On Thu, Dec 23, 2010 at 12:51:29AM -0600, Meador Inge wrote:
> Hi All,
>
> I am currently doing some work on Linux PPC AMP systems (with Hollis,
> CC'd). We are using device trees to partition resources between the
> different OSes. To help with this effort, we would like to introduce
> some new bindings to the MPIC.
>
> Currently, there are no bindings for the MPIC under
> '.../Documentation/powerpc/dts-bindings/'. I think most folks are
> following the IEEE 1275 bindings for Open PIC.
>
> It would be nice to check-in a binding for the MPIC that is a superset
> of the 1275 bindings as a place to document extensions. The already in
> use property 'protected-sources', for example, could be placed there.
>
> I have included a draft proposal of what this would like. It includes
> some properties ('no-reset') and a node (for message registers) that we
> are currently using for our AMP implementation and we would really
> like to push upstream. If the general idea seems sound, then I will
> clean up the proposal and submit a patch for the bindings.
>
> Thoughts?
Hi Meador. Comments below.
g.
>
> ===============
>
> * MPIC Binding
>
> This binding specifies what properties and child nodes must be
> available on the device tree representation of the MPIC interrupt
> controller. This binding is a superset of the binding defined for
> Open PIC in [1].
>
> ** Required properties:
>
> - All of the required properties mentioned in [1].
You should probably list them here anyway to aid the reader.
>
> ** Optional properties:
>
> - no-reset : the presence of this property indicates that the
> interrupt controller should not be reset during OS
> initialization.
> - protected-sources : a list of interrupt sources that are not
> available for use.
What is the use case for the protected-sources property? Wouldn't the
irqs simply not be referenced by any device nodes? Documenting the
reason for this property would be useful here.
>
> ** Example:
>
> mpic: p...@40000 {
> interrupt-controller;
> #address-cells = <0>;
> #interrupt-cells = <2>;
> reg = <0x40000 0x40000>;
> compatible = "chrp,open-pic";
> device_type = "open-pic";
> protected-sources = <0xb1 0xb2>;
> no-reset;
> };
>
> * MPIC Message Registers
>
> This binding specifies how the MPIC message registers implemented on
> some Freescale platforms for interprocessor communication should be
> represented.
>
> ** Required parent:
>
> - Message register nodes should always been nested under a MPIC
> node.
>
> ** Required properties:
>
> - compatible : compatible list, contains 2 entries, first is
> "fsl,CHIP-msgr", where CHIP is the processor
> (p2020, mpc8572, etc ...) and the second is
> "fsl,mpic-msgr".
I'd rather see the 'generic' value of mpic-msgr omitted and instead
allow new parts to claim compatibility with an older chip. Generic
or wildcard compatible values can be troublesome because the meaning
has a tendency to change over time.
> - reg : should contain the address and the length of the
> message register block.
> - cell-index : the index of the message register block.
? This needs some more explanation. cell-index often gets abused as
a way to enumerate devices. Typically, the address of the device
itself is sufficient to identify the device.
> - interrupts : each one of the interrupts here represents the
> interrupt line for one message register. These
> interrupts are routed internally to the MPIC.
>
> NOTE: The 'interrupt-parent' is implicit since message register nodes
> are always children of interrupt controller nodes.
>
> ** Example:
>
> mpic: p...@40000 {
> interrupt-controller;
> #address-cells = <0>;
> #interrupt-cells = <2>;
> reg = <0x40000 0x40000>;
> compatible = "chrp,open-pic";
> device_type = "open-pic";
> protected-sources = <0xb1>;
>
> m...@1400 {
> compatible = "fsl,p2020-msgr", "fsl,mpic-msgr";
> reg = <0x1400 0x200>;
Are these registers memory mapped? If so, then the parent node
needs to have a 'ranges' property.
> cell-index = <0>;
> interrupts = <0xb0 0x2 0xb1 0x2
> 0xb2 0x2 0xb3 0x2>;
> };
>
> m...@2400 {
> compatible = "fsl,p2020-msgr", "fsl,mpic-msgr";
> reg = <0x2400 0x200>;
> cell-index = <1>;
> interrupts = <0xb4 0x2 0xb5 0x2
> 0xb6 0x2 0xb7 0x2>;
> };
> };
>
> * References
>
> [1] PowerPC Microprocessor Common Hardware Reference Platform (CHRP)
> Binding, Version 1.8, 1998. Published by the Open Firmware Working
> Group. (http://playground.sun.com/1275/bindings/chrp/chrp1_8a.ps)
>
>
> --
> Meador Inge | meador_inge AT mentor.com
> Mentor Embedded | http://www.mentor.com/embedded-software
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
