On Tue, Feb 28, 2012 at 09:32:28PM +0100, Cousson, Benoit wrote: > Hi Russell, > > On 2/28/2012 3:36 PM, Russell King - ARM Linux wrote: >> On Tue, Feb 28, 2012 at 02:10:09PM +0100, Cousson, Benoit wrote: >>> The following commit: 2f31b51659c2d8315ea2888ba5b93076febe672b >>> Author: Tero Kristo<t-kristo@xxxxxx> >>> Date: Fri Dec 16 14:37:00 2011 -0700 >>> >>> ARM: OMAP4: PRM: use PRCM interrupt handler >>> >>> introduced the PRCM interrupt handler and thus the need >>> for 64 more interrupts. Since SPARSE_IRQ is still not fully >>> functional on OMAP, the NR_IRQS needs to be updated to avoid >>> the failure that happen during irq_alloc_descs call inside >>> the PRCM driver: >>> >>> [ 0.208221] PRCM: failed to allocate irq descs: -12 >>> >>> Later the mux framework is then unable to request an IRQ from >>> the PRCM interrupt handler. >>> >>> [ 1.802795] mux: Failed to setup hwmod io irq -22 >> >> This is fine for rc, but longer term... >> >> Do any of these have hard-coded interrupt numbers associated with them? >> If not, just enabling sparse IRQ will sort this out. > > You're right, in that case, it does not depend on any hard-coded number. > >> As I tried to explain yesterday, there are two modes for IRQ allocation: >> >> 1. Without sparse IRQ enabled, irq_alloc_descs(-1, from, num, -1) will >> allocate IRQs _within_ the existing from..NR_IRQS range, and will fail >> if there is insufficient IRQs available. >> >> 2. With sparse IRQs enabled, irq_alloc_descs(-1, from, num, -1) will >> allocate IRQs starting at max(from, NR_IRQS) and working upwards. >> >> In either case, irq_alloc_descs(start, 0, num, -1) will allocate 'num' >> IRQs at 'start' or fail if the range is already in use (and 0..NR_IRQS >> is defined as 'being in use' when sparse IRQs are enabled.) >> >> So, if the PRCM interrupts aren't statically assigned (the code suggests >> that they aren't) then it's already sparse-IRQ compliant, and enabling >> sparse IRQ support will mean that they will be allocated above NR_IRQS. >> >> Therefore, I suggest rather than raising NR_IRQS, you instead enable >> SPARSE_IRQ now so that anyone using the dynamic IRQ allocation can >> benefit from sparse IRQ support without having to have a large NR_IRQS. >> >> So, you don't have to wait until everything is converted to use >> sparse IRQ. You just need to make sure that nothing uses >> irq_alloc_descs(start, from, num, ...) where start< NR_IRQS, and >> nothing using that requires statically defined IRQ numbering. > > Yes, I fully agree, and that's still the plan. That's why I started > sending last week a bunch of cleanup for SPARSE_IRQ support. > Unfortunately, they might not be ready for 3.4 either, but I'm still > working on it. One thing I didn't consider is that the GIC has been converted to sparse IRQ support, so enabling it on OMAP will make the irq_alloc_descs() in there to fail if you try and keep it below NR_IRQS. That rules out a piecemeal conversion, which rather sucks. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
