linux-kernel - Re: [PATCH v3 4/4] iio: magnetometer: ak8975: Add gpio reset support

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Date:   Tue, 19 May 2020 15:03:50 +0200
From:   Jonathan Albrieux <jonathan.albrieux@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hartmut Knaack <knaack.h@....de>,
        Jilayne Lovejoy <opensource@...ayne.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        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>,
        Steve Winslow <swinslow@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Cameron <jic23@...nel.org>,
        Allison Randal <allison@...utok.net>
Subject: Re: [PATCH v3 4/4] iio: magnetometer: ak8975: Add gpio reset support

On Tue, May 19, 2020 at 03:57:13PM +0300, Andy Shevchenko wrote:
> On Tue, May 19, 2020 at 02:43:54PM +0200, Jonathan Albrieux wrote:
> > According to AK09911 datasheet, if reset gpio is provided then
> > 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.
> 
> Wrong position of (), but hold on, this is so minor, no need to send a new
> version because of this.
>

Ops, if this represents a problem I can fix it, there's absolutely no problem!
 
> > 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.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
> > Signed-off-by: Jonathan Albrieux <jonathan.albrieux@...il.com>
> > ---
> >  drivers/iio/magnetometer/ak8975.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> > index fd368455cd7b..a23422aad97d 100644
> > --- a/drivers/iio/magnetometer/ak8975.c
> > +++ b/drivers/iio/magnetometer/ak8975.c
> > @@ -358,6 +358,7 @@ struct ak8975_data {
> >  	u8			asa[3];
> >  	long			raw_to_gauss[3];
> >  	struct gpio_desc	*eoc_gpiod;
> > +	struct gpio_desc	*reset_gpiod;
> >  	int			eoc_irq;
> >  	wait_queue_head_t	data_ready_queue;
> >  	unsigned long		flags;
> > @@ -384,6 +385,9 @@ static int ak8975_power_on(const struct ak8975_data *data)
> >  			 "Failed to enable specified Vid supply\n");
> >  		return ret;
> >  	}
> > +
> > +	gpiod_set_value_cansleep(data->reset_gpiod, 0);
> > +
> >  	/*
> >  	 * According to the datasheet the power supply rise time is 200us
> >  	 * and the minimum wait time before mode setting is 100us, in
> > @@ -396,6 +400,8 @@ static int ak8975_power_on(const struct ak8975_data *data)
> >  /* Disable attached power regulator if any. */
> >  static void ak8975_power_off(const struct ak8975_data *data)
> >  {
> > +	gpiod_set_value_cansleep(data->reset_gpiod, 1);
> > +
> >  	regulator_disable(data->vid);
> >  	regulator_disable(data->vdd);
> >  }
> > @@ -839,6 +845,7 @@ static int ak8975_probe(struct i2c_client *client,
> >  	struct ak8975_data *data;
> >  	struct iio_dev *indio_dev;
> >  	struct gpio_desc *eoc_gpiod;
> > +	struct gpio_desc *reset_gpiod;
> >  	const void *match;
> >  	unsigned int i;
> >  	int err;
> > @@ -856,6 +863,16 @@ static int ak8975_probe(struct i2c_client *client,
> >  	if (eoc_gpiod)
> >  		gpiod_set_consumer_name(eoc_gpiod, "ak_8975");
> >  
> > +	/*
> > +	 * According to AK09911 datasheet, if reset GPIO is provided then
> > +	 * deassert reset on ak8975_power_on() and assert reset on
> > +	 * ak8975_power_off().
> > +	 */
> > +	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
> 
> 

Best regards,
Jonathan Albrieux