Re: [PATCH V8 5/9] pci, acpi: add acpi hook to assign domain number.

Jon Masters
2016-06-10T18:55:49Z

Hi Bjorn,

Sorry for top posting while on the road. If this refactoring can happen later, is it possible to merge now (well, -next anyway) and explore other work as next steps?

Jon.

--
Computer Architect | Sent from my 64-bit #ARM Powered phone

> On Jun 10, 2016, at 13:18, Bjorn Helgaas <helgaas@kernel.org> wrote:
>
>> On Fri, Jun 10, 2016 at 06:49:32PM +0200, Tomasz Nowicki wrote:
>>> On 10.06.2016 17:49, Lorenzo Pieralisi wrote:
>>>> On Fri, Jun 10, 2016 at 04:14:58PM +0100, Lorenzo Pieralisi wrote:
>>>> Hi Bjorn, Tomasz,
>>>>
>>>> On Tue, Jun 07, 2016 at 07:15:59PM -0500, Bjorn Helgaas wrote:
>>>>
>>>> [...]
>>>>
>>>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>>>>>> index eb431b5..2b52178 100644
>>>>>> --- a/drivers/pci/pci.c
>>>>>> +++ b/drivers/pci/pci.c
>>>>>> @@ -7,6 +7,7 @@
>>>>>> * Copyright 1997 -- 2000 Martin Mares <mj@ucw.cz>
>>>>>> */
>>>>>>
>>>>>> +#include <linux/acpi.h>
>>>>>> #include <linux/kernel.h>
>>>>>> #include <linux/delay.h>
>>>>>> #include <linux/init.h>
>>>>>> @@ -4941,7 +4942,7 @@ int pci_get_new_domain_nr(void)
>>>>>> }
>>>>>>
>>>>>> #ifdef CONFIG_PCI_DOMAINS_GENERIC
>>>>>> -void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
>>>>>> +static int of_pci_bus_domain_nr(struct device *parent)
>>>>>
>>>>> Can we do a little cleanup before this patch?
>>>>>
>>>>> - pci_bus_assign_domain_nr() is only used inside drivers/pci, so
>>>>> maybe we move the prototype to drivers/pci/pci.h?
>>>>>
>>>>> - I don't really like the style of calling a function that
>>>>> internally assigns bus->domain_nr. Could we do something like
>>>>> this instead?
>>>>>
>>>>> int pci_bus_domain_nr(...)
>>>>> {
>>>>> ...
>>>>> return domain;
>>>>> }
>>>>>
>>>>> ... pci_create_root_bus(...)
>>>>> {
>>>>> ...
>>>>> b->domain_nr = pci_bus_domain_nr(...);
>>>>
>>>> We noticed while preparing v9, that this would force us to
>>>> write an empty pci_bus_domain_nr() prototype for
>>>> !PCI_DOMAINS_GENERIC (ie every arch but ARM/ARM64) that should
>>>> return 0 to keep current behaviour unchanged.
>>>>
>>>> That's why pci_bus_assign_domain_nr() was there, so that it
>>>> was compiled out on !PCI_DOMAINS_GENERIC.
>>>>
>>>> I really would like v9 to be final so let's fix it before posting it
>>>> shortly please.
>>>>
>>>> For the above we have three options:
>>>>
>>>> 1) Leave code as-is in v8
>>>>
>>>> 2) in pci_create_root_bus():
>>>> #ifdef CONFIG_PCI_DOMAINS_GENERIC
>>>> b->domain_nr = pci_bus_domain_nr(...);
>>>> #endif
>>>>
>>>> + other changes requested above
>>>>
>>>> 3) in pci_create_root_bus()
>>>>
>>>> b->domain_nr = pci_bus_domain_nr(...);
>>>>
>>>> unguarded and a stub:
>>>>
>>>> #ifndef CONFIG_PCI_DOMAINS_GENERIC
>>>> static inline int pci_bus_domain_nr() { return 0; }
>>>> #endif
>>>>
>>>> + other changes requested above
>>>
>>> Actually, Tomasz made me notice that pci_bus.domain_nr is
>>> only declared for CONFIG_PCI_DOMAINS_GENERIC so (3) is not
>>> even an option and IMO (2) is not much nicer than code in
>>> v8 as-is with an ifdef in the middle of pci_create_root_bus().
>>
>> To me (1) is nicer too. Bjorn what is your take on this? This is
>> last bit before sending v9.
>
> My preference is (2). The ifdef in pci_create_root_bus() is a little
> ugly, but I like it better because it will fit nicely into Arnd's
> idea of having the native drivers allocate and fill in a host bridge
> structure before calling the PCI core. The domain is one thing those
> drivers could fill in. I like that model much better than having the
> PCI core make callbacks to get information that we should have passed
> in to begin with.
>
> The current code suggests that assigning the domain is the PCI core's
> responsibility, and that's not really the case -- for ACPI it's
> totally up to pci_root.c, for other drivers it comes from the DT, and
> for others it might depend on the driver's knowledge of the hardware
> (I'm thinking of parisc, where, I think we currently put all the
> bridges in the same domain, but IIRC they *could* each be in their own
> domain with a full [bus 00-ff] range for each bridge because each
> bridge has its own config space access mechanism).
>
> But it's not that big a deal either way -- we could do this bit of
> restructuring later, too.
>
> Bjorn