Messages in this thread | | | Date | Fri, 24 Jan 2014 00:05:12 +0100 | From | Sebastian Hesselbarth <> | Subject | Re: [PATCH 3/3] irqchip: orion: clear stale interrupts in irq_enable |
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On 01/23/2014 11:52 PM, Jason Gunthorpe wrote: > On Thu, Jan 23, 2014 at 11:38:06PM +0100, Sebastian Hesselbarth wrote: >> Bridge IRQ_CAUSE bits are asserted regardless of the corresponding bit in >> IRQ_MASK register. To avoid interrupt events on stale irqs, we have to clear >> them before unmask. This installs an .irq_enable callback to ensure stale >> irqs are cleared before initial unmask. > > I'm not sure if putting this in irq_enable is correct. I think this > should only happen at irq_startup. > > The question boils down to what is supposed to happen with this code > sequence: > > disable_irq(..); > write(.. something to cause an interrupt edge ..); > .. synchronize .. > enable_irq(..); > > Do we get the interrupt or not?
Jason,
I get the point and actually I'd chosen .irq_enable because using .irq_startup didn't work. I rechecked this and now it works.. maybe it is getting too late for me. I'll send a v2 of this patch shortly.
Sebastian
> I found this message from Linus long ago: > http://yarchive.net/comp/linux/edge_triggered_interrupts.html >> Btw, the "disable_irq()/enable_irq()" subsystem has been written so that >> when you disable an edge-triggered interrupt, and the edge happens while >> the interrupt is disabled, we will re-play the interrupt at enable time. >> Exactly so that drivers can have an easier time and don't have to >> normally worry about whether something is edge or level-triggered. > > And found this note in Documentation/DocBook/genericirq.tmpl: > >> This prevents losing edge interrupts on hardware which does >> not store an edge interrupt event while the interrupt is disabled at >> the hardware level. > > So I think it is very clear that the chip driver should not discard > edges that happened while the interrupt was disabled. > > Regards, > Jason >
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