linux-kernel - Re: [PATCH] gpio: pca953x: Add optional reset gpio control

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Message-ID: <84d21f6d-7d6b-dd05-98a1-739c1e4d8d58@gmail.com>
Date:   Tue, 10 Jan 2017 11:10:23 -0800
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH] gpio: pca953x: Add optional reset gpio control

On 01/04/2017 02:31 AM, Andy Shevchenko wrote:
>
>>>> +               reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
>>>> +                                                    GPIOD_OUT_LOW);
>>> Shouldn't be _optional_exclusive?
>>> See this recent discussion https://patchwork.ozlabs.org/patch/706002/
>> There is no devm_gpiod_get_optional_exclusive(), probably you confuse
>> the function with devm_reset_control_get_optional_exclusive().
> Perhaps it's time to add
> drivers/reset/reset-gpio.c ?

Yeah, looks like a GPIO based reset controller driver would need to be
implemented in order to go this route. The max7310 nodes in
imx6qdl-sabreauto.dtsi could then refer to that reset controller by the
'resets' phandle.

There are many many devices that would benefit from a GPIO reset
controller, I count 143 nodes under arch/arm/boot/dts that specify a
'reset-gpios' property.

But I don't have the time to write such a driver. So I would propose just
keeping the devm_gpiod_get_optional() call here. When such a gpio reset
controller is written, the work can begin to convert all the gpio reset 
users
to make use of it.

Steve