Re: [PATCH v4 1/9] staging: iio: ad7780: add gain & filter gpio support

From: Ardelean, Alexandru
Date: Fri Mar 01 2019 - 01:56:28 EST

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On Thu, 2019-02-28 at 11:23 -0300, Renato Lui Geh 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>
> ---
> 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
>
> drivers/staging/iio/adc/ad7780.c | 90 +++++++++++++++++++++++++++++---
> 1 file changed, 84 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/staging/iio/adc/ad7780.c
> b/drivers/staging/iio/adc/ad7780.c
> index c4a85789c2db..87fbcf510d45 100644
> --- a/drivers/staging/iio/adc/ad7780.c
> +++ b/drivers/staging/iio/adc/ad7780.c
> @@ -39,6 +39,12 @@
> #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
> +
> +static const unsigned int ad778x_gain[2] = { 1, 128 };
> +static const unsigned int ad778x_odr_avail[2] = { 10000, 16700 };

ad778x_odr_avail[2] is not used in this patch, so it should probably go
into the next one
(i.e. staging: iio: ad7780: add filter reading to ad778x )

one good way of catching stuff like this is to do interactive rebase and
compile your driver on each patch to see if the compiler catches this;
i suspect the compiler would have thrown an error for this change

>
> struct ad7780_chip_info
> struct iio_chan_spec channel;
> unsigned int pattern_mask;
> @@ -50,7 +56,10 @@ 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;
> };
> @@ -104,17 +113,65 @@ 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;
> + default:
> + break;

The indentation of the break statement is inconsistent with other places.
Still, it does not add much value adding this change as-is, since it does
not change any behavior, and is not an element needed by this change (i.e.
adding gain & filter support via gpios)

> }
>
> 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;
> + 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)
> {
> @@ -126,10 +183,7 @@ 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];

The new `ad778x_gain[]` array could have been it's own patch, but from my
side it's fine to leave it here.
I do like this change, but it's not a patch that semantically has to do
anything with adding gain & filter gpio support.

Let's see what Jonathan says.

> }
>
> return 0;
> @@ -173,6 +227,7 @@ 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 +277,29 @@ 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,
> + "adi,gain",
> + 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,
> + "adi,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;
> + }
> + }
> +

This is just a preference of mine [feel free to ignore for this patch].
But, for this block of code, I would have added a separate function [
called something like ad7780_init_gpios(struct device *dev, struct
ad7780_state *st) )

you could also move the powerdown gpio there; and do something like

static int ad7780_init_gpios(struct device *dev, struct ad7780_state *st)
{

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;
}

/**
* Note Alex: I'm a big fan of keeping things to a minimal
* indentation level [especially where things can be elegant],
* but that's a preference of mine
*/
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;
}

> ret = ad_sd_setup_buffer_and_trigger(indio_dev);
> if (ret)
> goto error_disable_reg;
> --
> 2.21.0
>

Next message: Maya Nakamura: "[PATCH v5 1/3] PCI: hv: Add __aligned(8) to struct retarget_msi_interrupt"
Previous message: Andre Przywara: "Re: [PATCH v5 02/10] arm64: add sysfs vulnerability show for spectre v1"
Next in thread: Dan Carpenter: "Re: [PATCH v4 1/9] staging: iio: ad7780: add gain & filter gpio support"
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