From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from saturn.retrosnub.co.uk ([178.18.118.26]:42615 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979AbdCYO5j (ORCPT ); Sat, 25 Mar 2017 10:57:39 -0400 Subject: Re: [PATCH v3] iio: adc: meson-saradc: add calibration To: Martin Blumenstingl , Heiner Kallweit References: Cc: linux-iio@vger.kernel.org, pmeerw@pmeerw.net From: Jonathan Cameron Message-ID: Date: Sat, 25 Mar 2017 14:57:09 +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 24/03/17 22:24, Martin Blumenstingl wrote: > Hi Heiner, > > On Sat, Mar 18, 2017 at 7:38 PM, 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 > nit: should be "It uses a" Fixed whilst applying. >> >> Successfully tested on a Odroid C2. >> >> Signed-off-by: Heiner Kallweit >> Tested-by: Martin Blumenstingl > looks good to me, so: > > Reviewed-by: Martin Blumenstingl 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 >