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

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Date:   Tue, 19 May 2020 11:44:18 +0200
From:   Jonathan Albrieux <jonathan.albrieux@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.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 12:21:27PM +0300, Andy Shevchenko wrote:
> On Tue, May 19, 2020 at 08:57:43AM +0200, Jonathan Albrieux wrote:
> 
> Thanks for an update, my comments below.
> 

Thanks to you for taking time to review the code!

> > 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.
> 

Ok I will separate the patch

> > +	/*
> > +	 * 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.
> 

Will fix this as like as the other changes you pointed out about periods and
trailing spaces as soon as possible

> > +	 */
> > +	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
> 
> 

Again, thank you,
Best regards,
Jonathan Albrieux