Re: [PATCH V7 08/11] pci, acpi: Support for ACPI based generic PCI host controller

[Tomasz Nowicki <tn@semihalf.com>]

On 13.05.2016 13:31, Rafael J. Wysocki wrote:
> On Fri, May 13, 2016 at 1:25 PM, Jayachandran C <jchandra@broadcom.com> wrote:
>> On Tue, May 10, 2016 at 8:49 PM, Tomasz Nowicki <tn@semihalf.com> wrote:
>>> This patch is going to implement generic PCI host controller for
>>> ACPI world, similar to what pci-host-generic.c driver does for DT world.
>>>
>>> All such drivers, which we have seen so far, were implemented within
>>> arch/ directory since they had some arch assumptions (x86 and ia64).
>>> However, they all are doing similar thing, so it makes sense to find
>>> some common code and abstract it into the generic driver.
>>>
>>> In order to handle PCI config space regions properly, we define new
>>> MCFG interface which does sanity checks on MCFG table and keeps its
>>> root pointer. User is able to lookup MCFG regions based on that root
>>> pointer and specified domain:bus_start:bus_end touple. We are using
>>> pci_mmcfg_late_init old prototype to avoid another function name.
>>>
>>> The implementation of pci_acpi_scan_root() looks up the MCFG entries
>>> and sets up a new mapping (regions are not mapped until host controller ask
>>> for it). Generic PCI functions are used for accessing config space.
>>> Driver selects PCI_ECAM and uses functions from drivers/pci/ecam.h
>>> to create and access ECAM mappings.
>>>
>>> As mentioned in Kconfig help section, ACPI_PCI_HOST_GENERIC choice
>>> should be made on a per-architecture basis.
>>>
>>> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
>>> Signed-off-by: Jayachandran C <jchandra@broadcom.com>
>>> ---
>> [....]
>>
>>> diff --git a/drivers/pci/ecam.h b/drivers/pci/ecam.h
>>> index 1ad2176..1cccf57 100644
>>> --- a/drivers/pci/ecam.h
>>> +++ b/drivers/pci/ecam.h
>>> @@ -45,6 +45,11 @@ struct pci_config_window {
>>>                  void __iomem            *win;   /* 64-bit single mapping */
>>>                  void __iomem            **winp; /* 32-bit per bus mapping */
>>>          };
>>> +#ifdef CONFIG_ACPI_PCI_HOST_GENERIC
>>> +       struct acpi_device              *companion; /* ACPI companion device */
>>> +#endif
>>> +       int                             domain;
>>> +
>>>   };
>>
>> Using struct pci_config_window to pass along domain and
>> companion looks bad.  I think there are two possible options
>> to do this better:
>>
>> 1. add a 'struct fwnode_handle *' or 'struct device *parent_dev'
>>     instead of the companion and domain fields above. In case of
>>     ACPI either of them can be used to get the acpi_device and
>>     both  domain and companion can be set from that.
>>
>> 2. make pci_config_window fully embeddable by moving allocation
>>     out of pci_ecam_create to its callers. Then it can be embedded
>>     into acpi_pci_generic_root_info, and container_of can be used
>>     to get acpi info from ->sysdata.
>>
>> The first option should be easier to implement but the second may
>> be better on long run. I would leave it to the Bjorn or Rafael to
>> suggest which is preferred.
>
> Personally, I'd probably try to use fwnode_handle, but the second
> option makes sense too in principle.
>

Thanks for suggestions. I will try to use fwnode_handle

Tomasz