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

[Matti Vaittinen <mazziesaccount@gmail.com>]

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@enneenne.com>
> Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

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@gmail.com>

> ---
>   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@bootlin.com>
>   L:	linux-iio@vger.kernel.org
>   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@kernel.org>
> 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@enneenne.com>
> + * Copyright (C) 2025 Maxime Chevallier <maxime.chevallier@bootlin.com>
> + */
> +
> +#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@bootlin.com>");
> +MODULE_AUTHOR("Rodolfo Giometti <giometti@enneenne.com>");
> +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

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