part of ECAM quirks core patches.
>>
>> The other option we have is to remove "struct pci_ops *pci_ops;"
>> from acpi_pci_root_ops structure and pass struct pci_ops as an extra
>> argument to acpi_pci_root_create(). What do you think?
>
> I think your patch above is fine and avoids the need to change the x86 and
> ia64 code.  Would you mind packaging this up with a changelog and
> signed-off-by?  I can take care of putting it in the ECAM series.
>

Sure, I have just sent the patch in replay to ECAM quirks V6 patch set.

Let us know when you update your branch so we base our quirks on it.

Thanks,
Tomasz