linux-kernel - Re: [PATCH v2 3/3] iio: magnetometer: ak8975: Add gpio reset support

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Message-ID: <20200519092127.GS1634618@smile.fi.intel.com>
Date:   Tue, 19 May 2020 12:21:27 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jonathan Albrieux <jonathan.albrieux@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hartmut Knaack <knaack.h@....de>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@...r.kernel.org>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Cameron <jic23@...nel.org>,
        Jilayne Lovejoy <opensource@...ayne.com>
Subject: Re: [PATCH v2 3/3] iio: magnetometer: ak8975: Add gpio reset support

On Tue, May 19, 2020 at 08:57:43AM +0200, Jonathan Albrieux wrote:

Thanks for an update, my comments below.

> According to AK09911 datasheet, if reset gpio is provided then 

Trailing whitespace.

> deassert reset on ak8975_power_on and assert reset on ak8975_power_off.
> 
> Without reset's deassertion during ak8975_power_on, driver's probe fails on
> ak8975_who_i_am while checking for device identity for AK09911 chip
> 
> AK09911 has an active low reset gpio to handle register's reset.
> AK09911 datasheed says that, if not used, reset pin should be connected
> to VID. This patch emulates this situation

Please, put periods at the end of the phrases.

>  	/*
> -	 * According to the datasheet the power supply rise time i 200us
> +	 * According to the datasheet the power supply rise time is 200us
>  	 * and the minimum wait time before mode setting is 100us, in
> -	 * total 300 us. Add some margin and say minimum 500us here.
> +	 * total 300us. Add some margin and say minimum 500us here.
>  	 */

This is not related change (perhaps, you may do in separate patch), but I'm not
against it. Up to maintainer.

> +	/*
> +	 * According to AK09911 datasheet, if reset gpio is provided then
> +	 * deassert reset on ak8975_power_on and assert reset on
> +	 * ak8975_power_off.

We try to refer to the code accordingly to the kernel doc recommendations (even
for non-kdoc comments). So, here, 'function' as 'function()' (without quotes)
and so on.

> +	 */
> +	reset_gpiod = devm_gpiod_get_optional(&client->dev,
> +					      "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(reset_gpiod))
> +		return PTR_ERR(reset_gpiod);
> +
>  	/* Register with IIO */
>  	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
>  	if (indio_dev == NULL)
> @@ -866,6 +883,7 @@ static int ak8975_probe(struct i2c_client *client,
>  
>  	data->client = client;
>  	data->eoc_gpiod = eoc_gpiod;
> +	data->reset_gpiod = reset_gpiod;
>  	data->eoc_irq = 0;
>  
>  	err = iio_read_mount_matrix(&client->dev, "mount-matrix", &data->orientation);
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko