On Wed, Feb 29, 2012 at 08:35:27PM +0000, Jonathan Cameron wrote: > On 02/29/2012 02:32 PM, Maxime Ripard wrote: > > Hi everyone, > > > > I'm working on adding the support for the AT91SAM9M10G45-EK board from > > Atmel for the at91_adc driver I previously posted, and I encounter some > > weird issue here. > > > > When calling the iio_allocate_trigger > > (http://lxr.free-electrons.com/source/drivers/staging/iio/industrialio-trigger.c?a=arm#L421) > > from my driver on the G45, it returns ENOMEM, while on the > > AT91SAM9G20-EK board, it works perfectly. > > > > Digging a bit into it, it seems that the call to irq_alloc_descs is > > returning the error (the value of CONFIG_IIO_CONSUMERS_PER_TRIGGER is 2 > > in my configuration, which seems pretty reasonable and is the default > > value anyway), which is itself getting that return value from > > irq_expand_nr_irqs. > > > > Here, I'm left confused, I don't know this part of the kernel anymore, > > and most importantly, it seems to be pretty-much arch-independant, while > > the nature of my issue seems really platform-dependant. > > > > Do you have any clue of what's going on here ? > We ran into this originally on the pxa as well. My guess is that > nr_irqs is not set high enough for that particular board. > > Looking back I can find some mention of a nasty bit of code that > just adds a bit of padding but I can't find it now. > > Anyhow, you probably have a line somewhere in the kernel log > saying something like: > > [ 0.000000] NR_IRQS:288 nr_irqs:296 296 > > NR_IRQS is typically the number of the SoC > nr_irqs should be large enough to accomodate those provided by > other peripherals. > > I also have a vague recollection that the problem goes away entirely > with sparse irqs? Yes, because IRQs will be allocated above the last figure on that line, up to IRQ_BITMAP_BITS which happens to be 8192 above NR_IRQS. There's an issue though: if your on-SoC IRQ controller is already using irq_alloc_descs(), it will fail if you want it to grab IRQs below the last figure on that line, because those will have already been allocated for you. -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
