Re: [PATCH v2 2/2] iio: adc: add driver for Texas Instruments TLA2528 adc

From: Matti Vaittinen

Date: Mon Nov 02 2026 - 02:26:38 EST

On 30/10/2026 18:47, Maxime Chevallier wrote:

Add a new driver for the TI TLA2528 ADC chip. It has 8 12-bit
channels, that can also be configured as 16-bit averaging channels.

This is a very simple driver, allowing reading raw values for each
channel. GPIO mode isn't supported for now, as well as buffered mode and
the 16-bit averaging mode.

Co-developed-by: Rodolfo Giometti <giometti@xxxxxxxxxxxx>
Signed-off-by: Rodolfo Giometti <giometti@xxxxxxxxxxxx>
Signed-off-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>

Looks very nice and clean to me. I made couple of remarks below but they are very minor and I do not require them to be addressed. Nice job!

Reviewed-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>

---
MAINTAINERS | 1 +
drivers/iio/adc/Kconfig | 12 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ti-tla2528.c | 245 +++++++++++++++++++++++++++++++++++
4 files changed, 259 insertions(+)
create mode 100644 drivers/iio/adc/ti-tla2528.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 471585b29c19..1ebb6418ab1f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27720,6 +27720,7 @@ M: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
L: linux-iio@xxxxxxxxxxxxxxx
S: Supported
F: Documentation/devicetree/bindings/iio/adc/ti,tla2528.yaml
+F: drivers/iio/adc/ti-tla2528.c
TEXAS INSTRUMENTS' TMP117 TEMPERATURE SENSOR DRIVER
M: Puranjay Mohan <puranjay@xxxxxxxxxx>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index a802d8ee4dd9..8633267d6056 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -2016,6 +2016,18 @@ config TI_LMP92064
This driver can also be built as a module. If so, the module will be called
ti-lmp92064.
+config TI_TLA2528
+ tristate "Texas Instruments TLA2528 ADC driver"
+ depends on I2C
+ select REGMAP_I2C
+ select IIO_ADC_HELPER
+ help
+ Say yes here to build support for Texas Instruments TLA2528
+ 12-Bit 8-Channel ADC.
+
+ To compile this driver as a module, choose M here: the module will be
+ called ti-tla2528.

I deeply dislike repetitive boilerplate text, which often, in my opinion, provides no real value. This last chapter (which is also present in many other drivers, and which is preferred by some developers) is for me an example of wasted lines. I believe writing the "choose M here: ..." is guidance, specific to menuconfig tool. The purpose of this file is not to explain menuconfig tool usage, but explain what the configuration option enables. Perhaps we some day have different config tool, with no option labeled as 'M' at all.

Furthermore, I do dislike also the "module will be called "foo", which I think is just unnecessary noise. You probably want to still keep it, to avoid comments from other reviewers, who claim someone (if not them) has once used this information for something. ;)

+
config TI_TLC4541
tristate "Texas Instruments TLC4541 ADC driver"
depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 9e82c21dbd37..b98cded4d0c7 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -171,6 +171,7 @@ obj-$(CONFIG_TI_ADS8344) += ti-ads8344.o
obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
obj-$(CONFIG_TI_LMP92064) += ti-lmp92064.o
+obj-$(CONFIG_TI_TLA2528) += ti-tla2528.o
obj-$(CONFIG_TI_TLC4541) += ti-tlc4541.o
obj-$(CONFIG_TI_TSC2046) += ti-tsc2046.o
obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
diff --git a/drivers/iio/adc/ti-tla2528.c b/drivers/iio/adc/ti-tla2528.c
new file mode 100644
index 000000000000..287e52dc9d6d
--- /dev/null
+++ b/drivers/iio/adc/ti-tla2528.c
@@ -0,0 +1,245 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Texas Instruments TLA2528 ADC
+ *
+ * Copyright (C) 2020-2021 Rodolfo Giometti <giometti@xxxxxxxxxxxx>
+ * Copyright (C) 2025 Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
+ */
+
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include <linux/iio/adc-helpers.h>
+#include <linux/iio/iio.h>
+
+#define TLA2528_OP_WRITE_REG 0x08
+#define TLA2528_OP_READ_REG 0x10
+
+#define TLA2528_SYSTEM_STATUS_ADR 0x00
+#define TLA2528_GENERAL_CFG_ADR 0x01
+#define TLA2528_GENERAL_CFG_RST BIT(0)
+#define TLA2528_GPI_VALUE_ADR 0x0d

Not sure having the GPI_VALUE_ADR or SYSTEM_STATUS_ADR here is worth it. They seem to be unused.

+#define TLA2528_CHANNEL_SEL_ADR 0x11
+#define TLA2528_CHANNEL_SEL_MANUAL_CHID GENMASK(3, 0)
+#define TLA2528_AUTO_SEQ_CH_SEL_ADR 0x12
+
+#define TLA2528_NUM_CHANNELS 8
+
+struct tla2528 {
+ struct i2c_client *client;
+ struct regmap *regmap;
+ int vref_mv;
+
+ /* Protects manual channel selection */
+ struct mutex lock;
+};
+
+static bool tla2528_volatile_reg(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ case TLA2528_SYSTEM_STATUS_ADR:
+ case TLA2528_GENERAL_CFG_ADR:
+ case TLA2528_GPI_VALUE_ADR:
+ return true;
+ default:
+ return false;
+ }
+}

My personal preference for static volatile/read-only/write-only register information, is to use range tables. Seeing a function makes me always think there is some runtime logic involved.

This is still nice and clean function, with not much room for confusion so I suppose it is fine.

+static const struct regmap_config tla2528_regmap_config = {
+ .reg_bits = 16,
+ .val_bits = 8,
+ .read_flag_mask = TLA2528_OP_READ_REG,
+ .write_flag_mask = TLA2528_OP_WRITE_REG,
+ .max_register = TLA2528_AUTO_SEQ_CH_SEL_ADR,
+ .volatile_reg = tla2528_volatile_reg,
+ .cache_type = REGCACHE_MAPLE,
+};
+
+static int tla2528_read_sample(const struct i2c_client *client)
+{
+ __be16 data;
+ int ret;
+
+ ret = i2c_master_recv(client, (char *)&data, sizeof(data));
+ if (ret < 0)
+ return ret;
+
+ return be16_to_cpu(data) >> 4;
+}
+
+static int tla2528_read(struct tla2528 *tla2528, u8 channel, int *val)
+{
+ int ret;
+
+ ret = regmap_update_bits(tla2528->regmap, TLA2528_CHANNEL_SEL_ADR,
+ TLA2528_CHANNEL_SEL_MANUAL_CHID, channel);
+ if (ret)
+ return ret;
+
+ ret = tla2528_read_sample(tla2528->client);
+ if (ret < 0)
+ return ret;
+
+ *val = ret;
+
+ return 0;
+}
+
+static int tla2528_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct tla2528 *tla2528 = iio_priv(indio_dev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&tla2528->lock);
+ ret = tla2528_read(tla2528, chan->channel, val);
+ mutex_unlock(&tla2528->lock);
+ if (ret < 0)
+ return ret;
+
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ *val = tla2528->vref_mv;
+ *val2 = 12;
+
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+#define TLA2528_CHAN(chan) { \
+ .type = IIO_VOLTAGE, \
+ .channel = (chan), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+ .indexed = 1, \
+}
+
+static const struct iio_chan_spec tla2528_chan_template = TLA2528_CHAN(0);
+
+static const struct iio_chan_spec tla2528_channel[] = {
+ TLA2528_CHAN(0),
+ TLA2528_CHAN(1),
+ TLA2528_CHAN(2),
+ TLA2528_CHAN(3),
+ TLA2528_CHAN(4),
+ TLA2528_CHAN(5),
+ TLA2528_CHAN(6),
+ TLA2528_CHAN(7),
+};
+
+static const struct iio_info tla2528_info = {
+ .read_raw = tla2528_read_raw,
+};
+
+static int tla2528_probe(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ struct iio_chan_spec *channels;
+ struct iio_dev *indio_dev;
+ struct tla2528 *tla2528;
+ int ret;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+ return -EOPNOTSUPP;
+
+ if (i2c_check_quirks(client->adapter, I2C_AQ_NO_CLK_STRETCH))
+ return dev_err_probe(dev, -EOPNOTSUPP,
+ "adapter does not support clock stretching\n");
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*tla2528));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ tla2528 = iio_priv(indio_dev);
+ tla2528->client = client;
+
+ tla2528->regmap = devm_regmap_init_i2c(client, &tla2528_regmap_config);
+ if (IS_ERR(tla2528->regmap))
+ return PTR_ERR(tla2528->regmap);
+
+ ret = devm_mutex_init(dev, &tla2528->lock);
+ if (ret)
+ return ret;
+
+ ret = devm_regulator_get_enable(dev, "dvdd");
+ if (ret)
+ return ret;
+
+ ret = devm_regulator_get_enable_read_voltage(dev, "avdd");
+ if (ret < 0)
+ return ret;
+
+ tla2528->vref_mv = ret / (MICRO / MILLI);
+
+ ret = devm_iio_adc_device_alloc_chaninfo_se(dev, &tla2528_chan_template,
+ TLA2528_NUM_CHANNELS - 1,
+ &channels);
+ if (ret < 0 && ret != -ENOENT)
+ return ret;
+
+ if (ret == -ENOENT) {
+ indio_dev->channels = tla2528_channel;
+ indio_dev->num_channels = ARRAY_SIZE(tla2528_channel);

I think just requiring the channels to be there would be simpler. It's only 8 chans so it's not that huge description - and this would make it simpler to support "all GPIOs" -case later.

+ } else {
+ indio_dev->channels = channels;
+ indio_dev->num_channels = ret;
+ }
+
+ indio_dev->name = "tla2528";
+ indio_dev->info = &tla2528_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+
+ ret = regmap_write(tla2528->regmap, TLA2528_GENERAL_CFG_ADR,
+ TLA2528_GENERAL_CFG_RST);
+ if (ret)
+ return ret;
+
+ fsleep(5 * USEC_PER_MSEC);
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct i2c_device_id tla2528_id[] = {
+ { "tla2528" },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, tla2528_id);
+
+static const struct of_device_id tla2528_of_match[] = {
+ { .compatible = "ti,tla2528" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, tla2528_of_match);
+
+static struct i2c_driver tla2528_driver = {
+ .driver = {
+ .name = "tla2528",
+ .of_match_table = tla2528_of_match,
+ },
+ .probe = tla2528_probe,
+ .id_table = tla2528_id,
+};
+module_i2c_driver(tla2528_driver);
+
+MODULE_AUTHOR("Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>");
+MODULE_AUTHOR("Rodolfo Giometti <giometti@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Texas Instruments TLA2528 ADC driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_DRIVER");

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~