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Date: Sat, 2 Mar 2019 19:03:22 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: "Ardelean, Alexandru" <Alex.Ardelean@...log.com>
Cc: "lars@...afoo.de" <lars@...afoo.de>,
"robh+dt@...nel.org" <robh+dt@...nel.org>,
"Popa, Stefan Serban" <StefanSerban.Popa@...log.com>,
"knaack.h@....de" <knaack.h@....de>,
"Hennerich, Michael" <Michael.Hennerich@...log.com>,
"renatogeh@...il.com" <renatogeh@...il.com>,
"mark.rutland@....com" <mark.rutland@....com>,
"giuliano.belinassi@....br" <giuliano.belinassi@....br>,
"pmeerw@...erw.net" <pmeerw@...erw.net>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
"kernel-usp@...glegroups.com" <kernel-usp@...glegroups.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 1/9] staging: iio: ad7780: add gain & filter gpio
support
On Fri, 1 Mar 2019 06:56:14 +0000
"Ardelean, Alexandru" <Alex.Ardelean@...log.com> wrote:
> 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@...il.com>
> > Signed-off-by: Giuliano Belinassi <giuliano.belinassi@....br>
> > Co-developed-by: Giuliano Belinassi <giuliano.belinassi@....br>
A few follow up comments (particularly as Alex asked questions ;)
> > ---
> > 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)
Agreed. This is a tidy up. Good one, but put it in a series doing just
tidy ups.
>
> > }
> >
> > 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;
Should return an error I think? Any such write isn't valid.
> > +
> > + 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.
It's small enough I don't mind, but ideal would have been a precursor patch
doing that refactoring.
>
> > }
> >
> > 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
> */
Me too ;) Fast exit is always nice as well as saves anyone who cares
about this condition looking further.
> 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
> >
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