[PATCH v5 01/11] staging: iio: ad7780: add gain & filter gpio support

[Renato Lui Geh <renatogeh@gmail.com>]

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>
---
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
Changes in v4:
 - Removed useless macro
 - Added default case for switch to suppress warning
 - Removed chunks belonging to filter reading, adding these as a
   patch for itself
Changes in v5:
 - ad778x_odr_avail moved to filter patch
 - Split gain reading to its own patch
 - Init GPIOs in a separate function

 drivers/staging/iio/adc/ad7780.c | 114 ++++++++++++++++++++++++++-----
 1 file changed, 96 insertions(+), 18 deletions(-)

diff --git a/drivers/staging/iio/adc/ad7780.c b/drivers/staging/iio/adc/ad7780.c
index c4a85789c2db..07e5e35c92a3 100644
--- a/drivers/staging/iio/adc/ad7780.c
+++ b/drivers/staging/iio/adc/ad7780.c
@@ -39,6 +39,9 @@
 #define AD7170_PATTERN		(AD7780_PAT0 | AD7170_PAT2)
 #define AD7170_PATTERN_MASK	(AD7780_PAT0 | AD7780_PAT1 | AD7170_PAT2)
 
+#define AD7780_GAIN_MIDPOINT	64
+#define AD7780_FILTER_MIDPOINT	13350
+
 struct ad7780_chip_info {
 	struct iio_chan_spec	channel;
 	unsigned int		pattern_mask;
@@ -50,7 +53,10 @@ 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			int_vref_mv;
 
 	struct ad_sigma_delta sd;
 };
@@ -104,8 +110,10 @@ 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));
@@ -115,6 +123,50 @@ static int ad7780_read_raw(struct iio_dev *indio_dev,
 	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 -EINVAL;
+
+	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;
+		gpiod_set_value(st->filter_gpio, val);
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
 static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta,
 				     unsigned int raw_sample)
 {
@@ -125,13 +177,6 @@ static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta,
 	    ((raw_sample & chip_info->pattern_mask) != chip_info->pattern))
 		return -EIO;
 
-	if (chip_info->is_ad778x) {
-		if (raw_sample & AD7780_GAIN)
-			st->gain = 1;
-		else
-			st->gain = 128;
-	}
-
 	return 0;
 }
 
@@ -173,8 +218,47 @@ 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_init_gpios(struct device *dev, struct ad7780_state *st)
+{
+	int ret;
+
+	st->powerdown_gpio = devm_gpiod_get_optional(dev,
+						     "powerdown",
+						     GPIOD_OUT_LOW);
+	if (IS_ERR(st->powerdown_gpio)) {
+		ret = PTR_ERR(st->powerdown_gpio);
+		dev_err(dev, "Failed to request powerdown GPIO: %d\n", ret);
+		return ret;
+	}
+
+	if (!st->chip_info->is_ad778x)
+		return 0;
+
+
+	st->gain_gpio = devm_gpiod_get_optional(dev,
+						"adi,gain",
+						GPIOD_OUT_HIGH);
+	if (IS_ERR(st->gain_gpio)) {
+		ret = PTR_ERR(st->gain_gpio);
+		dev_err(dev, "Failed to request gain GPIO: %d\n", ret);
+		return ret;
+	}
+
+	st->filter_gpio = devm_gpiod_get_optional(dev,
+						  "adi,filter",
+						  GPIOD_OUT_HIGH);
+	if (IS_ERR(st->filter_gpio)) {
+		ret = PTR_ERR(st->filter_gpio);
+		dev_err(dev, "Failed to request filter GPIO: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int ad7780_probe(struct spi_device *spi)
 {
 	struct ad7780_state *st;
@@ -212,15 +296,9 @@ static int ad7780_probe(struct spi_device *spi)
 	indio_dev->num_channels = 1;
 	indio_dev->info = &ad7780_info;
 
-	st->powerdown_gpio = devm_gpiod_get_optional(&spi->dev,
-						     "powerdown",
-						     GPIOD_OUT_LOW);
-	if (IS_ERR(st->powerdown_gpio)) {
-		ret = PTR_ERR(st->powerdown_gpio);
-		dev_err(&spi->dev, "Failed to request powerdown GPIO: %d\n",
-			ret);
-		goto error_disable_reg;
-	}
+	ret = ad7780_init_gpios(&spi->dev, st);
+	if (ret)
+		goto error_cleanup_buffer_and_trigger;
 
 	ret = ad_sd_setup_buffer_and_trigger(indio_dev);
 	if (ret)
-- 
2.21.0