Subject: Re: [PATCH 4/7] powerpc/powernv: Patch MSI EOI handler on P8

From: Gavin Shan <[email-masked]>
Date: Thu, 25 Apr 2013 16:13:33 +0800

On Thu, Apr 25, 2013 at 04:08:37PM +0800, Gavin Shan wrote:
>On Thu, Apr 25, 2013 at 06:49:40AM +1000, Benjamin Herrenschmidt wrote:
>>On Wed, 2013-04-24 at 17:37 +0800, Gavin Shan wrote:
>>> The EOI handler of MSI/MSI-X interrupts for P8 (PHB3) need additional
>>> steps to handle the P/Q bits in IVE before EOIing the corresponding
>>> interrupt. The patch changes the EOI handler to cover that.
>>
>> .../...
>>

.../...

>>> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
>>> index a11b5a6..ea6a93d 100644
>>> --- a/arch/powerpc/platforms/powernv/pci.c
>>> +++ b/arch/powerpc/platforms/powernv/pci.c
>>> @@ -115,6 +115,25 @@ static void pnv_teardown_msi_irqs(struct pci_dev *pdev)
>>>  		irq_dispose_mapping(entry->irq);
>>>  	}
>>>  }
>>> +
>>> +int pnv_pci_msi_eoi(unsigned int hw_irq)
>>> +{
>>> +	struct pci_controller *hose, *tmp;
>>> +	struct pnv_phb *phb = NULL;
>>> +
>>> +	list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
>>> +		phb = hose->private_data;
>>> +		if (hw_irq >= phb->msi_base &&
>>> +		    hw_irq < phb->msi_base + phb->msi_bmp.irq_count) {
>>> +			if (!phb->msi_eoi)
>>> +				return -EEXIST;
>>> +			return phb->msi_eoi(phb, hw_irq);
>>> +		}
>>> +	}
>>> +
>>> +	/* For LSI interrupts, we needn't do it */
>>> +	return 0;
>>> +}
>>
>>And a list walk ... that's not right.
>>
>>Also, you do it for all XICS interrupts, including the non-PCI ones, the
>>LSIs, etc... only to figure out that some might not be MSIs later in
>>the loop.
>>
>>Why not instead look at changing the irq_chip for the MSIs ?
>>
>>IE. When setting up the MSIs for IODA2, use a different irq_chip which
>>is a copy of the original one with a different ->eoi callback, which
>>does the original xics eoi and then the OPAL stuff ?
>>
>>You might even be able to use something like container_of to get back
>>to the struct phb, no need to iterate them all.
>>
>
>Thanks for the detailed explaining, Ben.
>
>I found irq_data hasn't been fully utilized until this moment. I already
>have code to start use that. Firstly, "irq_data" is set to the PHB OPAL ID
>or invalid value (0xffs) during mapping stage (there, we call irq_set_chip_data()
>to trace the PHB OPAL ID or invalid value). Before EOIing the interrupt, we
>will check "irq_data" and do special handling on P/Q bits if it has valid value.
>With it, the "hot" path should be fast enough and the function pointer (mentioned
>above) can be removed.
>

It should be "chip_data" (not "irq_data"). Hopefully, you haven't
get time to see the reply. Otherwise, it would a bit confused ;-)

Thanks,
Gavin