Re: [PATCH v4 3/5] irqchip: Add DT binding doc for the virtual irq demuxer chip

[Mark Rutland]

On Tue, Feb 10, 2015 at 03:52:01PM +0000, Boris Brezillon wrote:
> Hi Mark,
> 
> On Tue, 10 Feb 2015 15:36:28 +0000
> Mark Rutland <mark.rutland@xxxxxxx> wrote:
> 
> > Hi Boris,
> > 
> > On Thu, Jan 29, 2015 at 10:33:38AM +0000, Boris Brezillon wrote:
> > > Add documentation for the virtual irq demuxer.
> > > 
> > > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
> > > Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
> > > ---
> > >  .../bindings/interrupt-controller/dumb-demux.txt   | 41 ++++++++++++++++++++++
> > >  1 file changed, 41 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt
> > > 
> > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt b/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt
> > > new file mode 100644
> > > index 0000000..b9a7830
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt
> > > @@ -0,0 +1,41 @@
> > > +* Virtual Interrupt Demultiplexer
> > > +
> > > +This virtual demultiplexer simply forward all incoming interrupts to its
> > > +enabled/unmasked children.
> > > +It is only intended to be used by hardware that do not provide a proper way
> > > +to demultiplex a source interrupt, and thus have to wake all their children
> > > +up so that they can possibly handle the interrupt (if needed).
> > > +This can be seen as an alternative to shared interrupts when at least one
> > > +of the interrupt children is a timer (and require the irq to stay enabled
> > > +on suspend) while others are not. This will prevent calling irq handlers of
> > > +non timer devices while they are suspended.
> > 
> > This sounds like a DT-workaround for a Linux implementation problem, and
> > I don't think this the right way to solve your problem.
> 
> I understand your concern, but why are you answering while I asked for
> DT maintainers reviews for several days (if not several weeks).
> 
> > 
> > Why does this have to be in DT at all? Why can we not fix the core to
> > handle these details?
> 
> We already discussed that with Rob and Thomas, and hiding such a
> demuxer chip is not an easy task.
> I'm open to any suggestion to do that, though I'd like you (I mean DT
> guys) to provide a working implementation (or at least a viable concept)
> that would silently demultiplex an irq.
> 
> > 
> > I am very much not keen on this binding.
> 
> Yes, but do you have anything else to propose.
> We're experiencing this warning for 2 releases now, and this is time to
> find a solution (even if it's not a perfect one).

Thoughts on the patch below?

Rather than handling this at the desc level it adds an extra flag to the
irqaction which can be set/unset during suspend for those irqs we don't
want to handle. That way we don't need to tell the core about the
mismatch explicitly in DT (or ACPI/board files/whatever).

If we can request/free interrupts during suspend then there's some logic
missing, but it shows the basic idea.

I didn't have a system to hand with shared mismatched IRQF_NO_SUSPEND
interrupts, so I had to fake that up in code for testing.

Thanks,
Mark.

---->8----