On Saturday, January 31, 2015 02:37:47 PM NeilBrown wrote: > On Sat, 31 Jan 2015 00:51:17 +0100 "Rafael J. Wysocki" <r...@rjwysocki.net> > wrote: > > > On Saturday, January 31, 2015 12:06:37 AM Rafael J. Wysocki wrote: > > > On Saturday, January 31, 2015 09:25:45 AM NeilBrown wrote: > > > > > > > > Nested IRQs can only fire when the parent irq fires. > > > > So when the parent is suspended, there is no need to suspend > > > > the child irq. > > > > > > > > Suspending nested irqs can cause a problem is they are suspended or > > > > resumed in the wrong order. > > > > If an interrupt fires while the parent is active but the child is > > > > suspended, then the interrupt will not be acknowledged properly > > > > and so an interrupt storm can result. > > > > This is particularly likely if the parent is resumed before > > > > the child, and the interrupt was raised during suspend. > > > > > > > > Ensuring correct ordering would be possible, but it is simpler > > > > to just never suspend nested interrupts. This patch does that. > > > > > > Clever. :-) > > > > > > This is fine by me. Thomas, what do you think? > > > > It looks like I've overlooked a potential problem, though. > > > > Can a nested interrupt be a wakeup one? We won't set IRQD_WAKEUP_ARMED for > > it > > then and may not handle wakeup correctly. > > > > I only have a fairly narrow understanding of this stuff, but if you have > nested interrupts, you would surely need the parent to be registered as a > wakeup interrupt, else the device wouldn't wake and the nested interrupt > would be ineffective until something else woke the device. > > Very few files mention both '.irq_set_wake' and 'irq_set_nested'. > > twl6040-irq.c has code to set irq_wake_enable on the parent if any nested > irqs have had irq_set_wake calls. > tps6586x.c has something similar, but much simpler. > arizona-irq.c and rc5t583-irq.c do the same as tps6586x.c > > So I think that any nested interrupts which might want to be wakeup > interrupts already deal with the issue, and I don't introduce a new problem > here.
Fair enough. I wonder if this means that it'll be useful to propagate IRQD_WAKEUP_STATE to parents, then ... Rafael
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