On 11/04/17 17:26, Mason wrote: > On 11/04/2017 17:49, Marc Zyngier wrote: >> On 11/04/17 16:13, Mason wrote: >>> On 27/03/2017 19:09, Marc Zyngier wrote: >>> >>>> Here's what your system looks like: >>>> >>>> PCI-EP -------> MSI Controller ------> INTC >>>> MSI IRQ >>>> >>>> A PCI MSI is always edge. No ifs, no buts. That's what it is, and nothing >>>> else. Now, your MSI controller signals its output using a level interrupt, >>>> since you need to whack it on the head so that it lowers its line. >>>> >>>> There is not a single trigger, because there is not a single interrupt. >>> >>> Hello Marc, >>> >>> I was hoping you or Thomas might help clear some confusion >>> in my mind around IRQ domains (struct irq_domain). >>> >>> I have read https://www.kernel.org/doc/Documentation/IRQ-domain.txt >>> >>> IIUC, there should be one IRQ domain per IRQ controller. >>> >>> I have this MSI controller handling 256 interrupts, so I should >>> have *one* domain for all possible MSIs. Yet the Altera driver >>> registers *two* domains (msi_domain and inner_domain). >>> >>> Could I make everything work with a single IRQ domain? >> >> No, because you have two irqchips. One that deals with the HW, and the >> other that deals with the MSIs how they are presented to the kernel, >> depending on the bus (PCI or something else). The fact that it doesn't >> really drive any HW doesn't make it irrelevant. > > The example given in IRQ-domain.txt is > > Device --> IOAPIC -> Interrupt remapping Controller -> Local APIC -> CPU > > with an irq_domain for each interrupt controller. Which doesn't use the generic MSI layer the way arm/arm64 do, so that's the wrong example. > > > On my system I have: > > PCI-EP -> MSI controller -> System INTC -> GIC -> CPU > > The driver for System INTC is drivers/irqchip/irq-tango.c > I think it has only one domain. > > For the GIC, drivers/irqchip/irq-gic.c > I see a call to irq_domain_create_linear() Can we please stick to the problem at hand and not drift into other considerations which do not matter at all? > Is the handling of MSI different, and that is why we need > two domains? (Sorry, I did not understand that part well.) Let me repeat it again, then: - You have a top-level MSI domain that is completely virtual, mapping a virtual hwirq to the virtual interrupt. Nothing to see here. - You have your own irqdomain, associated with your own irq_chip, which does what it needs to do talking to the HW and allocating interrupts. > When I looked at drivers/pci/host/pci-hyperv.c > they seem to have a single pci_msi_create_irq_domain call, > no call to domain_add or domain_create. > And they have a single struct irq_chip. Which is not using the generic MSI layer the way we do either. > >> You don't need to tell it anything about the number of interrupts you >> manage. As for your private structure, you've already given it to your >> low level domain, and there is no need to propagate it any further. > > My main issue is that in the ack callback, I was in the "wrong" > domain, in that d->hwirq was not the MSI number. So I thought > I needed a single irq_domain. No. You need two, but you only need to manage yours. > Is there a function to map virq to the hwirq in any domain? Be more precise. If you want the hwirq associated with the view of a virq in a given domain, that's the hwirq field in the corresponding irq_data structure. Or are you after something else? M. -- Jazz is not dead. It just smells funny...
