From 48ba7c3c0b37363d9ddca3354ca503ad721e14dc Mon Sep 17 00:00:00 2001 From: Heiner Kallweit Date: Sat, 18 Mar 2017 19:38:19 +0100 Subject: [PATCH] iio: adc: meson-saradc: add calibration This patch adds calibration for the Meson SAR ADC. Points 25% vref and 75% vref are used for calibration. It uses a simple linear calibration function: SCALE * val + BIAS Successfully tested on a Odroid C2. Signed-off-by: Heiner Kallweit Tested-by: Martin Blumenstingl Reviewed-by: Martin Blumenstingl Signed-off-by: Jonathan Cameron --- 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 cde9ca7a01b8..dd4190b50df6 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 #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); -- 2.30.2