Re: [PATCH V2 1/3] dt: palmas: support IRQ inversion at the board level

[Graeme Gregory <graeme-/SyDAi3Rz4f10XsdtD+oqA@public.gmane.org>]

On Thu, Feb 27, 2014 at 01:51:19PM -0700, Stephen Warren wrote:
> From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> 
> Some boards or SoCs have an inverter between the PMIC IRQ output pin and
> the IRQ controller input signal.
> 
> The IRQ specifier in DT is meant to represent the IRQ flags at the input
> to the IRQ controller.
> 
> The Palmas HW's IRQ output has configurable polarity. Software needs to
> know which polarity to choose for the IRQ output. Software may be tempted
> to extract the IRQ polarity from the IRQ specifier in order to make this
> choice.
> 
> That approach works fine if the IRQ signal is routed directly from the
> PMIC to the IRQ controller with no intervening logic. However, if the
> signal is inverted between the two, this approach gets the wrong answer.
> 
> Add an additional optional DT property which indicates that such an
> inversion occurs. This allows DT to give complete information about the
> desired IRQ output polarity to software.
> 
> An alternative would have been to add a new non-optional DT parameter to
> indicate the exact desired output polarity. However, this would have been
> an incompatible change to the DT binding.
> 
> Signed-off-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> Acked-by: Laxman Dewangan <ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> Acked-by: Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
> v2: Split V1's patch 1/2 into separate patches 1/3 and 2/3.
> ---
>  Documentation/devicetree/bindings/mfd/palmas.txt | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mfd/palmas.txt b/Documentation/devicetree/bindings/mfd/palmas.txt
> index e5f0f8303461..76ec509d5f87 100644
> --- a/Documentation/devicetree/bindings/mfd/palmas.txt
> +++ b/Documentation/devicetree/bindings/mfd/palmas.txt
> @@ -18,6 +18,12 @@ Required properties:
>    ti,tps659038
>  and also the generic series names
>    ti,palmas
> +- interrupts : Should contain a single entry for the IRQ output.
> +- ti,irq-externally-inverted : If missing, the polarity of the Palmas IRQ
> +  output should be set to the opposite of the polarity indicated by the IRQ
> +  specifier in the interrupts property. If absent, the polarity should be
> +  configured to match. This allows the representation of an inverter between
> +  the Palmas IRQ output and the interrupt parent's IRQ input.

This has got to be the wrong way to do things, all this leads to is every
device doing this property in its own way and having totally inconsistent
properties all meaning the same thing.

If there is some other hardware inverting lines then there should be
a generic binding for this in DT. This is not describing the palmas hardware
but some external object to the palmas.

Graeme

>  - interrupt-controller : palmas has its own internal IRQs
>  - #interrupt-cells : should be set to 2 for IRQ number and flags
>    The first cell is the IRQ number.
> -- 
> 1.8.1.5
> 
> 
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