Hi Heiner,
On Sat, Mar 18, 2017 at 7:38 PM, Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
> This patch adds calibration for the Meson SAR ADC.
> Points 25% vref and 75% vref are used for calibration.
> It usesa simple linear calibration function: SCALE * val + BIAS
nit: should be "It uses a"
>
> Successfully tested on a Odroid C2.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Tested-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
looks good to me, so:
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> ---
> v2:
> - added calibration scale
> v3:
> - added define MILLION
> - don't bail out if calibration fails
> ---
> drivers/iio/adc/meson_saradc.c | 77 ++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 75 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> index cde9ca7a..dd4190b5 100644
> --- a/drivers/iio/adc/meson_saradc.c
> +++ b/drivers/iio/adc/meson_saradc.c
> @@ -166,6 +166,8 @@
>
> #define MESON_SAR_ADC_MAX_FIFO_SIZE 32
> #define MESON_SAR_ADC_TIMEOUT 100 /* ms */
> +/* for use with IIO_VAL_INT_PLUS_MICRO */
> +#define MILLION 1000000
back when the initial driver was reviewed I was asked to prefix all
defines (so they won't clash with defines from other drivers, see [0])
- this is why all defines start with MESON_SAR_ADC_
if Jonathan or Peter think that it's worth renaming this #define then
you could rename it to MESON_SAR_ADC_CALIBSCALE_REF (that's what I
came up with, feel free to choose any other/more suitable name though)
> #define MESON_SAR_ADC_CHAN(_chan) { \
> .type = IIO_VOLTAGE, \
> @@ -173,7 +175,9 @@
> .channel = _chan, \
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> BIT(IIO_CHAN_INFO_AVERAGE_RAW), \
> - .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \
> + BIT(IIO_CHAN_INFO_CALIBBIAS) | \
> + BIT(IIO_CHAN_INFO_CALIBSCALE), \
> .datasheet_name = "SAR_ADC_CH"#_chan, \
> }
>
> @@ -233,6 +237,8 @@ struct meson_sar_adc_priv {
> struct clk *adc_div_clk;
> struct clk_divider clk_div;
> struct completion done;
> + int calibbias;
> + int calibscale;
> };
>
> static const struct regmap_config meson_sar_adc_regmap_config = {
> @@ -252,6 +258,17 @@ static unsigned int meson_sar_adc_get_fifo_count(struct iio_dev *indio_dev)
> return FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
> }
>
> +static int meson_sar_adc_calib_val(struct iio_dev *indio_dev, int val)
> +{
> + struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> + int tmp;
> +
> + /* use val_calib = scale * val_raw + offset calibration function */
> + tmp = div_s64((s64)val * priv->calibscale, MILLION) + priv->calibbias;
> +
> + return clamp(tmp, 0, (1 << priv->data->resolution) - 1);
> +}
> +
> static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
> {
> struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> @@ -302,7 +319,7 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
>
> fifo_val = FIELD_GET(MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK, regval);
> fifo_val &= GENMASK(priv->data->resolution - 1, 0);
> - *val = fifo_val;
> + *val = meson_sar_adc_calib_val(indio_dev, fifo_val);
>
> return 0;
> }
> @@ -527,6 +544,15 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
> *val2 = priv->data->resolution;
> return IIO_VAL_FRACTIONAL_LOG2;
>
> + case IIO_CHAN_INFO_CALIBBIAS:
> + *val = priv->calibbias;
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_CALIBSCALE:
> + *val = priv->calibscale / MILLION;
> + *val2 = priv->calibscale % MILLION;
> + return IIO_VAL_INT_PLUS_MICRO;
> +
> default:
> return -EINVAL;
> }
> @@ -762,6 +788,47 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data)
> return IRQ_HANDLED;
> }
>
> +static int meson_sar_adc_calib(struct iio_dev *indio_dev)
> +{
> + struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> + int ret, nominal0, nominal1, value0, value1;
> +
> + /* use points 25% and 75% for calibration */
> + nominal0 = (1 << priv->data->resolution) / 4;
> + nominal1 = (1 << priv->data->resolution) * 3 / 4;
> +
> + meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_DIV4);
> + usleep_range(10, 20);
> + ret = meson_sar_adc_get_sample(indio_dev,
> + &meson_sar_adc_iio_channels[7],
> + MEAN_AVERAGING, EIGHT_SAMPLES, &value0);
> + if (ret < 0)
> + goto out;
> +
> + meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_MUL3_DIV4);
> + usleep_range(10, 20);
> + ret = meson_sar_adc_get_sample(indio_dev,
> + &meson_sar_adc_iio_channels[7],
> + MEAN_AVERAGING, EIGHT_SAMPLES, &value1);
> + if (ret < 0)
> + goto out;
> +
> + if (value1 <= value0) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + priv->calibscale = div_s64((nominal1 - nominal0) * (s64)MILLION,
> + value1 - value0);
> + priv->calibbias = nominal0 - div_s64((s64)value0 * priv->calibscale,
> + MILLION);
> + ret = 0;
> +out:
> + meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);
> +
> + return ret;
> +}
> +
> static const struct iio_info meson_sar_adc_iio_info = {
> .read_raw = meson_sar_adc_iio_info_read_raw,
> .driver_module = THIS_MODULE,
> @@ -901,6 +968,8 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
> return PTR_ERR(priv->vref);
> }
>
> + priv->calibscale = MILLION;
> +
> ret = meson_sar_adc_init(indio_dev);
> if (ret)
> goto err;
> @@ -909,6 +978,10 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
> if (ret)
> goto err;
>
> + ret = meson_sar_adc_calib(indio_dev);
> + if (ret)
> + dev_warn(&pdev->dev, "calibration failed\n");
> +
> platform_set_drvdata(pdev, indio_dev);
>
> ret = iio_device_register(indio_dev);
> --
> 2.12.0
>
>
Regards,
Martin
[0] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/002009.html
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