[PATCH v3 6/8] iio: adc: ti-adc128s052: Support ROHM BD79104

Matti Vaittinen
2025-04-07T11:36:54Z

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The ROHM BD79104 ADC has identical SPI communication logic as the
ti-adc128s052. Eg, SPI transfer should be 16 clk cycles, conversion is
started when the CS is pulled low, and channel selection is done by
writing the channel ID after two zero bits. Data is contained in
big-endian format in the last 12 bits.

The BD79104 has two input voltage pins. Data sheet uses terms "vdd" and
"iovdd". The "vdd" is used also as an analog reference voltage. Hence
the driver expects finding these from the device-tree, instead of having
the "vref" only as TI's driver.

NOTE: The TI's data sheet[1] does show that the TI's IC does actually
have two voltage inputs as well. Pins are called Va (analog reference)
and Vd (digital supply pin) - but I keep the existing driver behaviour
for the TI's IC "as is", because I have no HW to test changes, and
because I have no real need to touch it.

NOTE II: The BD79104 requires SPI MODE 3.

NOTE III: I used evaluation board "BD79104FV-EVK-001" made by ROHM. With
this board I had to drop the SPI speed below the 20M which is mentioned
in the data-sheet [2]. This, however, may be a limitation of the EVK
board, not the component itself.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Datasheet: https://www.ti.com/lit/ds/symlink/adc128s052.pdf # [1]
Datasheet: https://fscdn.rohm.com/en/products/databook/datasheet/ic/data_converter/dac/bd79104fv-la-e.pdf # [2]

---
Revision history:
v2 =>
- No changes
v1 => v2:
- Use Datasheet tags in commit message.
---
drivers/iio/adc/Kconfig | 2 +-
drivers/iio/adc/ti-adc128s052.c | 40 +++++++++++++++++++++++++++++----
2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 6529df1a498c..bbad7b3d41bf 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1469,7 +1469,7 @@ config TI_ADC128S052
depends on SPI
help
If you say yes here you get support for Texas Instruments ADC128S052,
- ADC122S021 and ADC124S021 chips.
+ ADC122S021, ADC124S021 and ROHM Semiconductor BD79104 chips.

This driver can also be built as a module. If so, the module will be
called ti-adc128s052.
diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
index fa0099356be7..d4721ad90f2c 100644
--- a/drivers/iio/adc/ti-adc128s052.c
+++ b/drivers/iio/adc/ti-adc128s052.c
@@ -21,6 +21,9 @@
struct adc128_configuration {
const struct iio_chan_spec *channels;
u8 num_channels;
+ const char *refname;
+ int num_other_regulators;
+ const char * const (*other_regulators)[];
};

struct adc128 {
@@ -124,10 +127,28 @@ static const struct iio_chan_spec adc124s021_channels[] = {
ADC128_VOLTAGE_CHANNEL(3),
};

+static const char * const bd79104_regulators[] = { "iovdd" };
+
static const struct adc128_configuration adc128_config[] = {
- { adc128s052_channels, ARRAY_SIZE(adc128s052_channels) },
- { adc122s021_channels, ARRAY_SIZE(adc122s021_channels) },
- { adc124s021_channels, ARRAY_SIZE(adc124s021_channels) },
+ {
+ .channels = adc128s052_channels,
+ .num_channels = ARRAY_SIZE(adc128s052_channels),
+ .refname = "vref",
+ }, {
+ .channels = adc122s021_channels,
+ .num_channels = ARRAY_SIZE(adc122s021_channels),
+ .refname = "vref",
+ }, {
+ .channels = adc124s021_channels,
+ .num_channels = ARRAY_SIZE(adc124s021_channels),
+ .refname = "vref",
+ }, {
+ .channels = adc128s052_channels,
+ .num_channels = ARRAY_SIZE(adc128s052_channels),
+ .refname = "vdd",
+ .other_regulators = &bd79104_regulators,
+ .num_other_regulators = 1,
+ },
};

static const struct iio_info adc128_info = {
@@ -162,7 +183,7 @@ static int adc128_probe(struct spi_device *spi)
indio_dev->channels = config->channels;
indio_dev->num_channels = config->num_channels;

- adc->reg = devm_regulator_get(&spi->dev, "vref");
+ adc->reg = devm_regulator_get(&spi->dev, config->refname);
if (IS_ERR(adc->reg))
return PTR_ERR(adc->reg);

@@ -174,6 +195,15 @@ static int adc128_probe(struct spi_device *spi)
if (ret)
return ret;

+ if (config->num_other_regulators) {
+ ret = devm_regulator_bulk_get_enable(&spi->dev,
+ config->num_other_regulators,
+ *config->other_regulators);
+ if (ret)
+ return dev_err_probe(&spi->dev, ret,
+ "Failed to enable regulators\n");
+ }
+
ret = devm_mutex_init(&spi->dev, &adc->lock);
if (ret)
return ret;
@@ -189,6 +219,7 @@ static const struct of_device_id adc128_of_match[] = {
{ .compatible = "ti,adc124s021", .data = &adc128_config[2] },
{ .compatible = "ti,adc124s051", .data = &adc128_config[2] },
{ .compatible = "ti,adc124s101", .data = &adc128_config[2] },
+ { .compatible = "rohm,bd79104", .data = &adc128_config[3] },
{ }
};
MODULE_DEVICE_TABLE(of, adc128_of_match);
@@ -201,6 +232,7 @@ static const struct spi_device_id adc128_id[] = {
{ "adc124s021", (kernel_ulong_t)&adc128_config[2] },
{ "adc124s051", (kernel_ulong_t)&adc128_config[2] },
{ "adc124s101", (kernel_ulong_t)&adc128_config[2] },
+ { "bd79104", (kernel_ulong_t)&adc128_config[3] },
{ }
};
MODULE_DEVICE_TABLE(spi, adc128_id);