Re: [PATCH v3 1/4] staging: iio: ad7780: add gain & filter gpio support

From: Renato Lui Geh
Date: Thu Feb 14 2019 - 15:31:23 EST

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@xxxxxxxxx> 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@xxxxxxxxx>
Signed-off-by: Giuliano Belinassi <giuliano.belinassi@xxxxxx>
Co-developed-by: Giuliano Belinassi <giuliano.belinassi@xxxxxx>
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?

+ 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;