linux-kernel - Re: [PATCH 1/2] mfd: arizona: Add GPIO maintain state flag

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Date:   Mon, 10 Apr 2017 15:17:58 -0500
From:   Rob Herring <robh@...nel.org>
To:     Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Cc:     linus.walleij@...aro.org, lee.jones@...aro.org, gnurou@...il.com,
        mark.rutland@....com, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...nsource.wolfsonmicro.com
Subject: Re: [PATCH 1/2] mfd: arizona: Add GPIO maintain state flag

On Fri, Apr 07, 2017 at 01:38:44PM +0100, Charles Keepax wrote:
> The Arizona devices only maintain the state of output GPIOs whilst the
> CODEC is active, this can cause issues if the CODEC suspends whilst
> something is relying on the state of one of its GPIOs. However, in
> many systems the CODEC GPIOs are used for audio related features
> and thus the state of the GPIOs is unimportant whilst the CODEC is
> suspended. Often keeping the CODEC resumed in such a system would
> incur a power impact that is unacceptable.
> 
> Add a flag through the second cell of the GPIO specifier in device
> tree, to allow the user to select whether a GPIO being configured as
> an output should keep the CODEC resumed.

If the whole codec can't be suspended, why does this need to be per 
GPIO? You could just have a single boolean property.

> 
> Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> ---
>  Documentation/devicetree/bindings/mfd/arizona.txt | 5 ++++-
>  include/dt-bindings/mfd/arizona.h                 | 3 +++
>  2 files changed, 7 insertions(+), 1 deletion(-)