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

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Message-ID: <20190404155838.GD10883@codeaurora.org>
Date:   Thu, 4 Apr 2019 09:58:38 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Marc Zyngier <marc.zyngier@....com>
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 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.


--Lina