Re: [PATCH v2 10/10] iio: adc: mcp3911: add support to set PGA

Jonathan Cameron
2022-06-25T12:45:07Z

On Sat, 25 Jun 2022 12:38:53 +0200
Marcus Folkesson <marcus.folkesson@gmail.com> wrote:

> Add support for setting the Programmable Gain Amplifiers by adjust the
> scale value.
>
> Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
A few minor things inline.

Thanks,

Jonathan

> ---
>
> Notes:
> v2:
> - add missing comma
> - Address comments from Andy Shevchenko
>
> drivers/iio/adc/mcp3911.c | 134 +++++++++++++++++++++++++++++++-------
> 1 file changed, 110 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> index a019264e73e3..f0179385485f 100644
> --- a/drivers/iio/adc/mcp3911.c
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -26,6 +26,8 @@
> #define MCP3911_REG_MOD 0x06
> #define MCP3911_REG_PHASE 0x07
> #define MCP3911_REG_GAIN 0x09
> +#define MCP3911_GAIN_MASK(ch) (0x7 << 3*ch)
> +#define MCP3911_GAIN_VAL(ch, val) ((val << 3*ch) & MCP3911_GAIN_MASK(ch))
>
> #define MCP3911_REG_STATUSCOM 0x0a
> #define MCP3911_STATUSCOM_DRHIZ BIT(12)
> @@ -55,8 +57,10 @@
> #define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff)
>
> #define MCP3911_NUM_CHANNELS 2
> +#define MCP3911_NUM_SCALES 6
>
> static const int mcp3911_osr_table[] = {32, 64, 128, 256, 512, 1024, 2048, 4096};
> +static u32 mcp3911_scale_table[MCP3911_NUM_SCALES][2];
>
> struct mcp3911 {
> struct spi_device *spi;
> @@ -65,6 +69,7 @@ struct mcp3911 {
> struct clk *clki;
> u32 dev_addr;
> struct iio_trigger *trig;
> + u32 gain[MCP3911_NUM_CHANNELS];
> struct {
> u32 channels[2];
> s64 ts __aligned(8);
> @@ -113,6 +118,37 @@ static int mcp3911_update(struct mcp3911 *adc, u8 reg, u32 mask,
> return mcp3911_write(adc, reg, val, len);
> }
>
> +static int mcp3911_get_gain(struct mcp3911 *adc, u8 channel, u32 *val)
> +{
> + int ret;
> +
> + ret = mcp3911_read(adc, MCP3911_REG_GAIN, val, 1);
> + if (ret)
> + return ret;
> +
> + *val >>= channel * 3;
> + *val &= GENMASK(2, 0);
> + *val = BIT(*val);
> +
> + return 0;
> +}
> +
> +static int mcp3911_write_raw_get_fmt(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + long mask)
> +{
> + switch (mask) {
> + case IIO_CHAN_INFO_SCALE:
> + return IIO_VAL_INT_PLUS_NANO;
> + case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> + return IIO_VAL_INT;
> + case IIO_CHAN_INFO_PHASE:
> + return IIO_VAL_INT;

Ah. here is what I asked for earlier. Please move it back to the
patches that introduced the other features.

> + default:
> + return IIO_VAL_INT_PLUS_NANO;
> + }
> +}
> +
> static int mcp3911_read_avail(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan,
> const int **vals, int *type, int *length,
> @@ -124,6 +160,11 @@ static int mcp3911_read_avail(struct iio_dev *indio_dev,
> *vals = mcp3911_osr_table;
> *length = ARRAY_SIZE(mcp3911_osr_table);
> return IIO_AVAIL_LIST;
> + case IIO_CHAN_INFO_SCALE:
> + *type = IIO_VAL_INT_PLUS_NANO;
> + *vals = (int *)mcp3911_scale_table;
> + *length = ARRAY_SIZE(mcp3911_scale_table) * 2;
> + return IIO_AVAIL_LIST;
> default:
> return -EINVAL;
> }
> @@ -180,29 +221,9 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
> break;
>
> case IIO_CHAN_INFO_SCALE:
> - if (adc->vref) {
> - ret = regulator_get_voltage(adc->vref);
> - if (ret < 0) {
> - dev_err(indio_dev->dev.parent,
> - "failed to get vref voltage: %d\n",
> - ret);
> - goto out;
> - }
> -
> - *val = ret / 1000;
> - } else {
> - *val = MCP3911_INT_VREF_MV;
> - }
> -
> - /*
> - * For 24bit Conversion
> - * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
> - * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
> - */
> -
> - /* val2 = (2^23 * 1.5) */
> - *val2 = 12582912;
> - ret = IIO_VAL_FRACTIONAL;
> + *val = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][0];
> + *val2 = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][1];
> + ret = IIO_VAL_INT_PLUS_NANO;
> break;
> }
>
> @@ -220,6 +241,18 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
>
> mutex_lock(&adc->lock);
> switch (mask) {
> + case IIO_CHAN_INFO_SCALE:
> + for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
> + if (val == mcp3911_scale_table[i][0] &&
> + val2 == mcp3911_scale_table[i][1]) {
> +
> + adc->gain[channel->channel] = BIT(i);
> + ret = mcp3911_update(adc, MCP3911_REG_GAIN,
> + MCP3911_GAIN_MASK(channel->channel),
> + MCP3911_GAIN_VAL(channel->channel, i), 1);
> + }
> + }
> + break;
> case IIO_CHAN_INFO_OFFSET:
> if (val2 != 0) {
> ret = -EINVAL;
> @@ -264,6 +297,48 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> return ret;
> }
>
> +static int mcp3911_calc_scale_table(struct mcp3911 *adc)
> +{
> + u32 ref = MCP3911_INT_VREF_MV;
> + u32 div;
> + int ret;
> + int tmp0, tmp1;
> + s64 tmp2;
> +
> + if (adc->vref) {
> + ret = regulator_get_voltage(adc->vref);
> + if (ret < 0) {
> + dev_err(&adc->spi->dev,
> + "failed to get vref voltage: %d\n",
> + ret);
> + return ret;
> + }
> +
> + ref = ret / 1000;
> + }
> +
> + /*
> + * For 24bit Conversion
> + * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
> + * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
> + */
> +
> + /* ref = Reference voltage

comment syntax is wrong. Also a bit odd to have two comment
blocks next to each other. Please combine them.

> + * div = (2^23 * 1.5 * gain) = 12582912 * gain
> + */
> + for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
> + div = 12582912 * BIT(i);
> + tmp2 = div_s64((s64)ref * 1000000000LL, div);
> + tmp1 = div;
> + tmp0 = (int)div_s64_rem(tmp2, 1000000000, &tmp1);
> +
> + mcp3911_scale_table[i][0] = 0;
> + mcp3911_scale_table[i][1] = tmp1;
> + }
> +
> + return 0;
> +}
> +
> #define MCP3911_CHAN(idx) { \
> .type = IIO_VOLTAGE, \
> .indexed = 1, \
> @@ -276,8 +351,10 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> BIT(IIO_CHAN_INFO_OFFSET) | \
> BIT(IIO_CHAN_INFO_SCALE), \
> - .info_mask_shared_by_type_available = \
> + .info_mask_shared_by_type_available = \
> BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> + .info_mask_separate_available = \
> + BIT(IIO_CHAN_INFO_SCALE), \
> .scan_type = { \
> .sign = 's', \
> .realbits = 24, \
> @@ -330,6 +407,7 @@ static const struct iio_info mcp3911_info = {
> .read_raw = mcp3911_read_raw,
> .write_raw = mcp3911_write_raw,
> .read_avail = mcp3911_read_avail,
> + .write_raw_get_fmt = mcp3911_write_raw_get_fmt,
> };
>
> static irqreturn_t mcp3911_interrupt(int irq, void *dev_id)
> @@ -460,6 +538,14 @@ static int mcp3911_probe(struct spi_device *spi)
> if (ret)
> goto clk_disable;
>
> + ret = mcp3911_calc_scale_table(adc);
> + if (ret)
> + goto clk_disable;
> +
> + /* Store gain values to better calculate scale values */

Run checkpatch.pl You have spaces here which should be a tab.

> + mcp3911_get_gain(adc, 0, &adc->gain[0]);
> + mcp3911_get_gain(adc, 1, &adc->gain[1]);

We'd normally set something like this to default value rather than
rely on sane state from a previous startup. Either that or rely on reset
(which device has, but I don't think driver supports yet).

> +
> if (device_property_read_bool(&adc->spi->dev, "microchip,data-ready-hiz"))
> ret = mcp3911_update(adc, MCP3911_REG_STATUSCOM, MCP3911_STATUSCOM_DRHIZ,
> 0, 2);