iio: adc: ad799x: Implement selecting external reference voltage input on AD7991...

Make use of the AD7991_REF_SEL bit and support using the external
reference voltage if 'vref-supply' is present. Use VCC voltage supply
as reference if no extra reference is supplied.

Signed-off-by: Florian Boor <florian.boor@kernelconcepts.de>
Link: https://lore.kernel.org/r/20210930104249.2924336-1-florian.boor@kernelconcepts.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index 18bf838..220228c 100644 (file)
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -299,7 +299,11 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
                        GENMASK(chan->scan_type.realbits - 1, 0);
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
-               ret = regulator_get_voltage(st->vref);
+               if (st->vref)
+                       ret = regulator_get_voltage(st->vref);
+               else
+                       ret = regulator_get_voltage(st->reg);
+
                if (ret < 0)
                        return ret;
                *val = ret / 1000;
@@ -770,6 +774,7 @@ static int ad799x_probe(struct i2c_client *client,
                                   const struct i2c_device_id *id)
 {
        int ret;
+       int extra_config = 0;
        struct ad799x_state *st;
        struct iio_dev *indio_dev;
        const struct ad799x_chip_info *chip_info =
@@ -797,14 +802,36 @@ static int ad799x_probe(struct i2c_client *client,
        ret = regulator_enable(st->reg);
        if (ret)
                return ret;
-       st->vref = devm_regulator_get(&client->dev, "vref");
+
+       /* check if an external reference is supplied */
+       st->vref = devm_regulator_get_optional(&client->dev, "vref");
+
        if (IS_ERR(st->vref)) {
-               ret = PTR_ERR(st->vref);
-               goto error_disable_reg;
+               if (PTR_ERR(st->vref) == -ENODEV) {
+                       st->vref = NULL;
+                       dev_info(&client->dev, "Using VCC reference voltage\n");
+               } else {
+                       ret = PTR_ERR(st->vref);
+                       goto error_disable_reg;
+               }
+       }
+
+       if (st->vref) {
+               /*
+                * Use external reference voltage if supported by hardware.
+                * This is optional if voltage / regulator present, use VCC otherwise.
+                */
+               if ((st->id == ad7991) || (st->id == ad7995) || (st->id == ad7999)) {
+                       dev_info(&client->dev, "Using external reference voltage\n");
+                       extra_config |= AD7991_REF_SEL;
+                       ret = regulator_enable(st->vref);
+                       if (ret)
+                               goto error_disable_reg;
+               } else {
+                       st->vref = NULL;
+                       dev_warn(&client->dev, "Supplied reference not supported\n");
+               }
        }
-       ret = regulator_enable(st->vref);
-       if (ret)
-               goto error_disable_reg;
 
        st->client = client;
 
@@ -815,7 +842,7 @@ static int ad799x_probe(struct i2c_client *client,
        indio_dev->channels = st->chip_config->channel;
        indio_dev->num_channels = chip_info->num_channels;
 
-       ret = ad799x_update_config(st, st->chip_config->default_config);
+       ret = ad799x_update_config(st, st->chip_config->default_config | extra_config);
        if (ret)
                goto error_disable_vref;
 
@@ -845,7 +872,8 @@ static int ad799x_probe(struct i2c_client *client,
 error_cleanup_ring:
        iio_triggered_buffer_cleanup(indio_dev);
 error_disable_vref:
-       regulator_disable(st->vref);
+       if (st->vref)
+               regulator_disable(st->vref);
 error_disable_reg:
        regulator_disable(st->reg);
 
@@ -860,7 +888,8 @@ static int ad799x_remove(struct i2c_client *client)
        iio_device_unregister(indio_dev);
 
        iio_triggered_buffer_cleanup(indio_dev);
-       regulator_disable(st->vref);
+       if (st->vref)
+               regulator_disable(st->vref);
        regulator_disable(st->reg);
        kfree(st->rx_buf);
 
@@ -872,7 +901,8 @@ static int __maybe_unused ad799x_suspend(struct device *dev)
        struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
        struct ad799x_state *st = iio_priv(indio_dev);
 
-       regulator_disable(st->vref);
+       if (st->vref)
+               regulator_disable(st->vref);
        regulator_disable(st->reg);
 
        return 0;
@@ -889,17 +919,21 @@ static int __maybe_unused ad799x_resume(struct device *dev)
                dev_err(dev, "Unable to enable vcc regulator\n");
                return ret;
        }
-       ret = regulator_enable(st->vref);
-       if (ret) {
-               regulator_disable(st->reg);
-               dev_err(dev, "Unable to enable vref regulator\n");
-               return ret;
+
+       if (st->vref) {
+               ret = regulator_enable(st->vref);
+               if (ret) {
+                       regulator_disable(st->reg);
+                       dev_err(dev, "Unable to enable vref regulator\n");
+                       return ret;
+               }
        }
 
        /* resync config */
        ret = ad799x_update_config(st, st->config);
        if (ret) {
-               regulator_disable(st->vref);
+               if (st->vref)
+                       regulator_disable(st->vref);
                regulator_disable(st->reg);
                return ret;
        }