From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from saturn.retrosnub.co.uk ([178.18.118.26]:48149 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751181AbdCSKIQ (ORCPT ); Sun, 19 Mar 2017 06:08:16 -0400 Subject: Re: [PATCH v3] iio: adc: meson-saradc: add calibration To: Heiner Kallweit , Martin Blumenstingl References: Cc: linux-iio@vger.kernel.org From: Jonathan Cameron Message-ID: Date: Sun, 19 Mar 2017 10:08:14 +0000 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 18/03/17 18:38, Heiner Kallweit 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 > > Successfully tested on a Odroid C2. > > Signed-off-by: Heiner Kallweit > Tested-by: Martin Blumenstingl Looks good to me. I'll leave it a while to let Martin have an opportunity for one last look and perhaps a reviewed-by tag to supplement the tested-by. Give me a poke in a week or so if I seem to have forgotten this! 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 > > #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); >