Messages in this thread | | | From | Alexander Stein <> | Subject | Re: polarity inversion on LS1021a | Date | Mon, 04 Dec 2017 17:04:44 +0100 |
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On Monday, December 4, 2017, 4:37:20 PM CET Marc Zyngier wrote: > On 04/12/17 15:31, Alexander Stein wrote: > > On Monday, December 4, 2017, 4:11:06 PM CET Rasmus Villemoes wrote: > >> The LS1021A has a standard GIC-400, but allows inverting the polarity of > >> six external interrupt lines via a certain register, effectively > >> supporting IRQ_TYPE_LEVEL_LOW and IRQ_TYPE_EDGE_FALLING for those. > >> > >> I'm trying to figure out how one would add support for this. The patch > >> below works but is obviously just meant to help show what I mean, so > >> please don't comment on all the things that are wrong with it. > >> > >> It feels wrong to create a whole new irqchip driver copy-pasting the > >> entire irg-gic.c, but I can't figure out how and where one could hook > >> into the existing one. Any pointers on how to do this properly will be > >> greatly appreciated. > > > > In my opinion a new irqchip is still required, but solely for modifying > > SCFG_INTPCR depending on IRQ_TYPE_* > > You would need to insert it as a cascading interrupt chip in device tree. > > You also need to protect accesses to this register using a spinlock. > > This is at least my idea how I would have done it, though never got time > > for it. > Almost. See my earlier reply. You just need a very minimal driver that > only takes care of the polarity thing. Nobody needs to see yet another > GIC driver...
Ah, maybe I should have made that more clear. Of course only a rather simple driver for that single register is needed. The driver needs to handle the infamous big-little-endian mismatch in ls1021a.
Best regards, Alexander
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