Re: [PATCH v5 3/5] iio: adc: ad7949: add support for internal vref
From: Liam Beguin
Date: Sun Aug 08 2021 - 18:43:20 EST
On Sun Aug 8, 2021 at 12:36 PM EDT, Jonathan Cameron wrote:
> 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;
> > + }
Hi Jonathan,
>
> 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?
You're right that using an external reference, will cause this to fail.
My apologies, I've done a poor job of testing the last two revisions of
this patch. I'll do better.
Since a regulator is also required when we're using an external source,
I'll add a check for that. Something like this:
ret = fwnode_property_read_u32(child, "adi,internal-ref-microvolt", &tmp);
if (ret == -EINVAL && mode & AD7949_CFG_VAL_REF_EXTERNAL) {
continue;
} else if (ret < 0) {
dev_err(dev, "invalid voltage reference in %pfw\n", child);
fwnode_handle_put(child);
return ret;
}
Given that we can now have a different scale for each channel based on
the vref source, should BIT(IIO_CHAN_INFO_SCALE) be moved to
.info_mask_separate in the channel definition?
Thanks,
Liam
>
> > +
> > + 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;
> > }