linux-kernel - Re: [PATCH v4 03/10] of/irq: document properties for wakeup interrupt parent

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Message-ID: <acd726c2-23fa-841a-a5c2-e00d39980021@arm.com>
Date:   Mon, 15 Apr 2019 13:42:19 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Lina Iyer <ilina@...eaurora.org>
Cc:     swboyd@...omium.org, evgreen@...omium.org,
        linux-kernel@...r.kernel.org, rplsssn@...eaurora.org,
        linux-arm-msm@...r.kernel.org, thierry.reding@...il.com,
        bjorn.andersson@...aro.org, dianders@...omium.org,
        linus.walleij@...aro.org, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v4 03/10] of/irq: document properties for wakeup interrupt
 parent

On 04/04/2019 16:58, Lina Iyer wrote:
> On Mon, Mar 18 2019 at 11:54 -0600, Marc Zyngier wrote:
>> On Wed, 13 Mar 2019 15:18:37 -0600
>> Lina Iyer <ilina@...eaurora.org> wrote:
>>
>> Please do Cc Rob when posting DT related patches.
>>
>>> Some interrupt controllers in a SoC, are always powered on and have a
>>> select interrupts routed to them, so that they can wakeup the SoC from
>>> suspend. Add wakeup-parent DT property to refer to these interrupt
>>> controllers.
>>>
>>> If the interrupts routed to the wakeup parent are not sequential, than a
>>> map needs to exist to associate the same interrupt line on multiple
>>> interrupt controllers. Providing this map in every driver is cumbersome.
>>> Let's add this in the device tree and document the properties to map the
>>> interrupt specifiers
>>>
>>> Signed-off-by: Lina Iyer <ilina@...eaurora.org>
>>> ---
>>> Changes in v4:
>>> 	- Added this documentation
>>> ---
>>>  .../interrupt-controller/interrupts.txt       | 39 +++++++++++++++++++
>>>  1 file changed, 39 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt b/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
>>> index 8a3c40829899..917b598317f5 100644
>>> --- a/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
>>> +++ b/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
>>> @@ -108,3 +108,42 @@ commonly used:
>>>  			sensitivity = <7>;
>>>  		};
>>>  	};
>>> +
>>> +3) Interrupt wakeup parent
>>> +--------------------------
>>> +
>>> +Some interrupt controllers in a SoC, are always powered on and have a select
>>> +interrupts routed to them, so that they can wakeup the SoC from suspend. These
>>> +interrupt controllers do not fall into the category of a parent interrupt
>>> +controller and can be specified by the "wakeup-parent" property and contain a
>>> +single phandle referring to the wakeup capable interrupt controller.
>>> +
>>> +   Example:
>>> +	wakeup-parent = <&pdc_intc>;
>>> +
>>> +
>>> +4) Interrupt mapping
>>> +--------------------
>>> +
>>> +Sometimes interrupts may be detected by more than one interrupt controller
>>> +(depending on which controller is active). The interrupt controllers may not
>>> +be in hierarchy and therefore the interrupt controller driver is required to
>>> +establish the relationship between the same interrupt at different interrupt
>>> +controllers. If these interrupts are not sequential then a map needs to be
>>> +specified to help identify these interrupts.
>>> +
>>> +Mapping the interrupt specifiers in the device tree can be done using the
>>> +"irqdomain-map" property. The property contains interrupt specifier at the
>>> +current interrupt controller followed by the interrupt specifier at the mapped
>>> +interrupt controller.
>>> +
>>> +   irqdomain-map = <incoming-interrupt-specifier mapped-interrupt-specifier>
>>> +
>>> +The optional properties "irqdomain-map-mask" and "irqdomain-map-pass-thru" may
>>> +be provided to help interpret the valid bits of the incoming and mapped
>>> +interrupt specifiers respectively.
>>> +
>>> +   Example:
>>> +	irqdomain-map = <22 0 &intc 36 0>, <24 0 &intc 37 0>;
>>> +	irqdomain-map-mask = <0xff 0>;
>>> +	irqdomain-map-pass-thru = <0 0xff>;
>>
>>
>> This doesn't quite explain how the mask and pass-thru properties are
>> used. I guess that the mask is used to define the 'useful bits' on the
>> incoming side, but pass-thru puzzles me. In your example, does it mean
>> that incoming lines map to outgoing interrupt <0 0>?
>>
> Sorry about the late reply.
> 
> How about this to go with the rest of the documentation -
> 
> In the above example, the input interrupt specifier map-mask <0xff 0> applied
> on the incoming interrupt specifier of the map <22 0>, <24 0>, returns the
> input interrupt 22, 24 etc. The second argument being irq type is immaterial
> from the map and is used from the incoming request instead. The pass-thru
> specifier parses the output interrupt specifier from the rest of the unparsed
> argments from the map <&intc 36 0>, <&intc 37 0> etc to return the output
> interrupt 36, 37 etc.

I think you need to add #interrupt-cells in your example, which is
otherwise hard to interpret.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...