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Subject[PATCH v3 1/2] iio: adc: ti-ads7924: add Texas Instruments ADS7924 driver
From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

The Texas Instruments ADS7924 is a 4 channels, 12-bit analog to
digital converter (ADC) with an I2C interface.

Datasheet: https://www.ti.com/lit/gpn/ads7924

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
---
MAINTAINERS | 7 +
drivers/iio/adc/Kconfig | 11 +
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ti-ads7924.c | 474 +++++++++++++++++++++++++++++++++++
4 files changed, 493 insertions(+)
create mode 100644 drivers/iio/adc/ti-ads7924.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f61eb221415b..1a22d2124ad5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20774,6 +20774,13 @@ M: Robert Richter <rric@kernel.org>
S: Odd Fixes
F: drivers/gpio/gpio-thunderx.c

+TI ADS7924 ADC DRIVER
+M: Hugo Villeneuve <hvilleneuve@dimonoff.com>
+L: linux-iio@vger.kernel.org
+S: Supported
+F: Documentation/devicetree/bindings/iio/adc/ti,ads7924.yaml
+F: drivers/iio/adc/ti-ads7924.c
+
TI AM437X VPFE DRIVER
M: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
L: linux-media@vger.kernel.org
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 63f80d747cbd..5bf4bf16df80 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1207,6 +1207,17 @@ config TI_ADS1015
This driver can also be built as a module. If so, the module will be
called ti-ads1015.

+config TI_ADS7924
+ tristate "Texas Instruments ADS7924 ADC"
+ depends on I2C
+ select REGMAP_I2C
+ help
+ If you say yes here you get support for Texas Instruments ADS7924
+ 4 channels, 12-bit I2C ADC chip.
+
+ This driver can also be built as a module. If so, the module will be
+ called ti-ads7924.
+
config TI_ADS7950
tristate "Texas Instruments ADS7950 ADC driver"
depends on SPI && GPIOLIB
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 4ef41a7dfac6..6b2a2b4ad9ce 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -107,6 +107,7 @@ obj-$(CONFIG_TI_ADC108S102) += ti-adc108s102.o
obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
+obj-$(CONFIG_TI_ADS7924) += ti-ads7924.o
obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
obj-$(CONFIG_TI_ADS8344) += ti-ads8344.o
obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
diff --git a/drivers/iio/adc/ti-ads7924.c b/drivers/iio/adc/ti-ads7924.c
new file mode 100644
index 000000000000..c24fae4ef8e0
--- /dev/null
+++ b/drivers/iio/adc/ti-ads7924.c
@@ -0,0 +1,474 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IIO driver for Texas Instruments ADS7924 ADC, 12-bit, 4-Channels, I2C
+ *
+ * Author: Hugo Villeneuve <hvilleneuve@dimonoff.com>
+ * Copyright 2022 DimOnOff
+ *
+ * based on iio/adc/ti-ads1015.c
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * Datasheet: https://www.ti.com/lit/gpn/ads7924
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+#define ADS7924_CHANNELS 4
+#define ADS7924_BITS 12
+#define ADS7924_DATA_SHIFT 4
+
+/* Registers. */
+#define ADS7924_MODECNTRL_REG 0x00
+#define ADS7924_INTCNTRL_REG 0x01
+#define ADS7924_DATA0_U_REG 0x02
+#define ADS7924_DATA0_L_REG 0x03
+#define ADS7924_DATA1_U_REG 0x04
+#define ADS7924_DATA1_L_REG 0x05
+#define ADS7924_DATA2_U_REG 0x06
+#define ADS7924_DATA2_L_REG 0x07
+#define ADS7924_DATA3_U_REG 0x08
+#define ADS7924_DATA3_L_REG 0x09
+#define ADS7924_ULR0_REG 0x0A
+#define ADS7924_LLR0_REG 0x0B
+#define ADS7924_ULR1_REG 0x0C
+#define ADS7924_LLR1_REG 0x0D
+#define ADS7924_ULR2_REG 0x0E
+#define ADS7924_LLR2_REG 0x0F
+#define ADS7924_ULR3_REG 0x10
+#define ADS7924_LLR3_REG 0x11
+#define ADS7924_INTCONFIG_REG 0x12
+#define ADS7924_SLPCONFIG_REG 0x13
+#define ADS7924_ACQCONFIG_REG 0x14
+#define ADS7924_PWRCONFIG_REG 0x15
+#define ADS7924_RESET_REG 0x16
+
+/*
+ * Register address INC bit: when set to '1', the register address is
+ * automatically incremented after every register read which allows convenient
+ * reading of multiple registers. Set INC to '0' when reading a single register.
+ */
+#define ADS7924_AUTO_INCREMENT_BIT BIT(7)
+
+#define ADS7924_MODECNTRL_MODE_MASK GENMASK(7, 2)
+
+#define ADS7924_MODECNTRL_SEL_MASK GENMASK(1, 0)
+
+#define ADS7924_CFG_INTPOL_BIT 1
+#define ADS7924_CFG_INTTRIG_BIT 0
+
+#define ADS7924_CFG_INTPOL_MASK BIT(ADS7924_CFG_INTPOL_BIT)
+#define ADS7924_CFG_INTTRIG_MASK BIT(ADS7924_CFG_INTTRIG_BIT)
+
+/* Interrupt pin polarity */
+#define ADS7924_CFG_INTPOL_LOW 0
+#define ADS7924_CFG_INTPOL_HIGH 1
+
+/* Interrupt pin signaling */
+#define ADS7924_CFG_INTTRIG_LEVEL 0
+#define ADS7924_CFG_INTTRIG_EDGE 1
+
+/* Mode control values */
+#define ADS7924_MODECNTRL_IDLE 0x00
+#define ADS7924_MODECNTRL_AWAKE 0x20
+#define ADS7924_MODECNTRL_MANUAL_SINGLE 0x30
+#define ADS7924_MODECNTRL_MANUAL_SCAN 0x32
+#define ADS7924_MODECNTRL_AUTO_SINGLE 0x31
+#define ADS7924_MODECNTRL_AUTO_SCAN 0x33
+#define ADS7924_MODECNTRL_AUTO_SINGLE_SLEEP 0x39
+#define ADS7924_MODECNTRL_AUTO_SCAN_SLEEP 0x3B
+#define ADS7924_MODECNTRL_AUTO_BURST_SLEEP 0x3F
+
+#define ADS7924_ACQTIME_MASK GENMASK(4, 0)
+
+#define ADS7924_PWRUPTIME_MASK GENMASK(4, 0)
+
+/*
+ * The power-up time is allowed to elapse whenever the device has been shutdown
+ * in idle mode. Power-up time can allow external circuits, such as an
+ * operational amplifier, between the MUXOUT and ADCIN pins to turn on.
+ * The nominal time programmed by the PUTIME[4:0] register bits is given by:
+ * t PU = PWRUPTIME[4:0] × 2 μs
+ * If a power-up time is not required, set the bits to '0' to effectively bypass.
+ */
+#define ADS7924_PWRUPTIME_US 0 /* Bypass (0us). */
+
+/*
+ * Acquisition Time according to ACQTIME[4:0] register bits.
+ * The Acquisition Time is given by:
+ * t ACQ = (ACQTIME[4:0] × 2 μs) + 6 μs
+ * Using default value of 0 for ACQTIME[4:0] results in a minimum acquisition
+ * time of 6us.
+ */
+#define ADS7924_ACQTIME_US 6
+
+/* The conversion time is always 4μs and cannot be programmed by the user. */
+#define ADS7924_CONVTIME_US 4
+
+#define ADS7924_TOTAL_CONVTIME_US (ADS7924_PWRUPTIME_US + ADS7924_ACQTIME_US + \
+ ADS7924_CONVTIME_US)
+
+#define ADS7924_V_CHAN(_chan, _addr) { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = _chan, \
+ .address = _addr, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+ .datasheet_name = "AIN"#_chan, \
+}
+
+struct ads7924_data {
+ struct device *dev;
+ struct regmap *regmap;
+ struct regulator *vref_reg;
+
+ /* GPIO descriptor for device hard-reset pin. */
+ struct gpio_desc *reset_gpio;
+
+ /*
+ * Protects ADC ops, e.g: concurrent sysfs/buffered
+ * data reads, configuration updates
+ */
+ struct mutex lock;
+
+ /*
+ * Set to true when the ADC is switched to the continuous-conversion
+ * mode and exits from a power-down state. This flag is used to avoid
+ * getting the stale result from the conversion register.
+ */
+ bool conv_invalid;
+};
+
+static bool ads7924_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ case ADS7924_MODECNTRL_REG:
+ case ADS7924_INTCNTRL_REG:
+ case ADS7924_ULR0_REG:
+ case ADS7924_LLR0_REG:
+ case ADS7924_ULR1_REG:
+ case ADS7924_LLR1_REG:
+ case ADS7924_ULR2_REG:
+ case ADS7924_LLR2_REG:
+ case ADS7924_ULR3_REG:
+ case ADS7924_LLR3_REG:
+ case ADS7924_INTCONFIG_REG:
+ case ADS7924_SLPCONFIG_REG:
+ case ADS7924_ACQCONFIG_REG:
+ case ADS7924_PWRCONFIG_REG:
+ case ADS7924_RESET_REG:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static const struct regmap_config ads7924_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = ADS7924_RESET_REG,
+ .writeable_reg = ads7924_is_writeable_reg,
+};
+
+static const struct iio_chan_spec ads7924_channels[] = {
+ ADS7924_V_CHAN(0, ADS7924_DATA0_U_REG),
+ ADS7924_V_CHAN(1, ADS7924_DATA1_U_REG),
+ ADS7924_V_CHAN(2, ADS7924_DATA2_U_REG),
+ ADS7924_V_CHAN(3, ADS7924_DATA3_U_REG),
+};
+
+static int ads7924_get_adc_result(struct ads7924_data *data,
+ struct iio_chan_spec const *chan, int *val)
+{
+ int ret;
+ __be16 be_val;
+
+ if (chan->channel < 0 || chan->channel >= ADS7924_CHANNELS)
+ return -EINVAL;
+
+ if (data->conv_invalid) {
+ int conv_time;
+
+ conv_time = ADS7924_TOTAL_CONVTIME_US;
+ /* Allow 10% for internal clock inaccuracy. */
+ conv_time += conv_time / 10;
+ usleep_range(conv_time, conv_time + 1);
+ data->conv_invalid = false;
+ }
+
+ ret = regmap_raw_read(data->regmap, ADS7924_AUTO_INCREMENT_BIT |
+ chan->address, &be_val, sizeof(be_val));
+ if (ret)
+ return ret;
+
+ *val = be16_to_cpu(be_val) >> ADS7924_DATA_SHIFT;
+
+ return 0;
+}
+
+static int ads7924_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long mask)
+{
+ int ret, vref_uv;
+ struct ads7924_data *data = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&data->lock);
+ ret = ads7924_get_adc_result(data, chan, val);
+ mutex_unlock(&data->lock);
+ if (ret < 0)
+ return ret;
+
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ vref_uv = regulator_get_voltage(data->vref_reg);
+ if (vref_uv < 0)
+ return -EINVAL;
+
+ *val = vref_uv / 1000; /* Convert reg voltage to mV */
+ *val2 = ADS7924_BITS;
+ return IIO_VAL_FRACTIONAL_LOG2;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info ads7924_info = {
+ .read_raw = ads7924_read_raw,
+};
+
+static int ads7924_get_channels_config(struct i2c_client *client,
+ struct iio_dev *indio_dev)
+{
+ struct ads7924_data *priv = iio_priv(indio_dev);
+ struct device *dev = priv->dev;
+ struct fwnode_handle *node;
+ int num_channels = 0;
+
+ device_for_each_child_node(dev, node) {
+ u32 pval;
+ unsigned int channel;
+
+ if (fwnode_property_read_u32(node, "reg", &pval)) {
+ dev_err(dev, "invalid reg on %pfw\n", node);
+ continue;
+ }
+
+ channel = pval;
+ if (channel >= ADS7924_CHANNELS) {
+ dev_err(dev, "invalid channel index %d on %pfw\n",
+ channel, node);
+ continue;
+ }
+
+ num_channels++;
+ }
+
+ if (num_channels <= 0)
+ return -EINVAL;
+
+ return 0;
+}
+
+static int ads7924_set_conv_mode(struct ads7924_data *data, int mode)
+{
+ int ret;
+ unsigned int mode_field;
+ struct device *dev = data->dev;
+
+ /*
+ * When switching between modes, be sure to first select the Awake mode
+ * and then switch to the desired mode. This procedure ensures the
+ * internal control logic is properly synchronized.
+ */
+ if (mode != ADS7924_MODECNTRL_IDLE) {
+ mode_field = FIELD_PREP(ADS7924_MODECNTRL_MODE_MASK,
+ ADS7924_MODECNTRL_AWAKE);
+
+ ret = regmap_update_bits(data->regmap, ADS7924_MODECNTRL_REG,
+ ADS7924_MODECNTRL_MODE_MASK,
+ mode_field);
+ if (ret) {
+ dev_warn(dev, "failed to set awake mode (%pe)\n",
+ ERR_PTR(ret));
+ return ret;
+ }
+ }
+
+ mode_field = FIELD_PREP(ADS7924_MODECNTRL_MODE_MASK, mode);
+
+ ret = regmap_update_bits(data->regmap, ADS7924_MODECNTRL_REG,
+ ADS7924_MODECNTRL_MODE_MASK, mode_field);
+ if (ret)
+ dev_warn(dev, "failed to set mode %d (%pe)\n", mode,
+ ERR_PTR(ret));
+
+ return ret;
+}
+
+static int ads7924_reset(struct iio_dev *indio_dev)
+{
+ struct ads7924_data *data = iio_priv(indio_dev);
+
+ if (data->reset_gpio) {
+ gpiod_set_value(data->reset_gpio, 1); /* Assert. */
+ /* Educated guess: assert time not specified in datasheet... */
+ mdelay(100);
+ gpiod_set_value(data->reset_gpio, 0); /* Deassert. */
+ return 0;
+ }
+
+ /*
+ * A write of 10101010 to this register will generate a
+ * software reset of the ADS7924.
+ */
+ return regmap_write(data->regmap, ADS7924_RESET_REG, 0b10101010);
+};
+
+static void ads7924_reg_disable(void *data)
+{
+ regulator_disable(data);
+}
+
+static void ads7924_set_idle_mode(void *data)
+{
+ ads7924_set_conv_mode(data, ADS7924_MODECNTRL_IDLE);
+}
+
+static int ads7924_probe(struct i2c_client *client)
+{
+ struct iio_dev *indio_dev;
+ struct ads7924_data *data;
+ struct device *dev = &client->dev;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+ if (!indio_dev)
+ return dev_err_probe(dev, -ENOMEM,
+ "failed to allocate iio device\n");
+
+ data = iio_priv(indio_dev);
+
+ data->dev = dev;
+
+ /* Initialize the reset GPIO as output with an initial value of 0. */
+ data->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+ if (IS_ERR(data->reset_gpio))
+ return dev_err_probe(dev, PTR_ERR(data->reset_gpio),
+ "failed to get request reset GPIO\n");
+
+ mutex_init(&data->lock);
+
+ indio_dev->name = "ads7924";
+ indio_dev->modes = INDIO_DIRECT_MODE;
+
+ indio_dev->channels = ads7924_channels;
+ indio_dev->num_channels = ARRAY_SIZE(ads7924_channels);
+ indio_dev->info = &ads7924_info;
+
+ ret = ads7924_get_channels_config(client, indio_dev);
+ if (ret < 0)
+ return dev_err_probe(dev, ret,
+ "failed to get channels configuration\n");
+
+ data->regmap = devm_regmap_init_i2c(client, &ads7924_regmap_config);
+ if (IS_ERR(data->regmap))
+ return dev_err_probe(dev, PTR_ERR(data->regmap),
+ "failed to init regmap\n");
+
+ data->vref_reg = devm_regulator_get(dev, "vref");
+ if (IS_ERR(data->vref_reg))
+ return dev_err_probe(dev, PTR_ERR(data->vref_reg),
+ "failed to get vref regulator\n");
+
+ ret = regulator_enable(data->vref_reg);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to enable regulator\n");
+
+ ret = devm_add_action_or_reset(dev, ads7924_reg_disable, data->vref_reg);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to add regulator disable action\n");
+
+ ret = ads7924_reset(indio_dev);
+ if (ret < 0)
+ return dev_err_probe(dev, ret,
+ "failed to reset device\n");
+
+ ret = ads7924_set_conv_mode(data, ADS7924_MODECNTRL_AUTO_SCAN);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to set conversion mode\n");
+
+ ret = devm_add_action_or_reset(dev, ads7924_set_idle_mode, data);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to add idle mode action\n");
+
+ /* Use minimum signal acquire time. */
+ ret = regmap_update_bits(data->regmap, ADS7924_ACQCONFIG_REG,
+ ADS7924_ACQTIME_MASK,
+ FIELD_PREP(ADS7924_ACQTIME_MASK, 0));
+ if (ret < 0)
+ return dev_err_probe(dev, ret,
+ "failed to configure signal acquire time\n");
+
+ /* Disable power-up time. */
+ ret = regmap_update_bits(data->regmap, ADS7924_PWRCONFIG_REG,
+ ADS7924_PWRUPTIME_MASK,
+ FIELD_PREP(ADS7924_PWRUPTIME_MASK, 0));
+ if (ret < 0)
+ return dev_err_probe(dev, ret,
+ "failed to configure power-up time\n");
+
+ data->conv_invalid = true;
+
+ ret = devm_iio_device_register(dev, indio_dev);
+ if (ret < 0)
+ return dev_err_probe(dev, ret,
+ "failed to register IIO device\n");
+
+ return 0;
+}
+
+static const struct i2c_device_id ads7924_id[] = {
+ { "ads7924", 0 },
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, ads7924_id);
+
+static const struct of_device_id ads7924_of_match[] = {
+ { .compatible = "ti,ads7924", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, ads7924_of_match);
+
+static struct i2c_driver ads7924_driver = {
+ .driver = {
+ .name = "ads7924",
+ .of_match_table = ads7924_of_match,
+ },
+ .probe_new = ads7924_probe,
+ .id_table = ads7924_id,
+};
+
+module_i2c_driver(ads7924_driver);
+
+MODULE_AUTHOR("Hugo Villeneuve <hvilleneuve@dimonoff.com>");
+MODULE_DESCRIPTION("Texas Instruments ADS7924 ADC I2C driver");
+MODULE_LICENSE("GPL");
--
2.30.2
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