linux-kernel - Re: [PATCH v2 1/5] dt-bindings: interrupt-controller: Update STM32 EXTI interrupt controller

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Message-ID: <e5754264-b263-1090-3017-1a6fec284614@foss.st.com>
Date:   Tue, 4 Jan 2022 18:14:14 +0100
From:   Alexandre TORGUE <alexandre.torgue@...s.st.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Rob Herring <robh@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] dt-bindings: interrupt-controller: Update STM32
 EXTI interrupt controller

Hi Marc

On 12/20/21 1:34 PM, Marc Zyngier wrote:
> On Fri, 17 Dec 2021 13:39:11 +0000,
> Alexandre TORGUE <alexandre.torgue@...s.st.com> wrote:
>>
>> On 12/16/21 9:15 PM, Rob Herring wrote:
>>> On Wed, Dec 15, 2021 at 11:58:43AM +0100, Alexandre Torgue wrote:
>>>> Document new entry "st,exti-mapping" which links EXTI lines with GIC
>>>> interrupt lines and add an include file to define EXTI interrupt type.
>>>>
>>>> Signed-off-by: Alexandre Torgue <alexandre.torgue@...s.st.com>
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/interrupt-controller/st,stm32-exti.yaml b/Documentation/devicetree/bindings/interrupt-controller/st,stm32-exti.yaml
>>>> index d19c881b4abc..e08bb51e97a8 100644
>>>> --- a/Documentation/devicetree/bindings/interrupt-controller/st,stm32-exti.yaml
>>>> +++ b/Documentation/devicetree/bindings/interrupt-controller/st,stm32-exti.yaml
>>>> @@ -41,6 +41,17 @@ properties:
>>>>        description:
>>>>          Interrupts references to primary interrupt controller
>>>>    +  st,exti-mapping:
>>>> +    $ref: "/schemas/types.yaml#/definitions/uint32-matrix"
>>>> +    description: |
>>>> +            Define mapping between EXTI lines and GIC irq lines. Should be:
>>>> +            st,exti-mapping = <EXTI_LINE GIC_IRQ EXTI_TYPE>, ...;
>>>> +            With:
>>>> +            - EXTI_LINE: EXTI line number.
>>>> +            - GIC_IRQ: GIC IRQ associated to the EXTI line.
>>>> +            - EXTI_TYPE: STM32_EXTI_TYPE_CONFIGURABLE or STM32_EXTI_TYPE_DIRECT.
>>>> +              Defined in include/dt-bindings/interrupt-controller/stm32-exti.h
>>>
>>> No custom properties for this. See[1][2][3].
>>>
>>
>> Thanks for inputs. In my case the mapping consists to map an EXTI line
>> with a GIC irq line which could be done using interrupt-map (avoiding
>> to parse it in my driver).
> 
> The problem is that 'interrupt-map' defines an interrupt mapping
> between an input and an output, and that mentioning the GIC in such a
> table will only result in your EXTI to be bypassed.
> 
> 'interrupt-map' really is a dispatch table for targeting an interrupt
> controller (or multiple controllers, even), but really isn't the
> correct tool to carry configuration informations to an interrupt
> controller driver.

Ok so let's forget "interrupt-map"

>> But for each EXTI/GIC association I would
>> like also to describe the EXTI_TYPE (which actually describe the well
>> irqchip to use inside my exti driver) . This property is not generic
>> and so I assume I can't use a generic binding such "interrupt-map".
>>
>> If the solution consists to use a common binding (i.e. interrupt-map)
>> plus a conversion table in exti driver to affect the well irq_chip to
>> the well EXTI line then we could envisage to keep the whole mapping
>> inside the driver (even if it's not the best solution).
> 
> A possible solution would be to have:
> 
> - A set of standard 'interrupts' properties describing the output
> signals
> 
> - A set of properties describing the input to output mapping (if
> relevant) and additional configuration information that for the
> interrupt controller driver.

Does it means to have my own description of "interrupt" property using 
xlate function in EXTI driver ?

something like that:

interrupt = <GIC_SPI 6 EXTI_LINE EXTI_TYPE>, ...

regards
Alex
> 
> 	M.
>