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

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Message-ID: <556EBE6D.90907@linaro.org>
Date:	Wed, 03 Jun 2015 16:44:29 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Jiang Liu <jiang.liu@...ux.intel.com>
CC:	"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年06月02日 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?

Thanks
Hanjun
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