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

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Date:	Tue, 9 Dec 2014 19:57:51 +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

>>> +void __weak pcibios_set_phb_msi_domain(struct pci_bus *bus)
>>> +{
>>> +}
>>> +
>>> +static void pci_set_bus_msi_domain(struct pci_bus *bus)
>>> +{
>>> +	struct pci_dev *bridge = bus->self;
>>> +
>>> +	if (!bridge)
>>> +		pcibios_set_phb_msi_domain(bus);
>>> +	else
>>> +		dev_set_msi_domain(&bus->dev, dev_get_msi_domain(&bridge->dev));
>>> +}
>>
>>
>> Hi Marc, we can not assume pci devices under same phb share the same msi irq domain,
>> now in x86, pci devices under the same phb may associate different msi irq domain.

Hi Marc,

> 
> 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.

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.

> - What in-tree platform already has this requirements?

As mentioned above, x86 does.


Thanks!
Yijing.




> 
> Thanks,
> 
> 	M.
> 


-- 
Thanks!
Yijing

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