Re: [PATCH v2] iio: adc: meson-saradc: add calibration for meson gxbb

[Heiner Kallweit <hkallweit1@gmail.com>]

Am 05.03.2017 um 13:08 schrieb Jonathan Cameron:
> On 04/03/17 16:29, Heiner Kallweit wrote:
>> The calibration on Meson GXBB is different from the one on GXM/GXL.
>> This patch only supports GXBB as I don't have other spec and test hw.
>> Points 25% vref and 75% vref are used for calibration.
>>
>> Adding a calibration scale resulted in no improvement, therefore
>> only a simple calibration bias is supported.
> You probably want to update this description ;)

Uups, yes .. Will wait for Martin's feedback and send a v3 with
at least a updated commit message.

>>
>> Successfully tested on a Odroid C2.  Calibbias is 8 on my system.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>> ---
> Looks good to me.  Will want Martin's Ack on this, so I'll wait for that
> before applying.
> 
> Jonathan
>> v2:
>> - added calibration scale
>> ---
>>  drivers/iio/adc/meson_saradc.c | 74 ++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 72 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
>> index 23710088..d5aa0d04 100644
>> --- a/drivers/iio/adc/meson_saradc.c
>> +++ b/drivers/iio/adc/meson_saradc.c
>> @@ -173,7 +173,9 @@
>>  	.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 +235,8 @@ 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 +256,16 @@ 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;
>> +
>> +	tmp = div_s64((s64)val * priv->calibscale, 1000000) + 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);
>> @@ -303,7 +317,7 @@ 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;
>>  }
>> @@ -529,6 +543,15 @@ 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 / 1000000;
>> +		*val2 = priv->calibscale % 1000000;
>> +		return IIO_VAL_INT_PLUS_MICRO;
>> +
>>  	default:
>>  		return -EINVAL;
>>  	}
>> @@ -754,6 +777,47 @@ 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) * 1000000LL,
>> +				   value1 - value0);
>> +	priv->calibbias = nominal0 - div_s64((s64)value0 * priv->calibscale,
>> +					     1000000);
>> +	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,
>> @@ -893,6 +957,8 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
>>  		return PTR_ERR(priv->vref);
>>  	}
>>  
>> +	priv->calibscale = 1000000;
>> +
>>  	ret = meson_sar_adc_init(indio_dev);
>>  	if (ret)
>>  		goto err;
>> @@ -901,6 +967,10 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
>>  	if (ret)
>>  		goto err;
>>  
>> +	ret = meson_sar_adc_calib(indio_dev);
>> +	if (ret)
>> +		goto err_hw;
>> +
>>  	platform_set_drvdata(pdev, indio_dev);
>>  
>>  	ret = iio_device_register(indio_dev);
>>
> 
>