linux-kernel - Re: [PATCH 2/6] PCI/MSI: add hooks to populate the msi

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Date:	Tue, 9 Dec 2014 20:24:32 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Marc Zyngier <marc.zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>
Subject: Re: [PATCH 2/6] PCI/MSI: add hooks to populate the msi_domain field

>>> Well, this is not supposed to be a perfect solution yet, but instead a
>>> basis for discussion. What I'd like to find out is:
>>>
>>> - What is the minimum granularity for associating a device with its MSI
>>> domain in existing platforms?
>>
>> PCI device, after Gerry's msi irq domain patchset which now in linux-next,
>> in x86, we will find msi irq domain by pci_dev.
> 
> Are you *really* associating the MSI domain on a per pci-device basis?
> That is, you have devices on the same PCI bus talking to different MSI hw?

Yes.

> 
>> I generally agree your first patch which associate basic device with msi irq domain.
>>
>>> - What topology data structures do you use to find out what MSI
>>> controller a device should be matched with?
>>
>> Now only arm and arm64 use msi controller to setup/teardown msi irqs,
>> in arm, now msi controller saved in pci_sys_data, and for arm64, it seems
>> to be saved in pci_bus. For a more common method to find msi controller/irq domain,
>> I prefer pci_dev/device.
> 
> Forget about msi_controller, the whole goal of this series is to make it
> obsolete. On your x86 platform, what how do you identify which MSI
> domain should be associated with a given PCI device? Surely you must
> have a set of data structures or ACPI tables which give you that
> information.

Yes, by ACPI DMAR table.

> 
>>> - What in-tree platform already has this requirements?
>>
>> As mentioned above, x86 does.
> 
> Let me rephrase that in a non-ambiguous manner: can you point me to a
> file implementing this in mainline?

Please refer to arch/x86/kernel/apic/msi.c  native_setup_msi_irqs()  in linux-next tree.

Thanks!
Yijing.

> 
> Thanks,
> 
> 	M.
> 


-- 
Thanks!
Yijing

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