On Friday 04 January 2013 05:51 PM, James Hogan wrote: > On 04/01/13 10:05, Vineet Gupta wrote: >> >> I have a kludge in ARC port in this subsystem - which I hope you could help clear. >> >> ARC also has a local timer device used for clockevent on each CPU. A one-time >> setup_irq() with IRQF_PERCPU - would indeed setup the generic IRQ subsystem - for >> making registration effective for all CPUs. However don't you need some per-cpu >> magic - say enabling the IRQ at cpu or embedded interrupt controller level - >> assuming you starts off with all IRQs disabled (which ARC Linux does). > Hi Vineet, > > For Meta this is done in secondary_start_kernel in > arch/metag/kernel/smp.c (see > https://github.com/jahogan/metag-linux/blob/metag-core/arch/metag/kernel/smp.c#L276). > It uses tbi_startup_interrupt which is also called by the irq_startup > callback for the root irq_chip. Aha, I see. Actually even that way is not bad - although doing that in local_timer_setup ( ) makes it much cleaner/obvious. So I can do the same and get rid of the obscure request/enable API and their dependency API - and it's workaround API .... which are used in only one more arch inexactly 1 place in the whole kernel. Another question if you don't mind. In our setup we have a UART (non-standard ARC specific) which is wired up to the boot CPU (only). Now if the init/rcS happens to run on non-boot CPU, the setup/request_irq( ) and hence consequential low level cpu irq unmasking will only happen on *that* cpu. Now if user were to type a key-stroke, the interrupt will be asserted on boot-cpu, which has interrupt masked. How is this handled. Many thx for your quick response. -Vineet -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
