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. 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() Is the handling of MSI different, and that is why we need two domains? (Sorry, I did not understand that part well.) 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. > 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. Is there a function to map virq to the hwirq in any domain? Regards.
