Re: [v4] PCI: improve host drivers compile test coverage

[Rob Herring <robh@kernel.org>]

On Fri, Jun 15, 2018 at 11:55 AM, Scott Branden
<scott.branden@broadcom.com> wrote:
> Hi Lorenzo,
>
>
>
> On 18-06-15 05:58 AM, Lorenzo Pieralisi wrote:
>>
>> On Wed, Jun 13, 2018 at 11:11:46AM -0700, Guenter Roeck wrote:
>>>
>>> On Wed, Jun 13, 2018 at 11:09:35AM +0100, Lorenzo Pieralisi wrote:
>>>>
>>>> [+Jan, Ley Foon, RMK]
>>>>
>>>> On Tue, Jun 12, 2018 at 10:02:29AM -0700, Guenter Roeck wrote:
>>>>>
>>>>> On Thu, Apr 05, 2018 at 02:31:54PM -0500, Rob Herring wrote:
>>>>>>
>>>>>> Add COMPILE_TEST on driver config options with it. Some ARM drivers
>>>>>> still have arch dependencies, so we have to keep those dependent on
>>>>>> ARM.
>>>>>>
>>>>>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>>>>>> Cc: Bjorn Helgaas <bhelgaas@google.com>
>>>>>> Cc: linux-pci@vger.kernel.org
>>>>>> Signed-off-by: Rob Herring <robh@kernel.org>
>>>>>
>>>>> This patch has the undesirable side effect that it selects PCI_DOMAINS
>>>>> for
>>>>> sparc32:allmodconfig, which in turn results in
>>>>>
>>>>> drivers/ata/pata_ali.c: In function 'ali_init_chipset':
>>>>> drivers/ata/pata_ali.c:469:38: error:
>>>>>         implicit declaration of function 'pci_domain_nr'; did you mean
>>>>> 'pci_iomap_wc'?
>>>>>
>>>>> Unfortunately, 37bd62d224c82 ("PCI: Enable PCI_DOMAINS along with
>>>>> generic
>>>>> PCI host controller") has pretty much the same result. No idea how to
>>>>> fix
>>>>> the problem, so I won't even try.
>>>>
>>>> Sorry about that.
>>>>
>>>> One option would consist in removing all PCI_DOMAINS selection from
>>>> drivers/pci/controller/Kconfig and delegate it to arches even though
>>>> this would force PCI_DOMAINS selection on all ARM platforms (it is
>>>> already selected for ARCH_MULTIPLATFORM).
>>>>
>>>> Or we add back arch dependency to the relevant host bridges.
>>>>
>>>> Everything else I have in mind seems overkill to me given that this
>>>> patch was added to improve test coverage (we could add a default
>>>> pci_domain_nr() stub - weak or #define - that returns 0 in case arches
>>>> do not provide an implementation but do we really want to do that ?).
>>>>
>>>> Thoughts appreciated.
>>>>
>>>  From the definition of PCI_DOMAINS, I suspect the original idea was that
>>> drivers should depend on it, not select it. Especially auto-selecting
>>> it with PCI_HOST_GENERIC seems like a bad idea to me. However, that is
>>> just me. I'll leave it up to Bjorn to decide what if anything he wants
>>> to do about it.
>>
>> Here is a patch that should reinstate the previous behaviour but
>> it will make PCI_DOMAINS a visible option on ARM 32-bit systems; whether
>> that's acceptable that's the question I need to answer, it should
>> honour old configs and it does not force PCI_DOMAINS selection on
>> non-DT arch/arm PCI host controllers (that do not need PCI_DOMAINS
>> anyway so I suspect that enabling it on all ARM 32-bit platforms
>> should not break anything but I preferred to be cautious).
>
> I think this change will also require a patch enabling CONFIG_PCI_DOMAINS in
> multi_v7_defconfig and iproc_defconfig at the very least?

Perhaps the sub-arches that want this should select it. It is more a
platform option/decision more than a controller option.

Rob