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

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Message-ID: <5486C8BA.8030608@arm.com>
Date:	Tue, 09 Dec 2014 10:02:34 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Yijing Wang <wangyijing@...wei.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

Hi Yijing,

On 09/12/14 02:03, Yijing Wang wrote:
> On 2014/12/9 4:12, Marc Zyngier wrote:
>> In order to be able to populate the device msi_domain field,
>> add the necesary hooks to propagate the PHB msi_domain across
>> secondary busses to devices.
>>
>> So far, nobody populates the initial msi_domain.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>> ---
>>  drivers/pci/probe.c | 24 ++++++++++++++++++++++++
>>  include/linux/pci.h |  1 +
>>  2 files changed, 25 insertions(+)
>>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index c8ca98c..d1009a2 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -670,6 +670,20 @@ static void pci_set_bus_speed(struct pci_bus *bus)
>>  	}
>>  }
>>  
>> +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.

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?
- What topology data structures do you use to find out what MSI
controller a device should be matched with?
- What in-tree platform already has this requirements?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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