Re: [PATCH 1/2] dt-bindings: irqchip: Introduce TISCI Interrupt router bindings

[Rob Herring <robh@kernel.org>]

On Sat, Oct 06, 2018 at 11:29:29AM -0500, Nishanth Menon wrote:
> On 12:58-20181006, Lokesh Vutla wrote:
> > Add the DT binding documentation for Interrupt router driver.
> > 
> > Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
> > ---
> >  .../interrupt-controller/ti,sci-intr.txt      | 83 +++++++++++++++++++
> >  MAINTAINERS                                   |  1 +
> >  2 files changed, 84 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt b/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> > new file mode 100644
> > index 000000000000..681ca53cc5fb
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> > @@ -0,0 +1,83 @@
> > +Texas Instruments K3 Interrupt Router
> > +=====================================
> > +
> > +The Interrupt Router (INTR) module provides a mechanism to mux M
> > +interrupt inputs to N interrupt outputs, where all M inputs are selectable
> > +to be driven per N output. There is one register per output (MUXCNTL_N) that
> > +controls the selection.
> > +
> > +
> > +                                 Interrupt Router
> > +                             +----------------------+
> > +                             |  Inputs     Outputs  |
> > +        +-------+            | +------+             |
> > +        | GPIO  |----------->| | irq0 |             |       Host IRQ
> > +        +-------+            | +------+             |      controller
> > +                             |    .        +-----+  |      +-------+
> > +        +-------+            |    .        |  0  |  |----->|  GIC  |
> > +        | INTA  |----------->|    .        +-----+  |      +-------+
> > +        +-------+            |    .          .      |
> > +                             | +------+      .      |
> > +                             | | irqM |    +-----+  |
> > +                             | +------+    |  N  |  |
> > +                             |             +-----+  |
> > +                             +----------------------+
> > +
> > +Configuration of these MUXCNTL_N registers is done by a system controller
> > +(like the Device Memory and Security Controller on K3 AM654 SoC). System
> > +controller will keep track of the used and unused registers within the Router.
> > +Driver should request the system controller to get the range of GIC IRQs
> > +assigned to the requesting hosts. It is the drivers responsibility to keep
> > +track of GIC IRQs.
> > +
> > +Communication between the host processor running an OS and the system
> > +controller happens through a protocol called TI System Control Interface
> > +(TISCI protocol). For more details refer:
> > +Documentation/devicetree/bindings/arm/keystone/ti,sci.txt
> > +
> > +TISCI Interrupt Router Node:
> > +----------------------------
> > +- compatible:		Must be "ti,sci-intr".
> > +- interrupt-controller:	Identifies the node as an interrupt controller
> > +- #interrupt-cells:	Specifies the number of cells needed to encode an
> > +			interrupt source. The value should be 3.
> > +			First cell should contain the TISCI device ID of source
> > +			Second cell should contain the interrupt source offset
> > +			within the device
> > +			Third cell specifies the trigger type as defined
> > +			in interrupts.txt in this directory.
> > +- interrupt-parent:	phandle of irq parent for TISCI intr. The parent must
> > +			use the same interrupt-cells format as GIC.
> > +- ti,sci:		Phandle to TI-SCI compatible System controller node.
> > +- ti,sci-dst-id:	TISCI device ID of the destination IRQ controller.
> > +- ti,sci-rm-range-girq:	Tuple corresponding to unique TISCI resource type that
> > +			defines the dst host irq ranges assigned to this
> > +			interrupt router from this host context.
> > +			Tuple should be of format <type subtype>.
> > +
> 
> Rob, DT maintainers,
> 
> I'd like a feedback from DT maintainers on this 'range' topic.
> 
> TISCI Firmware [1] currently seems to define a type corresponding to a
> device ID[2]. in AM6 device, for example, this is different, however
> have a 1 to 1 correspondence. However, there is expectation that type will
> end up as device ID in a future SoC.
> 
> While this is subject to much debate internally, I'd like some feedback if this
> is OK from Device tree representation - it is true that Firmware does
> look at it as type, however in some future SoC, it could be that the
> values themselves may correspond one to one with a device id -> The
> original wish was that types might be something reusable across SoCs,
> but that is turning out to be more of a theoretical wish than any thing
> practical.

I'm not sure I follow all the terminology here of type, subtype, "dst 
host irq", etc. It looks to me like you should be using interrupt-map property.

Rob

> 
> [1]http://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am6x/resasg_types.html
> [2]http://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am6x/devices.html
> -- 
> Regards,
> Nishanth Menon