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.
Successfully tested on a Odroid C2. Calibbias is 8 on my system.
Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
---
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);
--
2.12.0
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
