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SubjectRe: [PATCH 1/2] dt-bindings: irqchip: Introduce TISCI Interrupt router bindings
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On Monday 08 October 2018 07:25 PM, Marc Zyngier wrote:
> On 08/10/18 10:46, Lokesh Vutla wrote:
>> Hi Marc,
>>
>> On Saturday 06 October 2018 03:32 PM, Marc Zyngier wrote:
>>> On Sat, 06 Oct 2018 08:28:11 +0100,
>>> Lokesh Vutla <lokeshvutla@ti.com> 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.
>>>
>>> I would drop the GIC here, and replace it by "parent interrupt
>>> controller", as nothing here is GIC specific
>>>
>>>> +
>>>> +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.
>>>
>>> Are all trigger types supported?
>>
>> Nope, only level interrupts are supported. Will fix it in v2.
>>
>>>
>>>> +- interrupt-parent: phandle of irq parent for TISCI intr. The parent must
>>>> + use the same interrupt-cells format as GIC.
>>>
>>> Why that constraint? From what I can see, the two are fairly
>>> independent, and the constraint looks more of a Linux driver issue
>>> than a DT constraint.
>>
>> Driver when calling irq_domain_alloc_irqs_parent(), the fwspec node that gets
>> passed assumes that parent is gic. parameters are filled in with such
>> assumption. Do you suggest anything to make it more generic?
>
> As I said, that's a Linux driver issue, not a DT specification at all.
> It is not worth it trying to generalize it in the driver implementation,
> but the DT spec it self should be generic enough.

okay, will fix 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: 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>.
>>>> +
>>
>> Thanks a lot for the review. Also, I need a suggestion regarding one more
>> interrupt controller(Interrupt Aggregator) on the same SoC controlled by
>> TISCI_PROTOCOL.
>>
>> The Interrupt Aggregator (INTA) provides a centralized machine
>> which handles the termination of system events to that they can
>> be coherently processed by the host(s) in the system. Integration looks
>> something similar https://pastebin.ubuntu.com/p/T32vbrwsch/ .
>>
>> Configuration of the Intmap registers that maps global events to vint is done
>> by a system controller (like the Device Memory and Security Controller on K3
>> AM654 SoC). Driver should request the system controller to get the range
>> of global events and vints assigned to the requesting host. Management
>> of these requested resources should be handled by driver and requests
>> system controller to map specific global event to vint, bit pair.
>
> I'm sorry, but I really have no idea what the global events and the
> vints are. Maybe you should describe what this is all about, and maybe
> provide a pointer to some documentation...

Sorry I should have done that earlier. TRM is available here[1], Section 9.3
talks about Interrupt Router, Section 10.2.7 talks about Interrupt aggregator.
Documentation for TISCI IRQ management is available here[2].


[1] http://www.ti.com/lit/ug/spruid7a/spruid7a.pdf
[2] http://downloads.ti.com/tisci/esd/latest/2_tisci_msgs/rm/rm_irq.html

>
>>
>> There can be cases such that IRQ routes can involve both INTR and INTA like below:
>> IP ---> INTA ---> INTR ----> GIC.
>>
>> In these cases TISCI involves only one message with parametes(source id, source
>> offset, inta_id, dst id) for configuring IRQ route till the destination. Co
>> processor will detect there is INTR in the IRQ path and configure that as well.
>>
>> Right now I kind of differentiated this scenario in INTA driver by passing a
>> flag(TI_SCI_EVENT) to INTR driver. If such flag comes, INTR driver should avoid
>> calling ti_sci api for configuring. Do you think this is the right direction or
>> do you suggest a better solution.
>
> Frankly, it mostly indicates that the firmware does too much, and should
> be more flexible.
>
>> If I am not clear in the above description, I can post an RFC for INTA driver
>> for continuing this discussion.
>
> That'd be preferable, IMO. Please provide definitions for all the above

Sure, will try to post the consolidated series asap. Thanks a lot for the help.

Regards,
Lokesh

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