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It measures the voltage across an external shunt resistor and the input bus voltage, storing the results in an internal FIFO. Add a direct-mode IIO driver exposing the current and voltage channels with raw, scale and hardware-gain attributes, a configurable oversampling (digital averaging) ratio, and PEC-protected register access. The current scale is derived from the shunt resistor value described in the device tree. The driver operates in single-measurement mode: each raw read triggers an on-demand conversion via SMBus Quick Command and returns a matched current/voltage pair. This avoids the latency and complexity of the continuous FIFO mode while ensuring each read reflects the current state. The two selectable current-sense ranges are exposed through scale/scale_available. Continuous FIFO buffering, threshold events and the alert interrupt are intentionally left out of this initial submission and may be added later. Co-developed-by: Ciprian Hegbeli Signed-off-by: Ciprian Hegbeli Signed-off-by: Stefan Popa Reviewed-by: Siratul Islam --- MAINTAINERS | 1 + drivers/iio/adc/Kconfig | 11 + drivers/iio/adc/Makefile | 1 + drivers/iio/adc/max40080.c | 572 +++++++++++++++++++++++++++++++++++++ 4 files changed, 585 insertions(+) create mode 100644 drivers/iio/adc/max40080.c diff --git a/MAINTAINERS b/MAINTAINERS index c1e5afa42de2e..27f3be3ead889 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -15520,6 +15520,7 @@ L: linux-iio@vger.kernel.org S: Supported W: https://ez.analog.com/linux-software-drivers F: Documentation/devicetree/bindings/iio/adc/adi,max40080.yaml +F: drivers/iio/adc/max40080.c MAXIM MAX7360 KEYPAD LED MFD DRIVER M: Mathieu Dubois-Briand diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig index 58da8255525e4..b651c57bbc3f5 100644 --- a/drivers/iio/adc/Kconfig +++ b/drivers/iio/adc/Kconfig @@ -1041,6 +1041,17 @@ config MAX34408 To compile this driver as a module, choose M here: the module will be called max34408. +config MAX40080 + tristate "Analog Devices MAX40080 Current Sense Amplifier" + depends on I2C + help + Say yes here to build support for the Analog Devices MAX40080 + bidirectional current-sense amplifier with a 12-bit ADC and an I2C + interface. + + To compile this driver as a module, choose M here: the module will be + called max40080. + config MAX77541_ADC tristate "Analog Devices MAX77541 ADC driver" depends on MFD_MAX77541 diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile index 7cc8f9a12f763..e1953353c68a4 100644 --- a/drivers/iio/adc/Makefile +++ b/drivers/iio/adc/Makefile @@ -91,6 +91,7 @@ obj-$(CONFIG_MAX1241) += max1241.o obj-$(CONFIG_MAX1363) += max1363.o obj-$(CONFIG_MAX14001) += max14001.o obj-$(CONFIG_MAX34408) += max34408.o +obj-$(CONFIG_MAX40080) += max40080.o obj-$(CONFIG_MAX77541_ADC) += max77541-adc.o obj-$(CONFIG_MAX9611) += max9611.o obj-$(CONFIG_MCP320X) += mcp320x.o diff --git a/drivers/iio/adc/max40080.c b/drivers/iio/adc/max40080.c new file mode 100644 index 0000000000000..1a6568eabcaa0 --- /dev/null +++ b/drivers/iio/adc/max40080.c @@ -0,0 +1,572 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * MAX40080 Digital Current-Sense Amplifier driver + * + * Copyright 2026 Analog Devices, Inc. + * + * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX40080.pdf + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include + +#define MAX40080_REG_CFG 0x00 +#define MAX40080_CFG_MODE_MSK GENMASK(2, 0) +#define MAX40080_CFG_PEC_EN_MSK BIT(5) +#define MAX40080_CFG_RANGE_MSK BIT(6) +#define MAX40080_CFG_FILTER_MSK GENMASK(14, 12) + +#define MAX40080_REG_FIFO_CFG 0x0A +#define MAX40080_FIFO_CFG_STORE_IV_MSK GENMASK(1, 0) + +#define MAX40080_REG_IV 0x10 +/* Current is a 13-bit two's-complement value (magnitude + sign bit). */ +#define MAX40080_IV_I_MSK GENMASK(12, 0) +#define MAX40080_IV_I_SIGN_BIT 12 +#define MAX40080_IV_V_MAG_MSK GENMASK(27, 16) +#define MAX40080_IV_VALID_MSK BIT(31) + +/* CFG.mode field values. */ +#define MAX40080_CFG_MODE_STDBY 0x00 +#define MAX40080_CFG_MODE_SINGLE 0x02 + +/* CFG.range field values. */ +#define MAX40080_CFG_RANGE_50mV 0 +#define MAX40080_CFG_RANGE_10mV 1 + +/* FIFO_CFG.store_iv field values. */ +#define MAX40080_FIFO_CFG_STORE_IV 0x02 + +#define MAX40080_ADC_RES_BITS 12 +#define MAX40080_INTER_VREF_mV 1250 +#define MAX40080_V_BUFF_GAIN 30 +#define MAX40080_CSA_50mV_GAIN 25 +#define MAX40080_CSA_10mV_GAIN 125 + +/* + * The RANGE field (CFG bit 6) selects one of two current-sense full-scale + * ranges (the MAX40080 supports exactly two: +/-50 mV and +/-10 mV). Indexed + * by the CFG.range field value. + */ +static const int max40080_csa_gain[] = { + [MAX40080_CFG_RANGE_50mV] = MAX40080_CSA_50mV_GAIN, + [MAX40080_CFG_RANGE_10mV] = MAX40080_CSA_10mV_GAIN, +}; + +struct max40080_state { + struct i2c_client *client; + /* Serializes read-modify-write access to the CFG register. */ + struct mutex lock; + u32 shunt_resistor_uOhm; + /* Cached configuration: the selected RANGE index and oversampling ratio. */ + unsigned int range; + int oversampling_ratio; + /* + * Precomputed current scale (mA per code) for each RANGE setting, as + * {integer, nano} pairs for IIO_VAL_INT_PLUS_NANO. The range is + * selected by writing the corresponding scale. + */ + int current_scale[2][2]; +}; + +static const int max40080_oversampling_avail[] = { 1, 8, 16, 32, 64, 128 }; + +static int max40080_update_bits(struct max40080_state *st, u8 reg, + u16 mask, u16 val) +{ + int tmp; + + tmp = i2c_smbus_read_word_data(st->client, reg); + if (tmp < 0) + return tmp; + + tmp = (tmp & ~mask) | (val & mask); + + return i2c_smbus_write_word_data(st->client, reg, tmp); +} + +/* + * In single-measurement mode the device sits idle until it receives an SMBus + * Quick Command, then performs exactly one current and one voltage conversion + * and returns to idle. Triggering on demand this way (rather than running the + * FIFO continuously in active mode) means each read returns a fresh, coherent + * current/voltage pair instead of the oldest queued FIFO entry. + */ +static int max40080_trigger_measurement(struct max40080_state *st) +{ + return i2c_smbus_xfer(st->client->adapter, st->client->addr, + st->client->flags, I2C_SMBUS_WRITE, 0, + I2C_SMBUS_QUICK, NULL); +} + +/* + * A single measurement holds the matched current/voltage pair in one 32-bit + * word (MAX40080_REG_IV). Reading all four bytes in one transaction returns + * both from the same conversion; reading the separate current (0x0C) and + * voltage (0x0E) registers would decorrelate the two channels. + * + * Unlike the word accesses used elsewhere, this is a plain I2C block read: the + * SMBus layer does not append or verify a PEC byte for it even when PEC is + * otherwise enabled for the device, so this transfer is not PEC protected. + */ +static int max40080_read_iv_once(struct max40080_state *st, u32 *iv) +{ + __le32 buf; + int ret; + + ret = i2c_smbus_read_i2c_block_data(st->client, MAX40080_REG_IV, + sizeof(buf), (u8 *)&buf); + if (ret < 0) + return ret; + + *iv = le32_to_cpu(buf); + + return 0; +} + +static int max40080_read_iv(struct max40080_state *st, u32 *iv) +{ + u32 tmp = 0; + int ret, io_ret; + + guard(mutex)(&st->lock); + + ret = max40080_trigger_measurement(st); + if (ret < 0) + return ret; + + /* + * Wait for the conversion to complete by polling the FIFO valid bit + * (or bail out on an I2C error). Polling the device's own status makes + * this independent of the actual conversion time, which varies with the + * oversampling ratio and the bus speed. The timeout is only a safety + * ceiling: the worst case is the maximum 128x averaging on both the + * current and voltage channels at the slowest 15 ksps base rate plus the + * inter-channel switching time, i.e. roughly 20 ms; 50 ms leaves ample + * margin. + */ + ret = read_poll_timeout(max40080_read_iv_once, io_ret, + io_ret || (tmp & MAX40080_IV_VALID_MSK), + 500, 50000, false, st, &tmp); + /* + * Propagate the last-read value even on timeout so the caller can + * inspect it for debugging. + */ + *iv = tmp; + if (ret) + return ret; + + return io_ret; +} + +static int max40080_get_current(struct max40080_state *st, int *val) +{ + u32 iv; + int ret; + + ret = max40080_read_iv(st, &iv); + if (ret) + return ret; + + *val = sign_extend32(FIELD_GET(MAX40080_IV_I_MSK, iv), + MAX40080_IV_I_SIGN_BIT); + + return 0; +} + +static int max40080_get_voltage(struct max40080_state *st, int *val) +{ + u32 iv; + int ret; + + ret = max40080_read_iv(st, &iv); + if (ret) + return ret; + + *val = FIELD_GET(MAX40080_IV_V_MAG_MSK, iv); + + return 0; +} + +static int max40080_set_range(struct max40080_state *st, unsigned int range) +{ + int ret; + + ret = max40080_update_bits(st, MAX40080_REG_CFG, MAX40080_CFG_RANGE_MSK, + FIELD_PREP(MAX40080_CFG_RANGE_MSK, range)); + if (ret) + return ret; + + WRITE_ONCE(st->range, range); + + return 0; +} + +/* + * Precompute the current scale (mA per code) for each RANGE setting as + * {integer, nano} pairs. The shunt drop for a full-scale code is + * Vref[mV] / (BIT(ADC_RES_BITS) * gain) + * and current = Vshunt / Rshunt, so with Rshunt in micro-ohms the scale in + * mA/code is + * Vref[mV] * NANO * MICRO / (BIT(ADC_RES_BITS) * gain * Rshunt[uOhm]) + * expressed as an integer part plus a nano fractional part. + */ +static void max40080_calc_current_scale(struct max40080_state *st) +{ + u64 numerator, denominator; + u32 rem; + + for (unsigned int i = 0; i < ARRAY_SIZE(max40080_csa_gain); i++) { + numerator = (u64)MAX40080_INTER_VREF_mV * NANO * MICRO; + denominator = BIT_ULL(MAX40080_ADC_RES_BITS) * max40080_csa_gain[i] * + st->shunt_resistor_uOhm; + numerator = div64_u64(numerator, denominator); + st->current_scale[i][0] = div_u64_rem(numerator, NANO, &rem); + st->current_scale[i][1] = rem; + } +} + +/* + * max40080_oversampling_avail[] is ordered so that its index is the FILTER + * field value (index 0 = no averaging, index 1 = 8x, ...). Return that index + * for an exact match, or -EINVAL for a value that is not on the list. + */ +static int max40080_oversampling_to_filter(int val) +{ + for (unsigned int i = 0; i < ARRAY_SIZE(max40080_oversampling_avail); i++) { + if (max40080_oversampling_avail[i] == val) + return i; + } + + return -EINVAL; +} + +static int max40080_set_oversampling_ratio(struct max40080_state *st, int val) +{ + int filter; + int ret; + + filter = max40080_oversampling_to_filter(val); + if (filter < 0) + return filter; + + ret = max40080_update_bits(st, MAX40080_REG_CFG, MAX40080_CFG_FILTER_MSK, + FIELD_PREP(MAX40080_CFG_FILTER_MSK, filter)); + if (ret) + return ret; + + st->oversampling_ratio = val; + + return 0; +} + +static int max40080_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int *val, int *val2, long mask) +{ + struct max40080_state *st = iio_priv(indio_dev); + unsigned int range; + int ret; + + switch (mask) { + case IIO_CHAN_INFO_RAW: + if (chan->type == IIO_CURRENT) { + ret = max40080_get_current(st, val); + if (ret) + return ret; + } else if (chan->type == IIO_VOLTAGE) { + ret = max40080_get_voltage(st, val); + if (ret) + return ret; + } + return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: + if (chan->type == IIO_CURRENT) { + /* + * The selectable current-sense range is exposed through + * scale: each RANGE setting has its own precomputed + * mA-per-code value. Userspace picks the range by writing + * the matching scale. + * + * Use READ_ONCE to ensure the compiler reads st->range + * exactly once, so val and val2 come from the same setting + * even if a concurrent write changes st->range. + */ + range = READ_ONCE(st->range); + *val = st->current_scale[range][0]; + *val2 = st->current_scale[range][1]; + return IIO_VAL_INT_PLUS_NANO; + } + /* voltage[mV] = raw * Vref[mV] * buffer_gain / BIT(ADC_RES_BITS) */ + *val = MAX40080_INTER_VREF_mV * MAX40080_V_BUFF_GAIN; + *val2 = MAX40080_ADC_RES_BITS; + return IIO_VAL_FRACTIONAL_LOG2; + case IIO_CHAN_INFO_OVERSAMPLING_RATIO: + *val = st->oversampling_ratio; + return IIO_VAL_INT; + default: + return -EINVAL; + } +} + +static int max40080_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int val, int val2, long mask) +{ + struct max40080_state *st = iio_priv(indio_dev); + + guard(mutex)(&st->lock); + + switch (mask) { + case IIO_CHAN_INFO_SCALE: + /* Only the current channel has a selectable range/scale. */ + if (chan->type != IIO_CURRENT) + return -EINVAL; + + for (unsigned int i = 0; i < ARRAY_SIZE(max40080_csa_gain); i++) { + if (val == st->current_scale[i][0] && + val2 == st->current_scale[i][1]) + return max40080_set_range(st, i); + } + + return -EINVAL; + case IIO_CHAN_INFO_OVERSAMPLING_RATIO: + return max40080_set_oversampling_ratio(st, val); + default: + return -EINVAL; + } +} + +static int max40080_write_raw_get_fmt(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + long mask) +{ + switch (mask) { + case IIO_CHAN_INFO_SCALE: + return IIO_VAL_INT_PLUS_NANO; + default: + return IIO_VAL_INT; + } +} + +static int max40080_read_avail(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + const int **vals, int *type, int *length, + long info) +{ + struct max40080_state *st = iio_priv(indio_dev); + + switch (info) { + case IIO_CHAN_INFO_SCALE: + if (chan->type != IIO_CURRENT) + return -EINVAL; + + *vals = (int *)st->current_scale; + *length = ARRAY_SIZE(max40080_csa_gain) * 2; + *type = IIO_VAL_INT_PLUS_NANO; + return IIO_AVAIL_LIST; + case IIO_CHAN_INFO_OVERSAMPLING_RATIO: + *vals = max40080_oversampling_avail; + *length = ARRAY_SIZE(max40080_oversampling_avail); + *type = IIO_VAL_INT; + return IIO_AVAIL_LIST; + default: + return -EINVAL; + } +} + +static int max40080_reg_access(struct iio_dev *indio_dev, unsigned int reg, + unsigned int write_val, unsigned int *read_val) +{ + struct max40080_state *st = iio_priv(indio_dev); + int val; + + if (read_val) { + val = i2c_smbus_read_word_data(st->client, reg); + if (val < 0) + return val; + + *read_val = val; + + return 0; + } + + return i2c_smbus_write_word_data(st->client, reg, write_val); +} + +static const struct iio_info max40080_info = { + .read_raw = max40080_read_raw, + .write_raw = max40080_write_raw, + .write_raw_get_fmt = max40080_write_raw_get_fmt, + .read_avail = max40080_read_avail, + .debugfs_reg_access = &max40080_reg_access, +}; + +static const struct iio_chan_spec max40080_channels[] = { + { + .type = IIO_CURRENT, + .indexed = 1, + .channel = 0, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE), + .info_mask_separate_available = BIT(IIO_CHAN_INFO_SCALE), + .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), + .info_mask_shared_by_all_available = + BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), + }, + { + .type = IIO_VOLTAGE, + .indexed = 1, + .channel = 0, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE), + .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), + .info_mask_shared_by_all_available = + BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), + }, +}; + +/* + * Configure the device from the cached state. The device powers up in standby + * with PEC enabled (CFG POR = 0x0060), so PEC is kept enabled throughout. + */ +static int max40080_init(struct max40080_state *st) +{ + u16 fifo_cfg, cfg; + int ret, filter; + + filter = max40080_oversampling_to_filter(st->oversampling_ratio); + if (filter < 0) + return filter; + + /* + * Put the device in standby before (re)configuring the FIFO: the FIFO + * configuration register can only be written while the device is not + * converting. + */ + cfg = FIELD_PREP(MAX40080_CFG_MODE_MSK, MAX40080_CFG_MODE_STDBY) | + FIELD_PREP(MAX40080_CFG_PEC_EN_MSK, 1); + ret = i2c_smbus_write_word_data(st->client, MAX40080_REG_CFG, cfg); + if (ret) + return ret; + + /* Store a matched current+voltage pair per conversion. */ + fifo_cfg = FIELD_PREP(MAX40080_FIFO_CFG_STORE_IV_MSK, MAX40080_FIFO_CFG_STORE_IV); + ret = i2c_smbus_write_word_data(st->client, MAX40080_REG_FIFO_CFG, + fifo_cfg); + if (ret) + return ret; + + /* + * Use single-measurement mode: the device stays idle and converts once + * per SMBus Quick Command (see max40080_trigger_measurement()), so each + * read returns a fresh sample rather than a queued FIFO entry. + */ + cfg = FIELD_PREP(MAX40080_CFG_MODE_MSK, MAX40080_CFG_MODE_SINGLE) | + FIELD_PREP(MAX40080_CFG_PEC_EN_MSK, 1) | + FIELD_PREP(MAX40080_CFG_RANGE_MSK, st->range) | + FIELD_PREP(MAX40080_CFG_FILTER_MSK, filter); + + return i2c_smbus_write_word_data(st->client, MAX40080_REG_CFG, cfg); +} + +static int max40080_probe(struct i2c_client *client) +{ + struct device *dev = &client->dev; + const char *propname; + struct iio_dev *indio_dev; + struct max40080_state *st; + int ret; + + /* + * The device powers up with PEC enabled (CFG POR = 0x0060) and rejects + * unprotected transactions, so PEC support is mandatory, along with word + * access, the I2C block read used for the current/voltage pair, and the + * Quick Command used to trigger a conversion. + */ + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WORD_DATA | + I2C_FUNC_SMBUS_I2C_BLOCK | + I2C_FUNC_SMBUS_QUICK | + I2C_FUNC_SMBUS_PEC)) + return -EOPNOTSUPP; + + client->flags |= I2C_CLIENT_PEC; + + indio_dev = devm_iio_device_alloc(dev, sizeof(*st)); + if (!indio_dev) + return -ENOMEM; + + st = iio_priv(indio_dev); + st->client = client; + + ret = devm_mutex_init(dev, &st->lock); + if (ret) + return ret; + + propname = "shunt-resistor-micro-ohms"; + ret = device_property_read_u32(dev, propname, &st->shunt_resistor_uOhm); + if (ret) + return dev_err_probe(dev, ret, "can't read %s\n", propname); + if (!st->shunt_resistor_uOhm) + return dev_err_probe(dev, -EINVAL, "%s must be non-zero\n", propname); + + max40080_calc_current_scale(st); + + /* Defaults: 50 mV range, no averaging. */ + st->range = MAX40080_CFG_RANGE_50mV; + st->oversampling_ratio = 1; + + indio_dev->name = "max40080"; + indio_dev->info = &max40080_info; + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->channels = max40080_channels; + indio_dev->num_channels = ARRAY_SIZE(max40080_channels); + + ret = max40080_init(st); + if (ret) + return ret; + + return devm_iio_device_register(dev, indio_dev); +} + +static const struct i2c_device_id max40080_i2c_ids[] = { + { .name = "max40080" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, max40080_i2c_ids); + +static const struct of_device_id max40080_of_match[] = { + { .compatible = "adi,max40080" }, + { } +}; +MODULE_DEVICE_TABLE(of, max40080_of_match); + +static struct i2c_driver max40080_driver = { + .driver = { + .name = "max40080", + .of_match_table = max40080_of_match, + }, + .probe = max40080_probe, + .id_table = max40080_i2c_ids, +}; +module_i2c_driver(max40080_driver); + +MODULE_AUTHOR("Ciprian Hegbeli "); +MODULE_AUTHOR("Stefan Popa "); +MODULE_DESCRIPTION("Analog Devices MAX40080 current-sense amplifier driver"); +MODULE_LICENSE("GPL"); -- 2.53.0