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From: Jan Kiszka <jan.kiszka@siemens.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Rob Herring <robh@kernel.org>,
	Scott Branden <scott.branden@broadcom.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, Ley Foon Tan <lftan@altera.com>,
	Russell King <linux@armlinux.org.uk>
Subject: Re: [v4] PCI: improve host drivers compile test coverage
Date: Mon, 18 Jun 2018 18:53:10 +0200	[thread overview]
Message-ID: <03d3eac6-4711-2bd5-4ab5-fc2f77d5e4ad@siemens.com> (raw)
In-Reply-To: <20180618125255.GA356@red-moon>

On 2018-06-18 14:52, Lorenzo Pieralisi wrote:
> On Mon, Jun 18, 2018 at 01:42:25PM +0200, Jan Kiszka wrote:
>> On 2018-06-18 11:32, Lorenzo Pieralisi wrote:
>>> On Fri, Jun 15, 2018 at 12:34:51PM -0600, Rob Herring wrote:
>>>> 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.
>>>
>>> Yes, that makes sense, I assume ARCH_VIRT is a sensible choice for
>>> virtual machines configuration, Jan ?
>>>
>>> I will add a PCI_DOMAINS selection to all (ARM) arches that select
>>> PCI_DOMAINS in drivers/pci/controller/Kconfig.
>>>
>>> For Jailhouse configurations I need Jan's input, I assume adding
>>> the selection to ARCH_VIRT is the correct way forward, please let
>>> me know asap.
>>
>> So far, there is no need on ARM or ARM64 declare a special platform in
>> order to run as Jailhouse (secondary) guest.
>>
>> My original patch was just about making PCI_DOMAINS manually
>> configurable, which would have been fine for our use case.
> 
> I need more details on your system configuration to make sure we can fix
> this in a way that does not upset anybody; I am not a big fan of making
> PCI_DOMAINS visible since it affects other platforms and it is different
> from how it is managed for all other arches, so please provide details.

Our setup is as follows: A platform, e.g. Jetson TK1 or TX1/2, already
has one PCI host controller. When enabling Jailhouse on it (from within
a running Linux), this adds the generic PCI host controller as virtual
one. So we need to configure the system to support both controllers and
PCI domains. But, otherwise, the system does not look different from a
physical one.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

  reply	other threads:[~2018-06-18 16:53 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-05 19:31 [PATCH v4] " Rob Herring
2018-05-18 21:42 ` Bjorn Helgaas
2018-05-19 19:22   ` Rob Herring
2018-06-12 17:02 ` [v4] " Guenter Roeck
2018-06-13 10:09   ` Lorenzo Pieralisi
2018-06-13 18:11     ` Guenter Roeck
2018-06-14 16:53       ` Lorenzo Pieralisi
2018-06-15 12:58       ` Lorenzo Pieralisi
2018-06-15 17:55         ` Scott Branden
2018-06-15 17:58           ` Scott Branden
2018-06-18 11:34             ` Lorenzo Pieralisi
2018-06-15 18:34           ` Rob Herring
2018-06-18  9:32             ` Lorenzo Pieralisi
2018-06-18 11:42               ` Jan Kiszka
2018-06-18 12:52                 ` Lorenzo Pieralisi
2018-06-18 16:53                   ` Jan Kiszka [this message]
2018-06-19  9:27                     ` Lorenzo Pieralisi

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