Am 04.03.2017 um 00:53 schrieb Martin Blumenstingl:
> 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.
Indeed ..
> However, Amlogic's Linux driver uses the same "calibration logic" for
> anything pre-GXBB until GXL/GXM, see [1] and [2]
>
Thanks for the links. Then most likely we can do the same.
>> 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?
>
I will send a v2 based on the scaling code.
> 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?
>
I prefer to use GENMASK only if the value is supposed to be
used as an actual mask in a bit operation.
>> +}
>> +
>> 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
>
Finding good variable names is the hardest part in coding ..
Maybe we can do it like in the vendor driver and use nominal/value
instead.
>> +
>> + /* 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
>
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