Benjamin Herrenschmidt wrote: > On Wed, 2007-11-14 at 13:13 +1100, David Gibson wrote: >> Hrm. I *think* I'm convinced this is safe, although acking in a >> callback which doesn't say it acks is rather yucky. Essentially this >> code is trading flow readability (because just reading >> handle_level_irq will tell you something other than what it does in >> our case) for smaller code size. I'm not sure if this is a good trade >> or not. >>
It's not just code size. Actually, I was having problems with Ingo's real-time patch, that works on all platforms that use generic hard irq handlers and doesn't work just on 4xx since we use a custom one here. And I thought that using generic handlers would be easier to maintain. I agree that ack'ing in a callback which doesn't say it ack's looks odd, but ack'ing level-triggered interrupts is quirky on UIC itself. So, I just thought that adding a couple of quirks to mask_ack and unmask callbacks was not that bad. >> There's also one definite problem: according to the discussions I had >> with Thomas Gleixner when I wrote uic.c, handle_edge_irq is not what >> we want for edge interrupts. >> >> Apparently handle_edge_irq is only for edge interrupts on "broken" >> PICs which won't latch new interrupts while the irq is masked. UIC is >> not in this category, so handle_level_irq is actually what we want, >> even for an edge irq. >> >> Yes, I thought the naming was more than a little confusing, too. > > Hrm... handle_edge_irq works for both and you have a small performance > benefit in not masking, and thus using handle_edge_irq, so I don't > totally agree here. Basically, what handle_edge_irq() does is lazy > masking. Now there -is- an issue here is that if you do lazy masking, > you need to be able to re-emit in some convenient way. With the ack quirks added we can use handle_level_irq for edge-triggered interrupts. I'll test and resubmit the patch. > > Ben. > > Thanks, Valentine. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
