Re: [PATCH v4 03/10] of/irq: document properties for wakeup interrupt parent

[Lina Iyer]

On Mon, Mar 18 2019 at 11:54 -0600, Marc Zyngier wrote:
> On Wed, 13 Mar 2019 15:18:37 -0600
> Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote:
>
> Please do Cc Rob when posting DT related patches.
>
> > Some interrupt controllers in a SoC, are always powered on and have a
> > select interrupts routed to them, so that they can wakeup the SoC from
> > suspend. Add wakeup-parent DT property to refer to these interrupt
> > controllers.
> >
> > If the interrupts routed to the wakeup parent are not sequential, than a
> > map needs to exist to associate the same interrupt line on multiple
> > interrupt controllers. Providing this map in every driver is cumbersome.
> > Let's add this in the device tree and document the properties to map the
> > interrupt specifiers
> >
> > Signed-off-by: Lina Iyer <ilina@xxxxxxxxxxxxxx>
> > ---
> > Changes in v4:
> > 	- Added this documentation
> > ---
> >  .../interrupt-controller/interrupts.txt       | 39 +++++++++++++++++++
> >  1 file changed, 39 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt b/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> > index 8a3c40829899..917b598317f5 100644
> > --- a/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> > +++ b/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> > @@ -108,3 +108,42 @@ commonly used:
> >  			sensitivity = <7>;
> >  		};
> >  	};
> > +
> > +3) Interrupt wakeup parent
> > +--------------------------
> > +
> > +Some interrupt controllers in a SoC, are always powered on and have a select
> > +interrupts routed to them, so that they can wakeup the SoC from suspend. These
> > +interrupt controllers do not fall into the category of a parent interrupt
> > +controller and can be specified by the "wakeup-parent" property and contain a
> > +single phandle referring to the wakeup capable interrupt controller.
> > +
> > +   Example:
> > +	wakeup-parent = <&pdc_intc>;
> > +
> > +
> > +4) Interrupt mapping
> > +--------------------
> > +
> > +Sometimes interrupts may be detected by more than one interrupt controller
> > +(depending on which controller is active). The interrupt controllers may not
> > +be in hierarchy and therefore the interrupt controller driver is required to
> > +establish the relationship between the same interrupt at different interrupt
> > +controllers. If these interrupts are not sequential then a map needs to be
> > +specified to help identify these interrupts.
> > +
> > +Mapping the interrupt specifiers in the device tree can be done using the
> > +"irqdomain-map" property. The property contains interrupt specifier at the
> > +current interrupt controller followed by the interrupt specifier at the mapped
> > +interrupt controller.
> > +
> > +   irqdomain-map = <incoming-interrupt-specifier mapped-interrupt-specifier>
> > +
> > +The optional properties "irqdomain-map-mask" and "irqdomain-map-pass-thru" may
> > +be provided to help interpret the valid bits of the incoming and mapped
> > +interrupt specifiers respectively.
> > +
> > +   Example:
> > +	irqdomain-map = <22 0 &intc 36 0>, <24 0 &intc 37 0>;
> > +	irqdomain-map-mask = <0xff 0>;
> > +	irqdomain-map-pass-thru = <0 0xff>;
>
>
> This doesn't quite explain how the mask and pass-thru properties are
> used. I guess that the mask is used to define the 'useful bits' on the
> incoming side, but pass-thru puzzles me. In your example, does it mean
> that incoming lines map to outgoing interrupt <0 0>?
Sorry about the late reply.

How about this to go with the rest of the documentation -

In the above example, the input interrupt specifier map-mask <0xff 0> applied
on the incoming interrupt specifier of the map <22 0>, <24 0>, returns the
input interrupt 22, 24 etc. The second argument being irq type is immaterial
from the map and is used from the incoming request instead. The pass-thru
specifier parses the output interrupt specifier from the rest of the unparsed
argments from the map <&intc 36 0>, <&intc 37 0> etc to return the output
interrupt 36, 37 etc.


--Lina