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Date:   Mon, 18 Feb 2019 14:48:05 +0000
From:   Jonathan Cameron <jonathan.cameron@...wei.com>
To:     Renato Lui Geh <renatogeh@...il.com>
CC:     Jonathan Cameron <jic23@...nel.org>, <lars@...afoo.de>,
        <Michael.Hennerich@...log.com>, <knaack.h@....de>,
        <pmeerw@...erw.net>, <gregkh@...uxfoundation.org>,
        <stefan.popa@...log.com>, <alexandru.Ardelean@...log.com>,
        <giuliano.belinassi@....br>, <linux-iio@...r.kernel.org>,
        <devel@...verdev.osuosl.org>, <linux-kernel@...r.kernel.org>,
        <kernel-usp@...glegroups.com>
Subject: Re: [PATCH v3 1/4] staging: iio: ad7780: add gain & filter gpio
 support

On Thu, 14 Feb 2019 18:31:12 -0200
Renato Lui Geh <renatogeh@...il.com> wrote:

> Hi Jonathan,
> 
> Thanks for the review. Comments inline.
> 
> Renato
> 
> On 02/09, Jonathan Cameron wrote:
> >On Tue, 5 Feb 2019 15:13:00 -0200
> >Renato Lui Geh <renatogeh@...il.com> wrote:
> >  
> >> Previously, the AD7780 driver only supported gpio for the 'powerdown'
> >> pin. This commit adds suppport for the 'gain' and 'filter' pin.
> >>
> >> Signed-off-by: Renato Lui Geh <renatogeh@...il.com>
> >> Signed-off-by: Giuliano Belinassi <giuliano.belinassi@....br>
> >> Co-developed-by: Giuliano Belinassi <giuliano.belinassi@....br>  
> >Comments inline.
> >  
> >> ---
> >> Changes in v3:
> >> 	- Renamed ad7780_chip_info's filter to odr
> >> 	- Renamed ad778x_filter to ad778x_odr_avail
> >> 	- Changed vref variable from unsigned int to unsigned long long to
> >> 	  avoid overflow
> >> 	- Removed unnecessary AD_SD_CHANNEL macro
> >>
> >>  drivers/staging/iio/adc/ad7780.c | 95 ++++++++++++++++++++++++++++++--
> >>  1 file changed, 89 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/staging/iio/adc/ad7780.c b/drivers/staging/iio/adc/ad7780.c
> >> index c4a85789c2db..6e4357800d31 100644
> >> --- a/drivers/staging/iio/adc/ad7780.c
> >> +++ b/drivers/staging/iio/adc/ad7780.c
> >> @@ -39,6 +39,15 @@
> >>  #define AD7170_PATTERN		(AD7780_PAT0 | AD7170_PAT2)
> >>  #define AD7170_PATTERN_MASK	(AD7780_PAT0 | AD7780_PAT1 | AD7170_PAT2)
> >>
> >> +#define AD7780_GAIN_GPIO	0
> >> +#define AD7780_FILTER_GPIO	1  
> >What are these for?  
> 
> Sorry about that. That's leftover from a previous attempt.
> >  
> >> +
> >> +#define AD7780_GAIN_MIDPOINT	64
> >> +#define AD7780_FILTER_MIDPOINT	13350
> >> +
> >> +static const unsigned int ad778x_gain[2]      = { 1, 128 };
> >> +static const unsigned int ad778x_odr_avail[2] = { 10000, 16700 };
> >> +
> >>  struct ad7780_chip_info {
> >>  	struct iio_chan_spec	channel;
> >>  	unsigned int		pattern_mask;
> >> @@ -50,7 +59,11 @@ struct ad7780_state {
> >>  	const struct ad7780_chip_info	*chip_info;
> >>  	struct regulator		*reg;
> >>  	struct gpio_desc		*powerdown_gpio;
> >> -	unsigned int	gain;
> >> +	struct gpio_desc		*gain_gpio;
> >> +	struct gpio_desc		*filter_gpio;
> >> +	unsigned int			gain;
> >> +	unsigned int			odr;
> >> +	unsigned int			int_vref_mv;
> >>
> >>  	struct ad_sigma_delta sd;
> >>  };
> >> @@ -104,17 +117,65 @@ static int ad7780_read_raw(struct iio_dev *indio_dev,
> >>  		voltage_uv = regulator_get_voltage(st->reg);
> >>  		if (voltage_uv < 0)
> >>  			return voltage_uv;
> >> -		*val = (voltage_uv / 1000) * st->gain;
> >> +		voltage_uv /= 1000;
> >> +		*val = voltage_uv * st->gain;
> >>  		*val2 = chan->scan_type.realbits - 1;
> >> +		st->int_vref_mv = voltage_uv;
> >>  		return IIO_VAL_FRACTIONAL_LOG2;
> >>  	case IIO_CHAN_INFO_OFFSET:
> >>  		*val = -(1 << (chan->scan_type.realbits - 1));
> >>  		return IIO_VAL_INT;
> >> +	case IIO_CHAN_INFO_SAMP_FREQ:
> >> +		*val = st->odr;
> >> +		return IIO_VAL_INT;
> >>  	}
> >>
> >>  	return -EINVAL;
> >>  }
> >>
> >> +static int ad7780_write_raw(struct iio_dev *indio_dev,
> >> +			    struct iio_chan_spec const *chan,
> >> +			    int val,
> >> +			    int val2,
> >> +			    long m)
> >> +{
> >> +	struct ad7780_state *st = iio_priv(indio_dev);
> >> +	const struct ad7780_chip_info *chip_info = st->chip_info;
> >> +	unsigned long long vref;
> >> +	unsigned int full_scale, gain;
> >> +
> >> +	if (!chip_info->is_ad778x)
> >> +		return 0;
> >> +
> >> +	switch (m) {
> >> +	case IIO_CHAN_INFO_SCALE:
> >> +		if (val != 0)
> >> +			return -EINVAL;
> >> +
> >> +		vref = st->int_vref_mv * 1000000LL;
> >> +		full_scale = 1 << (chip_info->channel.scan_type.realbits - 1);
> >> +		gain = DIV_ROUND_CLOSEST(vref, full_scale);
> >> +		gain = DIV_ROUND_CLOSEST(gain, val2);
> >> +		st->gain = gain;
> >> +		if (gain < AD7780_GAIN_MIDPOINT)
> >> +			gain = 0;
> >> +		else
> >> +			gain = 1;
> >> +		gpiod_set_value(st->gain_gpio, gain);
> >> +	break;
> >> +	case IIO_CHAN_INFO_SAMP_FREQ:
> >> +		if (1000*val + val2/1000 < AD7780_FILTER_MIDPOINT)
> >> +			val = 0;
> >> +		else
> >> +			val = 1;
> >> +		st->odr = ad778x_odr_avail[val];
> >> +		gpiod_set_value(st->filter_gpio, val);
> >> +	break;
> >> +	}
> >> +
> >> +	return 0;
> >> +}
> >> +
> >>  static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta,
> >>  				     unsigned int raw_sample)
> >>  {
> >> @@ -126,10 +187,8 @@ static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta,
> >>  		return -EIO;
> >>
> >>  	if (chip_info->is_ad778x) {
> >> -		if (raw_sample & AD7780_GAIN)
> >> -			st->gain = 1;
> >> -		else
> >> -			st->gain = 128;
> >> +		st->gain = ad778x_gain[raw_sample & AD7780_GAIN];
> >> +		st->odr = ad778x_odr_avail[raw_sample & AD7780_FILTER];
> >>  	}
> >>
> >>  	return 0;
> >> @@ -173,6 +232,7 @@ static const struct ad7780_chip_info ad7780_chip_info_tbl[] = {
> >>
> >>  static const struct iio_info ad7780_info = {
> >>  	.read_raw = ad7780_read_raw,
> >> +	.write_raw = ad7780_write_raw,
> >>  };
> >>
> >>  static int ad7780_probe(struct spi_device *spi)
> >> @@ -222,6 +282,29 @@ static int ad7780_probe(struct spi_device *spi)
> >>  		goto error_disable_reg;
> >>  	}
> >>
> >> +	if (st->chip_info->is_ad778x) {
> >> +		st->gain_gpio = devm_gpiod_get_optional(&spi->dev,
> >> +							"gain",  
> >
> >These are not particularly standard names (basically not "reset"),
> >so they should be vendor prefixed, so that people know to go
> >look at the device specific binding.  
> 
> I see. Should they be something like "adi,gain" and "adi,filter"? Am I
> correct to assume that I'll have to somehow mention these in the
> dt-binding?
yes and yes - name is just adi,gain-gpios rather than gain-gpios.

Take a look at the other drivers doing the same thing.  We used to
be more lax on this so there are drivers without the prefixes, but
can't fix them now.

Jonathan

> >  
> >> +							GPIOD_OUT_HIGH);
> >> +		if (IS_ERR(st->gain_gpio)) {
> >> +			ret = PTR_ERR(st->gain_gpio);
> >> +			dev_err(&spi->dev, "Failed to request gain GPIO: %d\n",
> >> +				ret);
> >> +			goto error_disable_reg;
> >> +		}
> >> +
> >> +		st->filter_gpio = devm_gpiod_get_optional(&spi->dev,
> >> +							  "filter",
> >> +							  GPIOD_OUT_HIGH);
> >> +		if (IS_ERR(st->filter_gpio)) {
> >> +			ret = PTR_ERR(st->filter_gpio);
> >> +			dev_err(&spi->dev,
> >> +				"Failed to request filter GPIO: %d\n",
> >> +				ret);
> >> +			goto error_disable_reg;
> >> +		}
> >> +	}
> >> +
> >>  	ret = ad_sd_setup_buffer_and_trigger(indio_dev);
> >>  	if (ret)
> >>  		goto error_disable_reg;  
> >  


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