linux-kernel - Re: [Patch v4 5/8] ARM64/PCI/ACPI: Introduce struct pci

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Message-ID: <556ED51C.4070302@linux.intel.com>
Date:	Wed, 03 Jun 2015 18:21:16 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Yijing Wang <wangyijing@...wei.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Lv Zheng <lv.zheng@...el.com>,
	"lenb @ kernel . org" <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"x86 @ kernel . org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [Patch v4 5/8] ARM64/PCI/ACPI: Introduce struct pci_controller
 for ACPI

On 2015/6/3 18:03, Lorenzo Pieralisi wrote:
> On Wed, Jun 03, 2015 at 10:36:19AM +0100, Jiang Liu wrote:
>> On 2015/6/3 16:44, Hanjun Guo wrote:
>>> On 2015???06???02??? 17:35, Lorenzo Pieralisi wrote:
>>>> On Tue, Jun 02, 2015 at 07:12:53AM +0100, Jiang Liu wrote:
>>>>> From: Hanjun Guo <hanjun.guo@...aro.org>
>>>>>
>>>>> ARM64 ACPI based PCI host bridge init needs a arch dependent
>>>>> struct pci_controller to accommodate common PCI host bridge
>>>>> code which is introduced later, or it will lead to compile
>>>>> errors on ARM64.
>>>>>
>>>>> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
>>>>> Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>>>>> CC: Arnd Bergmann <arnd@...db.de>
>>>>> CC: Catalin Marinas <catalin.marinas@....com>
>>>>> CC: Liviu Dudau <Liviu.Dudau@....com>
>>>>> CC: Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
>>>>> CC: Will Deacon <will.deacon@....com>
>>>>> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
>>>>> ---
>>>>>   arch/arm64/include/asm/pci.h |   10 ++++++++++
>>>>>   1 file changed, 10 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm64/include/asm/pci.h b/arch/arm64/include/asm/pci.h
>>>>> index b008a72f8bc0..70884957f253 100644
>>>>> --- a/arch/arm64/include/asm/pci.h
>>>>> +++ b/arch/arm64/include/asm/pci.h
>>>>> @@ -10,6 +10,16 @@
>>>>>   #include <asm-generic/pci-bridge.h>
>>>>>   #include <asm-generic/pci-dma-compat.h>
>>>>>
>>>>> +struct acpi_device;
>>>>> +
>>>>> +struct pci_controller {
>>>>> +#ifdef CONFIG_ACPI
>>>>> +    struct acpi_device *companion;    /* ACPI companion device */
>>>>> +#endif
>>>>> +    int        segment;    /* PCI domain */
>>>>> +    int        node;        /* NUMA node */
>>>>> +};
>>>>
>>>> There is nothing ARM64 specific in this structure. The only
>>>> reason I see you want to keep it arch specific is the iommu
>>>> pointer on x86,
>>>
>>> And also plarform_data for IA64 too.
>>>
>>>> but I think we should find a way to make
>>>> the common bits shared across archs (ie the struct above) and
>>>> add (maybe a void*) to the generic struct to cater for arch
>>>> specific data.
>>>>
>>>> Thoughts ?
>>>
>>> We discussed this already, it has limitations to make it
>>> common to all archs, I think the limitation are:
>>>
>>>   - struct pci_controller are also used for other archs
>>>     such as PowerPC and Tile, they will not use it for
>>>     ACPI purpose, so we can not used for all archs.
>>>
>>>   - if we let struct pci_controller defined only for archs
>>>     using ACPI, such as introduce it in linux/acpi.h, we still
>>>     can not satisfy that the struct pci_controller is not
>>>     only used for ACPI case on x86, it will be used for
>>>     non-ACPI too.
>>>
>>> So it's pretty difficult to share it with across archs to me,
>>> any more ideas?
>> Hi Hanjun and Lorenzo,
>> 	As mentioned by Hanjun, I have no idea yet about how to
>> consolidating "struct pci_controller" further. One possible
>> way is to move "struct pci_controller" related code into
>> arch, but apparently that will reduce code reusing.
> 
> I guess you can't move that struct pci_controller to generic code
> since it is present on other archs too (with completely different
> members).
> 
> What you can do is creating a new struct (ie same purpose of pci_controller
> with a different name) common to all archs that contains the common bits
> + a void* data that contains arch specific data, and convert x86 and ia64
> to using it.
> 
> It is weird to be forced to declare a pci_controller structure in arm64
> code with 0 arch specific data in it.

Hi Lorenzo,
	I have thought to consolidate pci_controller for x86 and ia64,
but that will make the change set much more bigger. How about to
consolidate pci_controller by another patch set. That will be easier
for review.
Thanks!
Gerry

> 
> Lorenzo
> 
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