Re: [PATCH v5 3/5] iio: adc: ad7949: add support for internal vref
From: Jonathan Cameron
Date: Sun Aug 08 2021 - 12:33:47 EST
On Sat, 7 Aug 2021 21:56:57 -0400
Liam Beguin <liambeguin@xxxxxxxxx> wrote:
> From: Liam Beguin <lvb@xxxxxxxxxx>
>
> Add support for selecting a custom reference voltage from the
> devicetree. If an external source is used, a vref regulator should be
> defined in the devicetree.
>
> Signed-off-by: Liam Beguin <lvb@xxxxxxxxxx>
Hi Liam, I'm not sure the parsing of the child nodes will work if using
an external reference. See below.
Jonathan
> ---
> drivers/iio/adc/ad7949.c | 140 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 122 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index 3f94ae639a44..14a7c79d637e 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -35,7 +35,11 @@
>
> /* REF: reference/buffer selection */
> #define AD7949_CFG_BIT_REF GENMASK(5, 3)
> -#define AD7949_CFG_VAL_REF_EXT_BUF 7
> +#define AD7949_CFG_VAL_REF_EXT_TEMP_BUF 3
> +#define AD7949_CFG_VAL_REF_EXT_TEMP 2
> +#define AD7949_CFG_VAL_REF_INT_4096 1
> +#define AD7949_CFG_VAL_REF_INT_2500 0
> +#define AD7949_CFG_VAL_REF_EXTERNAL BIT(1)
>
> /* SEQ: channel sequencer. Allows for scanning channels */
> #define AD7949_CFG_BIT_SEQ GENMASK(2, 1)
> @@ -60,6 +64,14 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
> [ID_AD7689] = { .num_channels = 8, .resolution = 16 },
> };
>
> +/**
> + * struct ad7949_channel - ADC Channel parameters
> + * @refsel: reference selection
> + */
> +struct ad7949_channel {
> + u32 refsel;
> +};
> +
> /**
> * struct ad7949_adc_chip - AD ADC chip
> * @lock: protects write sequences
> @@ -78,6 +90,7 @@ struct ad7949_adc_chip {
> struct regulator *vref;
> struct iio_dev *indio_dev;
> struct spi_device *spi;
> + struct ad7949_channel *channels;
> u8 resolution;
> u8 bits_per_word;
> u16 cfg;
> @@ -136,6 +149,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> int ret;
> int i;
> struct spi_message msg;
> + struct ad7949_channel *ad7949_chan = &ad7949_adc->channels[channel];
> struct spi_transfer tx[] = {
> {
> .len = 2,
> @@ -156,8 +170,9 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> */
> for (i = 0; i < 2; i++) {
> ret = ad7949_spi_write_cfg(ad7949_adc,
> - FIELD_PREP(AD7949_CFG_BIT_INX, channel),
> - AD7949_CFG_BIT_INX);
> + FIELD_PREP(AD7949_CFG_BIT_INX, channel) |
> + FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_chan->refsel),
> + AD7949_CFG_BIT_INX | AD7949_CFG_BIT_REF);
> if (ret)
> return ret;
> if (channel == ad7949_adc->current_channel)
> @@ -225,6 +240,7 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
> int *val, int *val2, long mask)
> {
> struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
> + struct ad7949_channel *ad7949_chan = &ad7949_adc->channels[chan->channel];
> int ret;
>
> if (!val)
> @@ -242,12 +258,26 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
> return IIO_VAL_INT;
>
> case IIO_CHAN_INFO_SCALE:
> - ret = regulator_get_voltage(ad7949_adc->vref);
> - if (ret < 0)
> - return ret;
> + switch (ad7949_chan->refsel) {
> + case AD7949_CFG_VAL_REF_INT_2500:
> + *val = 2500;
> + break;
> + case AD7949_CFG_VAL_REF_INT_4096:
> + *val = 4096;
> + break;
> + case AD7949_CFG_VAL_REF_EXT_TEMP:
> + case AD7949_CFG_VAL_REF_EXT_TEMP_BUF:
> + ret = regulator_get_voltage(ad7949_adc->vref);
> + if (ret < 0)
> + return ret;
> +
> + /* convert value back to mV */
> + *val = ret / 1000;
> + break;
> + }
>
> - *val = ret / 5000;
> - return IIO_VAL_INT;
> + *val2 = (1 << ad7949_adc->resolution) - 1;
> + return IIO_VAL_FRACTIONAL;
> }
>
> return -EINVAL;
> @@ -286,7 +316,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
> FIELD_PREP(AD7949_CFG_BIT_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
> FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc->current_channel) |
> FIELD_PREP(AD7949_CFG_BIT_BW_FULL, 1) |
> - FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_CFG_VAL_REF_EXT_BUF) |
> + FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc->channels[0].refsel) |
> FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
> FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
>
> @@ -302,14 +332,24 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
> return ret;
> }
>
> +static void ad7949_disable_reg(void *reg)
> +{
> + regulator_disable(reg);
> +}
> +
> static int ad7949_spi_probe(struct spi_device *spi)
> {
> u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
> struct device *dev = &spi->dev;
> const struct ad7949_adc_spec *spec;
> struct ad7949_adc_chip *ad7949_adc;
> + struct ad7949_channel *ad7949_chan;
> + struct fwnode_handle *child;
> struct iio_dev *indio_dev;
> + int mode;
> + u32 tmp;
> int ret;
> + int i;
>
> indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
> if (!indio_dev) {
> @@ -343,16 +383,82 @@ static int ad7949_spi_probe(struct spi_device *spi)
> return -EINVAL;
> }
>
> - ad7949_adc->vref = devm_regulator_get(dev, "vref");
> + /* Setup external voltage ref, buffered? */
> + ad7949_adc->vref = devm_regulator_get_optional(dev, "vrefin");
> if (IS_ERR(ad7949_adc->vref)) {
> - dev_err(dev, "fail to request regulator\n");
> - return PTR_ERR(ad7949_adc->vref);
> + ret = PTR_ERR(ad7949_adc->vref);
> + if (ret != -ENODEV)
> + return ret;
> + /* unbuffered? */
> + ad7949_adc->vref = devm_regulator_get_optional(dev, "vref");
> + if (IS_ERR(ad7949_adc->vref)) {
> + ret = PTR_ERR(ad7949_adc->vref);
> + if (ret != -ENODEV)
> + return ret;
> + /* Internal then */
> + mode = AD7949_CFG_VAL_REF_INT_4096;
> + } else {
> + mode = AD7949_CFG_VAL_REF_EXT_TEMP;
> + }
> + } else {
> + mode = AD7949_CFG_VAL_REF_EXT_TEMP_BUF;
> }
>
> - ret = regulator_enable(ad7949_adc->vref);
> - if (ret < 0) {
> - dev_err(dev, "fail to enable regulator\n");
> - return ret;
> + if (mode & AD7949_CFG_VAL_REF_EXTERNAL) {
> + ret = regulator_enable(ad7949_adc->vref);
> + if (ret < 0) {
> + dev_err(dev, "fail to enable regulator\n");
> + return ret;
> + }
> +
> + ret = devm_add_action_or_reset(dev, ad7949_disable_reg,
> + ad7949_adc->vref);
> + if (ret)
> + return ret;
> + }
> +
> + ad7949_adc->channels = devm_kcalloc(dev, spec->num_channels,
> + sizeof(*ad7949_adc->channels),
> + GFP_KERNEL);
> + if (!ad7949_adc->channels) {
> + dev_err(dev, "unable to allocate ADC channels\n");
> + return -ENOMEM;
> + }
> +
> + /* Initialize all channel structures */
> + for (i = 0; i < spec->num_channels; i++)
> + ad7949_adc->channels[i].refsel = mode;
> +
> + /* Read channel specific information form the devicetree */
> + device_for_each_child_node(dev, child) {
> + ret = fwnode_property_read_u32(child, "reg", &i);
> + if (ret) {
> + dev_err(dev, "missing reg property in %pfw\n", child);
> + fwnode_handle_put(child);
> + return ret;
> + }
> +
> + ad7949_chan = &ad7949_adc->channels[i];
> +
> + ret = fwnode_property_read_u32(child, "adi,internal-ref-microvolt", &tmp);
> + if (ret < 0 && ret != -EINVAL) {
> + dev_err(dev, "invalid internal reference in %pfw\n", child);
> + fwnode_handle_put(child);
> + return ret;
> + }
So if we are using external voltage, then we'd not expect this to exist.
ret != -EINVAL should deal with that. However, we then hit the following switch
and temp isn't set to an appropriate value so we get the error.
Am I missing something?
> +
> + switch (tmp) {
> + case 2500000:
> + ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_2500;
> + break;
> + case 4096000:
> + ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_4096;
> + break;
> + default:
> + dev_err(dev, "unsupported internal voltage reference\n");
> + fwnode_handle_put(child);
> + return -EINVAL;
> + }
> }
>
> mutex_init(&ad7949_adc->lock);
> @@ -373,7 +479,6 @@ static int ad7949_spi_probe(struct spi_device *spi)
>
> err:
> mutex_destroy(&ad7949_adc->lock);
> - regulator_disable(ad7949_adc->vref);
>
> return ret;
> }
> @@ -385,7 +490,6 @@ static int ad7949_spi_remove(struct spi_device *spi)
>
> iio_device_unregister(indio_dev);
> mutex_destroy(&ad7949_adc->lock);
> - regulator_disable(ad7949_adc->vref);
>
> return 0;
> }