Messages in this thread | | | Date | Wed, 29 Jul 2015 20:27:53 +0100 | From | Jon Hunter <> | Subject | Re: [PATCH] irqchip: gic: Add a cpu map for each GIC instance |
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On 29/07/15 19:33, Russell King - ARM Linux wrote: > On Wed, Jul 29, 2015 at 03:43:04PM +0100, Jon Hunter wrote: >> The gic_init_bases() function initialises an array that stores the mapping >> between the GIC and CPUs. This array is a global array that is >> unconditionally initialised on every call to gic_init_bases(). Although, >> it is not common for there to be more than one GIC instance, there are >> some devices that do support nested GIC controllers and gic_init_bases() >> can be called more than once. >> >> A 2nd call to gic_init_bases() will clear the previous CPU mapping and >> will only setup the mapping again for CPU0. This is because for child GIC >> controllers there is most likely only one recipient of the interrupt. >> >> Fix this by moving the CPU mapping array to the GIC chip data structure >> so that it is initialised for each GIC instance separately. It is assumed >> that the bL switcher code is only interested in the root or primary GIC >> instance. > > Does it make sense to expose the per-CPU-ness of the non-primary GIC? > If they are chained off a primary GIC SPI interrupt, then all IRQs on > the secondary GIC are routed to the same CPU that the SPI on the primary > GIC is routed to.
I am looking at a use-case where there is a secondary GIC and the secondary GIC is used as a interrupt router between the main CPU cluster and another CPU. So in this case the mapping of a secondary is still of interest. This patch does not address setting up the secondary mapping, but avoids a secondary GIC overwriting the primary map (which we don't want).
> Other features like the PPIs and SGIs in the secondary CPU should also > be ignored - they probably aren't used anyway.
Yes, agree.
> I have to say though... are the 1020 IRQs that the primary GIC provides > really not enough? What insane hardware needs more than 1020 IRQs?
Ha. I guess some realview boards for a start ...
# grep -r "gic_init(1" arch/arm/ arch/arm/mach-realview/realview_pb1176.c: gic_init(1, IRQ_PB1176_GIC_START, arch/arm/mach-realview/realview_eb.c: gic_init(1, 96, __io_address(REALVIEW_EB_GIC_DIST_BASE), arch/arm/mach-realview/realview_pb11mp.c: gic_init(1, IRQ_PB11MP_GIC_START,
Jon
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