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

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Message-ID: <20190318174236.072f0a95@why.wild-wind.fr.eu.org>
Date:   Mon, 18 Mar 2019 17:42:36 +0000
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 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>?

Thanks,

	M.
-- 
Without deviation from the norm, progress is not possible.