Re: [PATCH v2 06/10] dt-bindings: irqchip: Introduce TISCI Interrupt router bindings

Lokesh Vutla
2018-10-26T06:39:56Z

Hi Rob,

On Friday 26 October 2018 12:15 AM, Rob Herring wrote:
> On Thu, Oct 18, 2018 at 09:10:13PM +0530, Lokesh Vutla wrote:
>> Add the DT binding documentation for Interrupt router driver.
>>
>> Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
>> ---
>> Changes since v1:
>> - Drop dependency on GIC
>> - Updated supported interrupt types.
>>
>> .../interrupt-controller/ti,sci-intr.txt | 81 +++++++++++++++++++
>> MAINTAINERS | 1 +
>> 2 files changed, 82 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..276bb4f0ad12
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
>> @@ -0,0 +1,81 @@
>> +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 | |----->| IRQ |
>> + | 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 Host 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. Only level
>> + sensitive trigger types are supported.
>> +- interrupt-parent: phandle of irq parent for TISCI intr.
>
> This is implied and could be in a parent node.

okay, will drop it in next version.

>
>> +- 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: TISCI subtype id representing the host irqs assigned
>> + to this interrupt router.
>
> These need a better explanation and there's still some questions on v1
> asked of me that I tried to answer.

Before I jump into the details, I would like to provide a brief on TISCI
resource management:

- Host_id: Typically it is the representation of the host processing entities
(example: A53 cores running in a VM) as identified by the TISCI.[1]
- Device_id: Each Device in SoC is uniquely identified by TISCI using an ID.
- Each device has Resources like interrupts, DMA channels etc. A simple example
would be Interrupt Router and GIC($subject). There are n physical GIC interrupts
connected to Interrupt Router. Such resources are are uniquely identified by
TISCI using a type ID.[2]

For the sake of simplicity lets consider an Interrupt Router(IR) to which GIC
line 32-63 are connected. Considering Isolation for each VM in picture, TISCI
allows for a certain range within [32-63] to be assigned to a specific Host_ID.
This is mainly to provide the ability for OSs running in virtual machines to be
able to independently communicate with the firmware without the need going
through a hypervisor.

- Now for Linux to know the GIC irq range that can be used by this Interrupt
router, IR driver should send a message to system-controller using TISCI
protocol with the resource type as parameter.
- For configuring the IRQ,(i.e. attaching an input to IR to a GIC irq), IR
driver should send a message to system-controller using TISCI protocol with
gic-device-id and an irq from the provided range as parameters.

For covering the above two scenarios, ti,sci-dst-id and ti,sci-rm-range-girq is
introduced in DT.

[1] http://downloads.ti.com/tisci/esd/latest/5_soc_doc/am6x/hosts.html
[2] http://downloads.ti.com/tisci/esd/latest/5_soc_doc/am6x/resasg_types.html

>
>> +
>> +Example:
>> +--------
>> +The following example demonstrates both interrupt router node and the consumer
>> +node(main gpio) on the AM654 SoC:
>> +
>> +main_intr: interrupt-controller@1 {
>> + compatible = "ti,sci-intr";
>> + interrupt-controller;
>> + interrupt-parent = <&gic>;
>> + #interrupt-cells = <3>;
>> + ti,sci = <&dmsc>;
>> + ti,sci-dst-id = <56>;
>> + ti,sci-rm-range-girq = <0x1>;
>> +};
>> +
>> +main_gpio0: main_gpio0@600000 {
>
> gpio@...

Sure, will fix it in next version.

Thanks and regards,
Lokesh