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Date:   Sat, 9 Feb 2019 16:25:06 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Renato Lui Geh <renatogeh@gmail.com>
Cc:     lars@metafoo.de, Michael.Hennerich@analog.com, knaack.h@gmx.de,
        pmeerw@pmeerw.net, gregkh@linuxfoundation.org,
        stefan.popa@analog.com, alexandru.Ardelean@analog.com,
        giuliano.belinassi@usp.br, linux-iio@vger.kernel.org,
        devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
        kernel-usp@googlegroups.com
Subject: Re: [PATCH v3 1/4] staging: iio: ad7780: add gain & filter gpio
 support
Message-ID: <20190209162506.0e790885@archlinux>
In-Reply-To: <786543cbd8d60776083bcaca66f83502f23f561b.1549385784.git.renatogeh@gmail.com>
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        <786543cbd8d60776083bcaca66f83502f23f561b.1549385784.git.renatogeh@gmail.com>
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On Tue, 5 Feb 2019 15:13:00 -0200
Renato Lui Geh <renatogeh@gmail.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@gmail.com>
> Signed-off-by: Giuliano Belinassi <giuliano.belinassi@usp.br>
> Co-developed-by: Giuliano Belinassi <giuliano.belinassi@usp.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?

> +
> +#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.

> +							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;