Re: [PATCH v3 2/5] iio: ad7949: Support internal Vref

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Thu, 2019-05-23 at 15:12 +0300, Alexandru Ardelean wrote:
> [External]
> 
> 
> On Mon, May 13, 2019 at 7:16 PM Adam Michaelis
> <adam.michaelis@rockwellcollins.com> wrote:
> > 
> > Adding configurable (via device tree) options to select one of the two
> > external reference voltages (REFIN as default, original implementation)
> > or one of the two internal reference voltages provided by the AD7949
> > part family.
> > 
> 

So, I managed to go through the patches.

I'll propose to re-organize the patches into smaller groups.

Let's take this patch + the device-tree patch (associated with this) into another series.
Adding support for internal Vref seems pretty straightforward to me.

The SPI communication patches seem weird and require more thought/digging on our side as well.

I'll wait for Stefan to add his input as well.

Thanks
Alex


> I would run a ./scripts/checkpatch.pl on this patch (maybe also on the series).
> I would only complain about style-stuff (on this patch), but those
> would also get reported by checkpatch.
> 
> > Signed-off-by: Adam Michaelis <adam.michaelis@rockwellcollins.com>
> > ---
> >         V2:
> >         - Add some defines to reduce use of magic numbers.
> >         V3:
> >         - Add bitfield.h macros throughout.
> >         - Re-think usage of device tree parameter to focus on the
> >         actual reference sources instead of the raw hardware
> >         configuration.
> > ---
> >  drivers/iio/adc/ad7949.c | 138 +++++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 111 insertions(+), 27 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > index c7fe27aa2519..b648b1ab9559 100644
> > --- a/drivers/iio/adc/ad7949.c
> > +++ b/drivers/iio/adc/ad7949.c
> > @@ -11,12 +11,23 @@
> >  #include <linux/module.h>
> >  #include <linux/regulator/consumer.h>
> >  #include <linux/spi/spi.h>
> > -
> > -#define AD7949_MASK_CHANNEL_SEL                GENMASK(9, 7)
> > -#define AD7949_MASK_TOTAL              GENMASK(13, 0)
> > -#define AD7949_OFFSET_CHANNEL_SEL      7
> > -#define AD7949_CFG_READ_BACK           0x1
> > -#define AD7949_CFG_REG_SIZE_BITS       14
> > +#include <linux/of.h>
> > +#include <linux/bitfield.h>
> > +
> > +#define AD7949_CFG_REG_SIZE_BITS           14
> > +#define AD7949_CFG_MASK_TOTAL              GENMASK(13, 0)
> > +#define AD7949_CFG_APPLY                   BIT(13)
> > +#define AD7949_CFG_CHAN_CFG                GENMASK(12, 10)
> > +#define AD7949_CFG_CHAN_CFG_UNIPOLAR_GND   0x7
> > +#define AD7949_CFG_CHAN_SEL                GENMASK(9, 7)
> > +#define AD7949_CFG_BW                      BIT(6)
> > +#define AD7949_CFG_BW_FULL                 1
> > +#define AD7949_CFG_REF_SEL                 GENMASK(5, 3)
> > +#define AD7949_CFG_SEQ                     GENMASK(2, 1)
> > +#define AD7949_CFG_SEQ_DISABLED            0x0
> > +#define AD7949_CFG_READBACK                BIT(0)
> > +#define AD7949_CFG_READBACK_EN             0
> > +#define AD7949_CFG_READBACK_DIS            1
> > 
> >  enum {
> >         ID_AD7949 = 0,
> > @@ -24,6 +35,18 @@ enum {
> >         ID_AD7689,
> >  };
> > 
> > +enum ad7949_ref_sel {
> > +       AD7949_REF_2V5 = 0, /* 2.5V internal ref + temp sensor */
> > +       AD7949_REF_4V0, /* 4.096V internal ref + temp sensor */
> > +       AD7949_REF_EXT_TEMP, /* REF + temp sensor */
> > +       AD7949_REF_EXT_TEMP_BUF, /* REFIN + temp sensor */
> > +       AD7949_REF_RSRV_4,
> > +       AD7949_REF_RSRV_5,
> > +       AD7949_REF_EXT, /* REF, no temp */
> > +       AD7949_REF_EXT_BUF, /* REFIN, no temp */
> > +       AD7949_REF_MAX,
> > +};
> > +
> >  struct ad7949_adc_spec {
> >         u8 num_channels;
> >         u8 resolution;
> > @@ -41,6 +64,7 @@ struct ad7949_adc_spec {
> >   * @vref: regulator generating Vref
> >   * @iio_dev: reference to iio structure
> >   * @spi: reference to spi structure
> > + * @ref_sel: selected reference voltage source
> >   * @resolution: resolution of the chip
> >   * @cfg: copy of the configuration register
> >   * @current_channel: current channel in use
> > @@ -51,6 +75,7 @@ struct ad7949_adc_chip {
> >         struct regulator *vref;
> >         struct iio_dev *indio_dev;
> >         struct spi_device *spi;
> > +       enum ad7949_ref_sel ref_sel;
> >         u8 resolution;
> >         u16 cfg;
> >         unsigned int current_channel;
> > @@ -59,7 +84,7 @@ struct ad7949_adc_chip {
> > 
> >  static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
> >  {
> > -       if (!(ad7949_adc->cfg & AD7949_CFG_READ_BACK))
> > +       if (!(ad7949_adc->cfg & AD7949_CFG_READBACK))
> >                 return true;
> > 
> >         return false;
> > @@ -91,7 +116,7 @@ static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
> >         };
> > 
> >         ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
> > -       ad7949_adc->buffer = ad7949_adc->cfg << shift;
> > +       ad7949_adc->buffer = (ad7949_adc->cfg & AD7949_CFG_MASK_TOTAL) << shift;
> >         spi_message_init_with_transfers(&msg, tx, 1);
> >         ret = spi_sync(ad7949_adc->spi, &msg);
> > 
> > @@ -136,8 +161,8 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> >         };
> > 
> >         ret = ad7949_spi_write_cfg(ad7949_adc,
> > -                                  channel << AD7949_OFFSET_CHANNEL_SEL,
> > -                                  AD7949_MASK_CHANNEL_SEL);
> > +                                  FIELD_PREP(AD7949_CFG_CHAN_SEL, channel),
> > +                                  AD7949_CFG_CHAN_SEL);
> >         if (ret)
> >                 return ret;
> > 
> > @@ -204,11 +229,20 @@ 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;
> > +               if (ad7949_adc->vref) {
> > +                       ret = regulator_get_voltage(ad7949_adc->vref);
> > +                       if (ret < 0)
> > +                               return ret;
> > +
> > +                       *val = ret / 5000;
> > +               } else if (ad7949_adc->ref_sel == AD7949_REF_2V5) {
> > +                       *val = 2500;
> > +               } else if (ad7949_adc->ref_sel == AD7949_REF_4V0) {
> > +                       *val = 4096;
> > +               } else {
> > +                       return -EINVAL;
> > +               }
> > 
> > -               *val = ret / 5000;
> >                 return IIO_VAL_INT;
> >         }
> > 
> > @@ -226,7 +260,8 @@ static int ad7949_spi_reg_access(struct iio_dev *indio_dev,
> >                 *readval = ad7949_adc->cfg;
> >         else
> >                 ret = ad7949_spi_write_cfg(ad7949_adc,
> > -                       writeval & AD7949_MASK_TOTAL, AD7949_MASK_TOTAL);
> > +                       writeval & AD7949_CFG_MASK_TOTAL,
> > +                       AD7949_CFG_MASK_TOTAL);
> > 
> >         return ret;
> >  }
> > @@ -240,10 +275,24 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
> >  {
> >         int ret;
> >         int val;
> > +       u16 adc_config = 0;
> > 
> > -       /* Sequencer disabled, CFG readback disabled, IN0 as default channel */
> >         ad7949_adc->current_channel = 0;
> > -       ret = ad7949_spi_write_cfg(ad7949_adc, 0x3C79, AD7949_MASK_TOTAL);
> > +       ad7949_adc->cfg = 0;
> > +
> > +       adc_config |= FIELD_PREP(AD7949_CFG_APPLY, 1);
> > +       adc_config |= FIELD_PREP(AD7949_CFG_CHAN_CFG,
> > +                       AD7949_CFG_CHAN_CFG_UNIPOLAR_GND);
> > +       adc_config |= FIELD_PREP(AD7949_CFG_CHAN_SEL,
> > +                       ad7949_adc->current_channel);
> > +       adc_config |= FIELD_PREP(AD7949_CFG_BW, AD7949_CFG_BW_FULL);
> > +       adc_config |= FIELD_PREP(AD7949_CFG_REF_SEL, ad7949_adc->ref_sel);
> > +       adc_config |= FIELD_PREP(AD7949_CFG_SEQ, AD7949_CFG_SEQ_DISABLED);
> > +       adc_config |= FIELD_PREP(AD7949_CFG_READBACK, AD7949_CFG_READBACK_DIS);
> > +
> > +       ret = ad7949_spi_write_cfg(ad7949_adc,
> > +                       adc_config,
> > +                       AD7949_CFG_MASK_TOTAL);
> > 
> >         /*
> >          * Do a dummy conversion to apply the first configuration setting.
> > @@ -261,6 +310,7 @@ static int ad7949_spi_probe(struct spi_device *spi)
> >         struct ad7949_adc_chip *ad7949_adc;
> >         struct iio_dev *indio_dev;
> >         int ret;
> > +       u32 temp;
> > 
> >         indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
> >         if (!indio_dev) {
> > @@ -279,21 +329,53 @@ static int ad7949_spi_probe(struct spi_device *spi)
> >         ad7949_adc = iio_priv(indio_dev);
> >         ad7949_adc->indio_dev = indio_dev;
> >         ad7949_adc->spi = spi;
> > +       ad7949_adc->vref = NULL;
> > 
> >         spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
> >         indio_dev->num_channels = spec->num_channels;
> >         ad7949_adc->resolution = spec->resolution;
> > 
> > -       ad7949_adc->vref = devm_regulator_get(dev, "vref");
> > -       if (IS_ERR(ad7949_adc->vref)) {
> > -               dev_err(dev, "fail to request regulator\n");
> > -               return PTR_ERR(ad7949_adc->vref);
> > +       ret = of_property_read_u32(ad7949_adc->indio_dev->dev.of_node,
> > +                       "adi,reference-select",
> > +                       &temp);
> > +       if (ret == 0) {
> > +               switch (temp) {
> > +               case 0:
> > +                       ad7949_adc->ref_sel = AD7949_REF_2V5;
> > +                       break;
> > +               case 1:
> > +                       ad7949_adc->ref_sel = AD7949_REF_4V0;
> > +                       break;
> > +               case 2:
> > +                       ad7949_adc->ref_sel = AD7949_REF_EXT;
> > +                       break;
> > +               case 3:
> > +                       ad7949_adc->ref_sel = AD7949_REF_EXT_BUF;
> > +                       break;
> > +               default:
> > +                       ad7949_adc->ref_sel = AD7949_REF_EXT_BUF;
> > +                       dev_warn(dev,
> > +                               "unknown reference-select value, using REFIN external Vref (3) by default\n");
> > +               }
> > +       } else {
> > +               ad7949_adc->ref_sel = AD7949_REF_EXT_BUF;
> > +               dev_warn(dev, "using external Vref by default\n");
> >         }
> > 
> > -       ret = regulator_enable(ad7949_adc->vref);
> > -       if (ret < 0) {
> > -               dev_err(dev, "fail to enable regulator\n");
> > -               return ret;
> > +       /* Check whether using external Vref */
> > +       if ((ad7949_adc->ref_sel != AD7949_REF_2V5) &&
> > +                       (ad7949_adc->ref_sel != AD7949_REF_4V0)) {
> > +               ad7949_adc->vref = devm_regulator_get(dev, "vref");
> > +               if (IS_ERR(ad7949_adc->vref)) {
> > +                       dev_err(dev, "fail to request regulator\n");
> > +                       return PTR_ERR(ad7949_adc->vref);
> > +               }
> > +
> > +               ret = regulator_enable(ad7949_adc->vref);
> > +               if (ret < 0) {
> > +                       dev_err(dev, "fail to enable regulator\n");
> > +                       return ret;
> > +               }
> >         }
> > 
> >         mutex_init(&ad7949_adc->lock);
> > @@ -314,7 +396,8 @@ static int ad7949_spi_probe(struct spi_device *spi)
> > 
> >  err:
> >         mutex_destroy(&ad7949_adc->lock);
> > -       regulator_disable(ad7949_adc->vref);
> > +       if (ad7949_adc->vref)
> > +               regulator_disable(ad7949_adc->vref);
> > 
> >         return ret;
> >  }
> > @@ -326,7 +409,8 @@ static int ad7949_spi_remove(struct spi_device *spi)
> > 
> >         iio_device_unregister(indio_dev);
> >         mutex_destroy(&ad7949_adc->lock);
> > -       regulator_disable(ad7949_adc->vref);
> > +       if (ad7949_adc->vref)
> > +               regulator_disable(ad7949_adc->vref);
> > 
> >         return 0;
> >  }
> > --
> > 1.9.1
> >