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

From: Lokesh Vutla
Date: Fri Oct 26 2018 - 02:46:25 EST

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@xxxxxx>
Changes since v1:
- Drop dependency on GIC
- Updated supported interrupt types.

.../interrupt-controller/ti,sci-intr.txt | 81 +++++++++++++++++++
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:
+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.


+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 {


Sure, will fix it in next version.

Thanks and regards,