[PATCH 1/2] hwmon: ina238: add support for samples and update_interval
From: Ferdinand Schwenk via B4 Relay
Date: Fri May 22 2026 - 03:03:56 EST
From: Ferdinand Schwenk <ferdinand.schwenk@xxxxxxxxxxxxx>
The INA238 ADC_CONFIG register (address 0x1) exposes three conversion
time fields (VBUSCT, VSHCT, VTCT) and an averaging count field (AVG)
that allow tuning measurement bandwidth and noise rejection. Expose
these as the standard hwmon chip-level attributes:
chip/samples - R/W averaging count (1, 4, 16, 64, 128, 256,
512, 1024)
chip/update_interval - R/W total conversion cycle time in ms
Reading update_interval returns the sum of the current VBUSCT, VSHCT
and VTCT conversion times. Writing it distributes the desired period
equally across all three fields by selecting the closest supported
conversion time for each, taking the current averaging count into
account.
The SQ52206 (Silergy) uses the same register layout but different
absolute conversion time values (e.g. 66 us instead of 50 us at
index 0). A per-chip conversion-time lookup table is introduced in
struct ina238_config so that the same read/write helpers work
correctly for all variants: ina228, ina237, ina238, ina700, ina780
(all using ina238_conv_time[]) and sq52206 (sq52206_conv_time[]).
The ADC_CONFIG register value is cached in struct ina238_data
(adc_config) so that read-modify-write updates can be performed
without an extra register read on every write.
Signed-off-by: Ferdinand Schwenk <ferdinand.schwenk@xxxxxxxxxxxxx>
---
drivers/hwmon/ina238.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 129 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/ina238.c b/drivers/hwmon/ina238.c
index ff67b03189f7..7bc18e5445b2 100644
--- a/drivers/hwmon/ina238.c
+++ b/drivers/hwmon/ina238.c
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/of.h>
#include <linux/regmap.h>
+#include <linux/util_macros.h>
/* INA238 register definitions */
#define INA238_CONFIG 0x0
@@ -49,6 +50,17 @@
#define INA238_DIAG_ALERT_BUSUL BIT(3)
#define INA238_DIAG_ALERT_POL BIT(2)
+/* INA238_ADC_CONFIG register field masks and shifts */
+#define INA238_ADC_CONFIG_MODE_MASK GENMASK(15, 12)
+#define INA238_ADC_CONFIG_VBUSCT_SHIFT 9
+#define INA238_ADC_CONFIG_VBUSCT_MASK GENMASK(11, 9)
+#define INA238_ADC_CONFIG_VSHCT_SHIFT 6
+#define INA238_ADC_CONFIG_VSHCT_MASK GENMASK(8, 6)
+#define INA238_ADC_CONFIG_VTCT_SHIFT 3
+#define INA238_ADC_CONFIG_VTCT_MASK GENMASK(5, 3)
+#define INA238_ADC_CONFIG_AVG_SHIFT 0
+#define INA238_ADC_CONFIG_AVG_MASK GENMASK(2, 0)
+
#define INA238_REGISTERS 0x20
#define INA238_RSHUNT_DEFAULT 2500 /* uOhm */
@@ -101,6 +113,21 @@ static const struct regmap_config ina238_regmap_config = {
.val_bits = 16,
};
+/* Lookup table for conversion times in usec for INA238 family */
+static const u16 ina238_conv_time[] = {
+ 50, 84, 150, 280, 540, 1052, 2074, 4120,
+};
+
+/* Lookup table for conversion times in usec for SQ52206 */
+static const u16 sq52206_conv_time[] = {
+ 66, 118, 310, 566, 1070, 2090, 4140, 8230,
+};
+
+/* Lookup table for number of samples used in averaging mode */
+static const int ina238_avg_samples[] = {
+ 1, 4, 16, 64, 128, 256, 512, 1024,
+};
+
enum ina238_ids { ina228, ina237, ina238, ina700, ina780, sq52206 };
struct ina238_config {
@@ -112,6 +139,7 @@ struct ina238_config {
u32 power_calculate_factor; /* fixed parameter for power calculation, from datasheet */
u32 bus_voltage_lsb; /* bus voltage LSB, in nV */
int current_lsb; /* current LSB, in uA */
+ const u16 *conv_time; /* conversion time lookup table */
};
struct ina238_data {
@@ -124,6 +152,7 @@ struct ina238_data {
int current_lsb; /* current LSB, in uA */
int power_lsb; /* power LSB, in uW */
int energy_lsb; /* energy LSB, in uJ */
+ u16 adc_config; /* cached ADC_CONFIG register value */
};
static const struct ina238_config ina238_config[] = {
@@ -135,6 +164,7 @@ static const struct ina238_config ina238_config[] = {
.config_default = INA238_CONFIG_DEFAULT,
.bus_voltage_lsb = INA238_BUS_VOLTAGE_LSB,
.temp_resolution = 16,
+ .conv_time = ina238_conv_time,
},
[ina237] = {
.has_20bit_voltage_current = false,
@@ -144,6 +174,7 @@ static const struct ina238_config ina238_config[] = {
.config_default = INA238_CONFIG_DEFAULT,
.bus_voltage_lsb = INA238_BUS_VOLTAGE_LSB,
.temp_resolution = 12,
+ .conv_time = ina238_conv_time,
},
[ina238] = {
.has_20bit_voltage_current = false,
@@ -153,6 +184,7 @@ static const struct ina238_config ina238_config[] = {
.config_default = INA238_CONFIG_DEFAULT,
.bus_voltage_lsb = INA238_BUS_VOLTAGE_LSB,
.temp_resolution = 12,
+ .conv_time = ina238_conv_time,
},
[ina700] = {
.has_20bit_voltage_current = false,
@@ -163,6 +195,7 @@ static const struct ina238_config ina238_config[] = {
.bus_voltage_lsb = INA238_BUS_VOLTAGE_LSB,
.temp_resolution = 12,
.current_lsb = 480,
+ .conv_time = ina238_conv_time,
},
[ina780] = {
.has_20bit_voltage_current = false,
@@ -173,6 +206,7 @@ static const struct ina238_config ina238_config[] = {
.bus_voltage_lsb = INA238_BUS_VOLTAGE_LSB,
.temp_resolution = 12,
.current_lsb = 2400,
+ .conv_time = ina238_conv_time,
},
[sq52206] = {
.has_20bit_voltage_current = false,
@@ -182,6 +216,7 @@ static const struct ina238_config ina238_config[] = {
.config_default = SQ52206_CONFIG_DEFAULT,
.bus_voltage_lsb = SQ52206_BUS_VOLTAGE_LSB,
.temp_resolution = 16,
+ .conv_time = sq52206_conv_time,
},
};
@@ -261,6 +296,83 @@ static int ina228_read_voltage(struct ina238_data *data, int channel, long *val)
return 0;
}
+/* Converting ADC_CONFIG register value to update_interval in usec */
+static inline u32 ina238_reg_to_interval_us(struct ina238_data *data)
+{
+ const u16 *ct = data->config->conv_time;
+ u32 vbusct = ct[(data->adc_config & INA238_ADC_CONFIG_VBUSCT_MASK) >>
+ INA238_ADC_CONFIG_VBUSCT_SHIFT];
+ u32 vshct = ct[(data->adc_config & INA238_ADC_CONFIG_VSHCT_MASK) >>
+ INA238_ADC_CONFIG_VSHCT_SHIFT];
+ u32 vtct = ct[(data->adc_config & INA238_ADC_CONFIG_VTCT_MASK) >>
+ INA238_ADC_CONFIG_VTCT_SHIFT];
+
+ return vbusct + vshct + vtct;
+}
+
+/* Converting update_interval in msec to a single conversion time in usec */
+static inline u32 ina238_interval_ms_to_conv_time(long interval)
+{
+ /* 3 equal conversion times (VBUSCT, VSHCT, VTCT) cover all measurement types */
+ return DIV_ROUND_CLOSEST(interval * 1000, 3);
+}
+
+static int ina238_read_chip(struct device *dev, u32 attr, long *val)
+{
+ struct ina238_data *data = dev_get_drvdata(dev);
+
+ switch (attr) {
+ case hwmon_chip_samples:
+ *val = ina238_avg_samples[(data->adc_config & INA238_ADC_CONFIG_AVG_MASK) >>
+ INA238_ADC_CONFIG_AVG_SHIFT];
+ return 0;
+ case hwmon_chip_update_interval:
+ /* Return in msec */
+ *val = DIV_ROUND_CLOSEST(ina238_reg_to_interval_us(data), 1000);
+ return 0;
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
+static int ina238_write_chip(struct device *dev, u32 attr, long val)
+{
+ struct ina238_data *data = dev_get_drvdata(dev);
+ u16 adc_config;
+ int idx, ret;
+
+ switch (attr) {
+ case hwmon_chip_samples:
+ idx = find_closest(val, ina238_avg_samples,
+ ARRAY_SIZE(ina238_avg_samples));
+ adc_config = (data->adc_config & ~INA238_ADC_CONFIG_AVG_MASK) |
+ (idx << INA238_ADC_CONFIG_AVG_SHIFT);
+ ret = regmap_write(data->regmap, INA238_ADC_CONFIG, adc_config);
+ if (ret)
+ return ret;
+ data->adc_config = adc_config;
+ return 0;
+ case hwmon_chip_update_interval:
+ val = ina238_interval_ms_to_conv_time(val);
+ idx = find_closest(val, data->config->conv_time,
+ ARRAY_SIZE(ina238_conv_time));
+ adc_config = (data->adc_config &
+ ~(INA238_ADC_CONFIG_VBUSCT_MASK |
+ INA238_ADC_CONFIG_VSHCT_MASK |
+ INA238_ADC_CONFIG_VTCT_MASK)) |
+ ((u16)idx << INA238_ADC_CONFIG_VBUSCT_SHIFT) |
+ ((u16)idx << INA238_ADC_CONFIG_VSHCT_SHIFT) |
+ ((u16)idx << INA238_ADC_CONFIG_VTCT_SHIFT);
+ ret = regmap_write(data->regmap, INA238_ADC_CONFIG, adc_config);
+ if (ret)
+ return ret;
+ data->adc_config = adc_config;
+ return 0;
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
static int ina238_read_in(struct device *dev, u32 attr, int channel,
long *val)
{
@@ -587,6 +699,8 @@ static int ina238_read(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long *val)
{
switch (type) {
+ case hwmon_chip:
+ return ina238_read_chip(dev, attr, val);
case hwmon_in:
return ina238_read_in(dev, attr, channel, val);
case hwmon_curr:
@@ -607,6 +721,8 @@ static int ina238_write(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long val)
{
switch (type) {
+ case hwmon_chip:
+ return ina238_write_chip(dev, attr, val);
case hwmon_in:
return ina238_write_in(dev, attr, channel, val);
case hwmon_curr:
@@ -629,6 +745,14 @@ static umode_t ina238_is_visible(const void *drvdata,
bool has_energy = data->config->has_energy;
switch (type) {
+ case hwmon_chip:
+ switch (attr) {
+ case hwmon_chip_samples:
+ case hwmon_chip_update_interval:
+ return 0644;
+ default:
+ return 0;
+ }
case hwmon_in:
switch (attr) {
case hwmon_in_input:
@@ -692,6 +816,9 @@ static umode_t ina238_is_visible(const void *drvdata,
HWMON_I_MIN | HWMON_I_MIN_ALARM)
static const struct hwmon_channel_info * const ina238_info[] = {
+ HWMON_CHANNEL_INFO(chip,
+ HWMON_C_SAMPLES,
+ HWMON_C_UPDATE_INTERVAL),
HWMON_CHANNEL_INFO(in,
/* 0: shunt voltage */
INA238_HWMON_IN_CONFIG,
@@ -798,8 +925,8 @@ static int ina238_probe(struct i2c_client *client)
}
/* Setup ADC_CONFIG register */
- ret = regmap_write(data->regmap, INA238_ADC_CONFIG,
- INA238_ADC_CONFIG_DEFAULT);
+ data->adc_config = INA238_ADC_CONFIG_DEFAULT;
+ ret = regmap_write(data->regmap, INA238_ADC_CONFIG, data->adc_config);
if (ret < 0) {
dev_err(dev, "error configuring the device: %d\n", ret);
return -ENODEV;
--
2.54.0