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

[David Lechner <dlechner@baylibre.com>]

On 12/23/25 9:55 AM, Maxime Chevallier wrote:
> This adds a new driver for the TI TLA2528 ADC chip. It ha 8 12-bit

s/This adds/Add/

s/ha/has/

> channels, that can also be configured as 16-bit averaging channels.
> 
> Add a very simple driver for it, allowing reading raw values for each

Don't need to say we are adding a driver twice.

> channel.
> 
> Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> ---
>  MAINTAINERS                  |   7 ++
>  drivers/iio/adc/Kconfig      |  10 ++
>  drivers/iio/adc/Makefile     |   1 +
>  drivers/iio/adc/ti-tla2528.c | 209 +++++++++++++++++++++++++++++++++++
>  4 files changed, 227 insertions(+)
>  create mode 100644 drivers/iio/adc/ti-tla2528.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index dc731d37c8fe..5c382ae216c7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -25866,6 +25866,13 @@ F:	include/dt-bindings/soc/ti,sci_pm_domain.h
>  F:	include/linux/soc/ti/ti_sci_inta_msi.h
>  F:	include/linux/soc/ti/ti_sci_protocol.h
>  
> +TEXAS INSTRUMENTS' TLA2528 ADC DRIVER
> +M:	Maxime Chevallier <maxime.chevallier@bootlin.com>
> +L:	linux-iio@vger.kernel.org
> +S:	Supported
> +F:	Documentation/devicetree/bindings/iio/adc/ti,tla2528.yaml

This part can be included in the dt-bindings patch since that is where
the file is introduced.

> +F:	drivers/iio/adc/ti-tla2528.c

And just keep this line in this patch.

> +
>  TEXAS INSTRUMENTS' TMP117 TEMPERATURE SENSOR DRIVER
>  M:	Puranjay Mohan <puranjay@kernel.org>
>  L:	linux-iio@vger.kernel.org
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 58da8255525e..67376de410bf 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -1803,6 +1803,16 @@ 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
> +	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.
> +
>  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 7cc8f9a12f76..941606defbf7 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -157,6 +157,7 @@ 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..9c572e730ffb
> --- /dev/null
> +++ b/drivers/iio/adc/ti-tla2528.c
> @@ -0,0 +1,209 @@
> +// 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/delay.h>

Check the headers to see what is actually used. For example,
I don't seen any delays/sleeps. And we have a mutex, but no
mutex header.

> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include <linux/iio/iio.h>
> +
> +#define TLA2528_OP_WRITE_REG		0x08
> +
> +#define TLA2528_DATA_CFG_ADR		0x02
> +
> +/* Datasheet says [5:4] sets the append status, but only bit 4 is used */
> +#define TLA2528_DATA_CFG_APPEND_STATUS	BIT(4)
> +#define TLA2528_PIN_CFG_ADR		0x05
> +#define TLA2528_SEQUENCE_CFG_ADR	0x10
> +#define TLA2528_CHANNEL_SEL_ADR		0x11
> +
> +struct tla2528 {
> +	struct i2c_client *client;
> +	int vref_uv;
> +
> +	/* Protects manual channel selection, i.e. last_read_channel */
> +	struct mutex lock;
> +	u8 last_read_channel;
> +};
> +
> +static s32 tla2528_write_reg(const struct i2c_client *client, u8 reg, u8 val)

Usually type is just "int" for error code returns.

> +{
> +	u8 data[3] = {TLA2528_OP_WRITE_REG, reg, val};
> +	int ret;
> +
> +	ret = i2c_master_send(client, data, 3);
> +
> +	return ret < 0 ? ret : 0;
> +}
> +

Would it make sense to use regmap instead?


> +static int tla2528_read_sample(const struct i2c_client *client)
> +{
> +	__be16 data;
> +	int ret;
> +

Don't we need to set the CNVST bit in GENERAL_CFG register to trigger
a conversion in manual mode?

> +	ret = i2c_master_recv(client, (char *)&data, 2);
> +	if (ret < 0)
> +		return ret;
> +
> +	return be16_to_cpu(data) >> 4;
> +}
> +
> +static int tla2528_read(struct tla2528 *tla2528, u8 channel, int *val)
> +{
> +	struct i2c_client *client = tla2528->client;
> +	int ret;
> +
> +	if (channel != tla2528->last_read_channel) {
> +		ret = tla2528_write_reg(client, TLA2528_CHANNEL_SEL_ADR, channel);
> +		if (ret < 0)
> +			return ret;
> +
> +		tla2528->last_read_channel = channel;
> +	}

If we implemented regmap with cache, then we could avoid having to
track last_read_channel. We could just call regmap_write() unconditionally
and the regmap framework would decide if it needs to actually do the write
or not.

> +
> +	ret = tla2528_read_sample(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_uv / 1000;

Why not just store vref_mV?

> +		*val2 = 12;
> +
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +#define TLA2528_CHAN(_chan, _name) { \
> +	.type = IIO_VOLTAGE,					\
> +	.channel = (_chan),					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +	.datasheet_name = _name,				\
> +	.indexed = 1,						\
> +}
> +
> +static const struct iio_chan_spec tla2528_channel[] = {
> +	TLA2528_CHAN(0, "AIN0"),
> +	TLA2528_CHAN(1, "AIN1"),
> +	TLA2528_CHAN(2, "AIN2"),
> +	TLA2528_CHAN(3, "AIN3"),
> +	TLA2528_CHAN(4, "AIN4"),
> +	TLA2528_CHAN(5, "AIN5"),
> +	TLA2528_CHAN(6, "AIN6"),
> +	TLA2528_CHAN(7, "AIN7"),
> +};
> +
> +static const struct iio_info tla2528_info = {
> +	.read_raw = tla2528_read_raw,
> +};
> +
> +static int tla2528_probe(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev;
> +	struct tla2528 *tla2528;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
> +				     I2C_FUNC_SMBUS_WRITE_WORD_DATA))
> +		return -EOPNOTSUPP;

Perhaps we should also fail if the adapter has I2C_AQ_NO_CLK_STRETCH?
It looks like clock stretching is required for the conversion time.

> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*tla2528));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	tla2528 = iio_priv(indio_dev);

> +	i2c_set_clientdata(client, indio_dev);

Not sure this is needed if there is no i2c_get_clientdata() anywhere.

> +	tla2528->client = client;
> +

> +	indio_dev->name = client->name;

This should be the chip name ("tla2528"), not the I2C device name.

> +	indio_dev->info = &tla2528_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = tla2528_channel;
> +	indio_dev->num_channels = ARRAY_SIZE(tla2528_channel);
> +
> +	mutex_init(&tla2528->lock);

Use dem_mutex_init().

> +
> +	tla2528->vref_uv = devm_regulator_get_enable_read_voltage(&client->dev,
> +								  "vref");
> +	if (tla2528->vref_uv < 0)
> +		return tla2528->vref_uv;
> +

> +	/* Set all inputs as analog */
> +	ret = tla2528_write_reg(tla2528->client, TLA2528_PIN_CFG_ADR, 0x00);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = tla2528_write_reg(tla2528->client, TLA2528_DATA_CFG_ADR,
> +				TLA2528_DATA_CFG_APPEND_STATUS);

Why? It doesn't appear to be used.

> +	if (ret < 0)
> +		return ret;
> +
> +	/* Set manual mode */
> +	ret = tla2528_write_reg(tla2528->client, TLA2528_SEQUENCE_CFG_ADR, 0x00);
> +	if (ret < 0)
> +		return ret;
> +


Perhaps simpler to just write the RST bit GENERAL_CFG to reset everything
to a known state?


> +	/* Init private data */
> +	tla2528->last_read_channel = ~0;
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id tla2528_id[] = {
> +	{ "tla2528", 0 },
> +	{ }
> +};
> +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");