On Thu, 12 Sep 2013, Santosh Shilimkar wrote: > On Thursday 12 September 2013 08:26 PM, Thomas Gleixner wrote: > > Let me summarize: > > > > - GIC supports up to 160 interrupts > > > > - CROSSBAR supports up to 250 interrupts > > > > - CROSSBAR routes up to 160 out of 250 interrupts to the GIC ones > > > > - Drivers request a CROSSBAR interrupt number which must be mapped > > to some arbitrary available GIC irq number > > > Correct. > > > So basically the CROSSBAR mechanism is pretty much the same as MSI[X] > > just in a different flavour and with a different set of semantics and > > limitations, i.e. poor mans MSI[X] with a new level of bogosity. > > > > So if CROSSBAR is going to be the new fangled SoC MSI[X] long term > > equivalent then you better provide some infrastructure for that and > > make the drivers ready to use it. Maybe check with the PCI/MSI folks > > to share some of the interfaces. > > > > If that whole thing is another onetime HW designers wet dream, then > > please go back to the limited but completely functional (Who is going > > to use more than 160 peripheral interrupts????) device tree model. I > > really have no interest to support hardware designer brain farts. > > > Thanks for clear NAK for irqchip approach. I should have looped you > in the discussion where I was also suggesting against the irqchip > approach. We will try to look at MSI stuff but if its get too > complicated am going to fall-back to the initial probe based > approach to achieve the functionality. Before you dig into MSI, lets talk about irq domains first. GIC implements a legacy irq domain, i.e. a linear domain of all possible GIC interrupts with a 1:1 mapping. So why can't you make use of irq domains and have the whole routing business implemented sanely? What's needed is in gic_init_bases(): if (of_property_read(node, "routable_irqs", &nr_routable_irqs) { irq_domain_add_legacy(nr_gic_irqs); } else { irq_domain_add_legacy(nr_per_cpu_irqs); irq_domain_add_linear(nr_routable_irqs); } Now that separate domain has an xlate function which grabs a free GIC irq from a bitmap and returns the hardware irq number in the gic space. The map/unmap callbacks take care of setting up / tearing down the route in the crossbar. Thoughts? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html