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SubjectRe: [PATCH] PCI: let pci_request_irq properly deal with threaded interrupts
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On 03.08.2018 21:40, Thomas Gleixner wrote:
> On Fri, 3 Aug 2018, Heiner Kallweit wrote:
>> On 03.08.2018 16:09, Thomas Gleixner wrote:
>>> On Wed, 1 Aug 2018, Heiner Kallweit wrote:
>>>> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
>>>> index 4ca2fd46..ba6da943 100644
>>>> --- a/kernel/irq/msi.c
>>>> +++ b/kernel/irq/msi.c
>>>> @@ -289,6 +289,9 @@ struct irq_domain *msi_create_irq_domain(struct fwnode_handle *fwnode,
>>>> if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
>>>> msi_domain_update_chip_ops(info);
>>>>
>>>> + /* MSI is oneshot-safe in general */
>>>> + info->chip->flags |= IRQCHIP_ONESHOT_SAFE;
>>>> +
>>>> domain = irq_domain_create_hierarchy(parent, IRQ_DOMAIN_FLAG_MSI, 0,
>>>
>>> Looks about right, though there might be dragons. MSI is not always as sane
>>> as it should be...
>>>
>> When saying "MSI isn't always sane", are you referring to the hardware or
>> the controller driver implementation? Basically for me the question is
>> whether we would be able to fix the issue if we meet such a dragon,
>> or whether we would have to revert the change.
>
> It's hardware unfortunately, so it might be a revert. PCI-MSI should be
> safe, but the wild MSI variants in SoCs might be the actual dragon caves.
>

pci_msi_create_irq_domain() is used by controller drivers for PCI(e)
controllers in SoCs like Mediatek, Armada, ..
I assume you're referring to some other (non-PCI) SoC-internal
MSI mechanism when saying "wild variants", right?

>> Do you think the chance of a dragon is low enough? Or better add the
>> flag only to the X86 PCI MSI irqchip for now?
>
> I think PCI-MSI in general would be not too risky. Famous last words.
>
> Thanks,
>
> tglx
>

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