Hi Heiner,
thanks for this patch!
On Fri, Mar 3, 2017 at 10:13 PM, Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
> The calibration on Meson GXBB is different from the one on GXM/GXL.
I guess you are referring to the "12bit calibration" code from u-boot
[0] which uses MESON_SAR_ADC_REG13_12BIT_CALIBRATION_MASK.
However, Amlogic's Linux driver uses the same "calibration logic" for
anything pre-GXBB until GXL/GXM, see [1] and [2]
> 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.
in early versions of my IIO driver I had "calibration" support
(Amlogic Linux kernel driver style, which uses scaling), see [3]
on my Khadas VIM (GXL) this resulted in values which were basically
identical with the values reported by Amlogic's Linux driver (I can't
remember if I compared this with the u-boot values also).
do you still have a version of your scaling code at hand (if not then
I'll try to hack something up this weekend) so I can give that a try
on a GXL based device?
a few minor nits inline below
> Successfully tested on a Odroid C2. Calibbias is 8 on my system.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> ---
> drivers/iio/adc/meson_saradc.c | 56 ++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> index 23710088..276375c7 100644
> --- a/drivers/iio/adc/meson_saradc.c
> +++ b/drivers/iio/adc/meson_saradc.c
> @@ -173,7 +173,8 @@
> .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), \
> .datasheet_name = "SAR_ADC_CH"#_chan, \
> }
>
> @@ -233,6 +234,7 @@ struct meson_sar_adc_priv {
> struct clk *adc_div_clk;
> struct clk_divider clk_div;
> struct completion done;
> + int calibbias;
> };
>
> static const struct regmap_config meson_sar_adc_regmap_config = {
> @@ -252,6 +254,14 @@ 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);
> +
> + return clamp(val + priv->calibbias, 0,
> + (1 << priv->data->resolution) - 1);
any reason why you're not using GENMASK as your are doing in
meson_sar_adc_read_raw_sample?
> +}
> +
> 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 +313,7 @@ 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 +539,10 @@ 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;
> +
> default:
> return -EINVAL;
> }
> @@ -754,6 +768,38 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data)
> return IRQ_HANDLED;
> }
>
> +static int meson_sar_adc_calib_gxbb(struct iio_dev *indio_dev)
> +{
> + struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> + int ret, act0, act1, set0, set1;
I don't have better names at the moment, but the "act" and "set"
variables sound a bit strange
> +
> + /* use points 25% and 75% for calibration */
> + set0 = (1 << priv->data->resolution) / 4;
> + set1 = (1 << priv->data->resolution) * 3 / 4;
just like I mentioned above: any reason why you're not using GENMASK
here as well?
> +
> + meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_DIV4);
> + ret = meson_sar_adc_get_sample(indio_dev,
> + &meson_sar_adc_iio_channels[7],
> + MEAN_AVERAGING, EIGHT_SAMPLES, &act0);
> + if (ret < 0)
> + goto out;
> +
> + meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_MUL3_DIV4);
> + ret = meson_sar_adc_get_sample(indio_dev,
> + &meson_sar_adc_iio_channels[7],
> + MEAN_AVERAGING, EIGHT_SAMPLES, &act1);
> + if (ret < 0)
> + goto out;
> +
> + priv->calibbias = (set0 + set1 - act0 - act1) / 2;
> +
> + 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 +952,12 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
> if (ret)
> goto err;
>
> + if (priv->data == &meson_sar_adc_gxbb_data) {
> + ret = meson_sar_adc_calib_gxbb(indio_dev);
> + if (ret)
> + goto err_hw;
> + }
> +
> platform_set_drvdata(pdev, indio_dev);
>
> ret = iio_device_register(indio_dev);
> --
> 2.12.0
>
Regards,
Martin
[0] https://github.com/khadas/u-boot/blob/d69d067db45d3002df0ad92558285e4671adb203/drivers/adc/saradc.c#L163
[1] https://github.com/hardkernel/linux/blob/odroidc-3.10.y/drivers/amlogic/input/saradc/saradc.c#L92
[2] https://github.com/khadas/linux/blob/6cb8e8669d2fb051f681f403c89ddf907a229586/drivers/amlogic/input/saradc/saradc.c#L108
[3] https://github.com/xdarklight/linux/blob/9b3887d228b93ac0657ba454a924a45afedc2064/drivers/iio/adc/meson_saradc.c
--
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
