> -----Original Message----- > From: Peter Maydell [mailto:[email protected]] > Sent: Monday, October 31, 2016 11:15 AM > To: Krzeminski, Marcin (Nokia - PL/Wroclaw) > <[email protected]> > Cc: QEMU Developers <[email protected]>; qemu-arm <qemu- > [email protected]>; [email protected] > Subject: Re: [v2] nvic: set pending status for not active interrupts > > On 31 October 2016 at 09:11, Krzeminski, Marcin (Nokia - PL/Wroclaw) > <[email protected]> wrote: > > Peter, > > > >> -----Original Message----- > >> From: Peter Maydell [mailto:[email protected]] > >> > +static void gic_set_irq_nvic(GICState *s, int irq, int level, > >> > + int cm, int target) { > >> > + if (level) { > >> > + GIC_SET_LEVEL(irq, cm); > >> > + if (GIC_TEST_EDGE_TRIGGER(irq) || GIC_TEST_ENABLED(irq, cm) > >> > + || !GIC_TEST_ACTIVE(irq, cm)) { > >> > + DPRINTF("Set %d pending mask %x\n", irq, target); > >> > + GIC_SET_PENDING(irq, target); > >> > + } > >> > >> Why is GIC_TEST_ENABLED() in this condition, when the idea is that we > >> don't care about the enabled status for whether we can pend the > interrupt? > >> > >> I think this should actually just always do > >> GIC_SET_PENDING(irq, target) > >> whenever level is high > >> > >> because: > >> (1) pending status can be set for disabled interrupts > >> (2) edge-triggered IRQs definitely always re-pend on rising edge > >> (3) I think level-triggered IRQs do too (it's a bit > >> less clear in the docs, but DUI0552A 4.2.9 says we pend on > >> a rising edge and doesn't say that applies only to edge > >> triggered IRQs) > >> > >> I don't have any real hardware to hand to test against, though. > >> > > Yes, it works exactly as you're saying (checked on HW), if level is > > still high after exit interrupt handler, interrupt is re-pend. > > "after exiting interrupt handler" is the wrong condition to check. > You need to: > * cause the interrupt line to be set > * enter the interrupt handler as a result (int becomes active) > * cause the interrupt line to be lowered (while in the handler) > * cause the interrupt line to be set again (still in the handler) > * check the interrupt pending state (still in the handler) > I performed this test, and when we are in interrupt handler (constantly pooling pending bit) interrupt is re-pend just after line is set again. V3 behaves in the same way.
Thanks, Marcin > If you only check the pending state after exiting the handler, then you can't > tell whether it was pended on the rising edge while active, or for the "re- > pend if high when we leave the interrupt handler". We know the hardware > does the latter, it's the former we're unsure about. > > thanks > -- PMM
