[PATCH 2/2] iio: adc: ti-adc128s052: Add lower resolution devices support

Sukrut Bellary
2025-04-08T13:21:47Z

The adcxx4s communicates with a host processor via an SPI/Microwire Bus
interface. The device family responds with 12-bit data, of which the LSB
bits are transmitted by the lower resolution devices as 0.
The unavailable bits are 0 in LSB.
Shift is calculated per resolution and used in scaling and
raw data read.

Lets reuse the driver to support the family of devices with name
ADC<bb><c>S<sss>, where
* bb is the resolution in number of bits (8, 10, 12)
* c is the number of channels (1, 2, 4, 8)
* sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
and 101 for 1 MSPS)

Complete datasheets are available at TI's website here:
https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf

Tested only with ti-adc102s051 on BegalePlay SBC.
https://www.beagleboard.org/boards/beagleplay

Co-developed-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sukrut Bellary <sbellary@baylibre.com>
---
Changes in v3:
- used be16_to_cpu() for the endian conversion.
- used config index enum while setting up the adc128_config[]

- Link to v2:
https://lore.kernel.org/lkml/20231022031203.632153-1-sukrut.bellary@linux.com/

Changes in v2:
- Arranged of_device_id and spi_device_id in numeric order.
- Used enum to index into adc128_config.
- Reorder adc128_config in alphabetical.
- Include channel resolution information.
- Shift is calculated per resolution and used in scaling and
raw data read.

- Link to v1: https://lore.kernel.org/all/20220701042919.18180-1-nm@ti.com/
---
drivers/iio/adc/ti-adc128s052.c | 149 ++++++++++++++++++++++++--------
1 file changed, 112 insertions(+), 37 deletions(-)

diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
index a456ea78462f..d4b76fd85abd 100644
--- a/drivers/iio/adc/ti-adc128s052.c
+++ b/drivers/iio/adc/ti-adc128s052.c
@@ -7,6 +7,22 @@
* https://www.ti.com/lit/ds/symlink/adc128s052.pdf
* https://www.ti.com/lit/ds/symlink/adc122s021.pdf
* https://www.ti.com/lit/ds/symlink/adc124s021.pdf
+ *
+ * The adcxx4s communicates with a host processor via an SPI/Microwire Bus
+ * interface. This driver supports the whole family of devices with a name
+ * ADC<bb><c>S<sss>, where
+ * bb is the resolution in number of bits (8, 10, 12)
+ * c is the number of channels (1, 2, 4, 8)
+ * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
+ * and 101 for 1 MSPS)
+ *
+ * Complete datasheets are available at TI's website here:
+ * https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf
+ *
+ * 8, 10, and 12 bits converters send 12-bit data with
+ * unavailable bits set to 0 in LSB.
+ * Shift is calculated per resolution and used in scaling and
+ * raw data read.
*/

#include <linux/err.h>
@@ -53,7 +69,7 @@ static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
if (ret < 0)
return ret;

- return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
+ return be16_to_cpu(*((__be16 *)adc->buffer));
}

static int adc128_read_raw(struct iio_dev *indio_dev,
@@ -70,7 +86,8 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
if (ret < 0)
return ret;

- *val = ret;
+ *val = (ret >> channel->scan_type.shift) &
+ GENMASK(channel->scan_type.realbits - 1, 0);
return IIO_VAL_INT;

case IIO_CHAN_INFO_SCALE:
@@ -80,7 +97,7 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
return ret;

*val = ret / 1000;
- *val2 = 12;
+ *val2 = channel->scan_type.realbits;
return IIO_VAL_FRACTIONAL_LOG2;

default:
@@ -89,24 +106,34 @@ static int adc128_read_raw(struct iio_dev *indio_dev,

}

-#define ADC128_VOLTAGE_CHANNEL(num) \
- { \
- .type = IIO_VOLTAGE, \
- .indexed = 1, \
- .channel = (num), \
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
- .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
+#define _ADC128_VOLTAGE_CHANNEL(num, real_bits, store_bits) \
+ { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = (num), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+ .scan_index = (num), \
+ .scan_type = { \
+ .sign = 'u', \
+ .realbits = (real_bits), \
+ .storagebits = (store_bits), \
+ .shift = (12 - real_bits), \
+ }, \
}

-static const struct iio_chan_spec adc128s052_channels[] = {
- ADC128_VOLTAGE_CHANNEL(0),
- ADC128_VOLTAGE_CHANNEL(1),
- ADC128_VOLTAGE_CHANNEL(2),
- ADC128_VOLTAGE_CHANNEL(3),
- ADC128_VOLTAGE_CHANNEL(4),
- ADC128_VOLTAGE_CHANNEL(5),
- ADC128_VOLTAGE_CHANNEL(6),
- ADC128_VOLTAGE_CHANNEL(7),
+#define ADC082_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 8, 16)
+#define ADC102_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 10, 16)
+#define ADC128_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 12, 16)
+
+static const struct iio_chan_spec adc082s021_channels[] = {
+ ADC082_VOLTAGE_CHANNEL(0),
+ ADC082_VOLTAGE_CHANNEL(1),
+};
+
+static const struct iio_chan_spec adc102s021_channels[] = {
+ ADC102_VOLTAGE_CHANNEL(0),
+ ADC102_VOLTAGE_CHANNEL(1),
};

static const struct iio_chan_spec adc122s021_channels[] = {
@@ -121,10 +148,46 @@ static const struct iio_chan_spec adc124s021_channels[] = {
ADC128_VOLTAGE_CHANNEL(3),
};

+static const struct iio_chan_spec adc128s052_channels[] = {
+ ADC128_VOLTAGE_CHANNEL(0),
+ ADC128_VOLTAGE_CHANNEL(1),
+ ADC128_VOLTAGE_CHANNEL(2),
+ ADC128_VOLTAGE_CHANNEL(3),
+ ADC128_VOLTAGE_CHANNEL(4),
+ ADC128_VOLTAGE_CHANNEL(5),
+ ADC128_VOLTAGE_CHANNEL(6),
+ ADC128_VOLTAGE_CHANNEL(7),
+};
+
+enum adc128_configuration_index {
+ ADC128_CONFIG_INDEX_082S,
+ ADC128_CONFIG_INDEX_102S,
+ ADC128_CONFIG_INDEX_122S,
+ ADC128_CONFIG_INDEX_124S,
+ ADC128_CONFIG_INDEX_128S,
+};
+
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) },
+ [ADC128_CONFIG_INDEX_082S] = {
+ .channels = adc082s021_channels,
+ .num_channels = ARRAY_SIZE(adc082s021_channels)
+ },
+ [ADC128_CONFIG_INDEX_102S] = {
+ .channels = adc102s021_channels,
+ .num_channels = ARRAY_SIZE(adc102s021_channels)
+ },
+ [ADC128_CONFIG_INDEX_122S] = {
+ .channels = adc122s021_channels,
+ .num_channels = ARRAY_SIZE(adc122s021_channels)
+ },
+ [ADC128_CONFIG_INDEX_124S] = {
+ .channels = adc124s021_channels,
+ .num_channels = ARRAY_SIZE(adc124s021_channels)
+ },
+ [ADC128_CONFIG_INDEX_128S] = {
+ .channels = adc128s052_channels,
+ .num_channels = ARRAY_SIZE(adc128s052_channels)
+ },
};

static const struct iio_info adc128_info = {
@@ -177,31 +240,43 @@ static int adc128_probe(struct spi_device *spi)
}

static const struct of_device_id adc128_of_match[] = {
- { .compatible = "ti,adc128s052", .data = &adc128_config[0] },
- { .compatible = "ti,adc122s021", .data = &adc128_config[1] },
- { .compatible = "ti,adc122s051", .data = &adc128_config[1] },
- { .compatible = "ti,adc122s101", .data = &adc128_config[1] },
- { .compatible = "ti,adc124s021", .data = &adc128_config[2] },
- { .compatible = "ti,adc124s051", .data = &adc128_config[2] },
- { .compatible = "ti,adc124s101", .data = &adc128_config[2] },
+ { .compatible = "ti,adc082s021", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
+ { .compatible = "ti,adc082s051", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
+ { .compatible = "ti,adc082s101", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
+ { .compatible = "ti,adc102s021", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
+ { .compatible = "ti,adc102s051", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
+ { .compatible = "ti,adc102s101", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
+ { .compatible = "ti,adc122s021", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
+ { .compatible = "ti,adc122s051", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
+ { .compatible = "ti,adc122s101", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
+ { .compatible = "ti,adc124s021", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
+ { .compatible = "ti,adc124s051", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
+ { .compatible = "ti,adc124s101", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
+ { .compatible = "ti,adc128s052", .data = &adc128_config[ADC128_CONFIG_INDEX_128S] },
{ /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, adc128_of_match);

static const struct spi_device_id adc128_id[] = {
- { "adc128s052", (kernel_ulong_t)&adc128_config[0] },
- { "adc122s021", (kernel_ulong_t)&adc128_config[1] },
- { "adc122s051", (kernel_ulong_t)&adc128_config[1] },
- { "adc122s101", (kernel_ulong_t)&adc128_config[1] },
- { "adc124s021", (kernel_ulong_t)&adc128_config[2] },
- { "adc124s051", (kernel_ulong_t)&adc128_config[2] },
- { "adc124s101", (kernel_ulong_t)&adc128_config[2] },
+ { "adc082s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
+ { "adc082s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
+ { "adc082s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
+ { "adc102s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
+ { "adc102s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
+ { "adc102s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
+ { "adc122s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
+ { "adc122s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
+ { "adc122s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
+ { "adc124s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
+ { "adc124s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
+ { "adc124s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
+ { "adc128s052", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_128S] },
{ }
};
MODULE_DEVICE_TABLE(spi, adc128_id);

static const struct acpi_device_id adc128_acpi_match[] = {
- { "AANT1280", (kernel_ulong_t)&adc128_config[2] },
+ { "AANT1280", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
{ }
};
MODULE_DEVICE_TABLE(acpi, adc128_acpi_match);
--
2.34.1