On 24/03/17 22:24, Martin Blumenstingl wrote:
> 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"
Fixed whilst applying.
>>
>> 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>
Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.
Thanks,
Jonathan
>
>> ---
>> 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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