On Tuesday 26 March 2013, Thomas Petazzoni wrote: > > I've tried to explain that in the commit log of PATCH 6, which says: > > However, we need the driver to expose two different IRQ domains: one > for the main interrupt controller itself, and one for the MSI > interrupt controller. In order to achieve this, we will create two > subnodes in the interrupt-controller@d0020000 node: one subnode for > the main interrupt controller, and one subnode for the MSI interrupt > controller. The two irq domains can't be registered on the same DT > node, otherwise when irq_find_host() gets used by of_irq_map_one() > to resolve IRQs of devices, they may find the MSI interrupt > controller instead of the main interrupt controller. Right, I should have read the commit log better ... > Note that both the parent and the child node need to have the > 'interrupt-controller' empty property: > > * The interrupt-controller property is needed in the main > interrupt controller node (interrupt-controller@d0020000) because > the of_irq_init() function skips nodes that are matching the given > compatible string, but that don't have the interrupt-controller > property. > > * The interrupt-controller property is needed in the child > interrupt controller node (main-intc@d0020000) otherwise the > resolution done by of_irq_map_one() doesn't work. If you add compatible properties to the children, that would work I suppose. > So really, the thing is that irq_domain_add_linear() registers an IRQ > domain on a specific DT node, and then irq_find_host() finds back an > IRQ domain from a given DT node. So if you have two IRQ domains > registered on the same DT node, then you don't know which one will be > used. > > So if I do the two irq_domain_add_linear() (one for MPIC, one for MSI) > on one single DT node, when the timer driver will request its > interrupt, it turns out that the MSI IRQ domain is used and not the > MPIC IRQ domain, even though the timer has <&mpic> as its interrupt > parent. I still wonder if the real solution shouldn't instead be to make the irq domain code MSI aware. For instance, you don't really need a cell to describe an interrupt because the interrupt number is not a hardware property. So an MSI using device doesn't really needs an "msis" or "interrupts" property, just an "msi-parent", and we can add code to handle as a separate domain even if you have a single device node that can do both level and message interrupts. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
