Re: [PATCH 2/2] iio: adc: ti-adc128s052: Add lower resolution devices support

From: David Lechner
Date: Tue Apr 08 2025 - 16:58:28 EST

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In reply to: Sukrut Bellary: "[PATCH 2/2] iio: adc: ti-adc128s052: Add lower resolution devices support"
Next in thread: Sukrut Bellary: "Re: [PATCH 2/2] iio: adc: ti-adc128s052: Add lower resolution devices support"
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On 4/8/25 8:21 AM, Sukrut Bellary wrote:
> The adcxx4s communicates with a host processor via an SPI/Microwire Bus
> interface. The device family responds with 12-bit data, of which the LSB
> bits are transmitted by the lower resolution devices as 0.
> The unavailable bits are 0 in LSB.
> Shift is calculated per resolution and used in scaling and
> raw data read.

Could improve the line wrapping in the commit message if there is a v4.

>
> Lets reuse the driver to support the family of devices with name
> ADC<bb><c>S<sss>, where
> * bb is the resolution in number of bits (8, 10, 12)
> * c is the number of channels (1, 2, 4, 8)
> * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
> and 101 for 1 MSPS)
>
> Complete datasheets are available at TI's website here:
> https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf
>
> Tested only with ti-adc102s051 on BegalePlay SBC.
> https://www.beagleboard.org/boards/beagleplay
>
> Co-developed-by: Nishanth Menon <nm@xxxxxx>
> Signed-off-by: Nishanth Menon <nm@xxxxxx>
> Signed-off-by: Sukrut Bellary <sbellary@xxxxxxxxxxxx>
> ---

I didn't see any serious issues, just some room for more polish...

> Changes in v3:
> - used be16_to_cpu() for the endian conversion.
> - used config index enum while setting up the adc128_config[]
>
> - Link to v2:
> https://lore.kernel.org/lkml/20231022031203.632153-1-sukrut.bellary@xxxxxxxxx/
>
> Changes in v2:
> - Arranged of_device_id and spi_device_id in numeric order.
> - Used enum to index into adc128_config.
> - Reorder adc128_config in alphabetical.
> - Include channel resolution information.
> - Shift is calculated per resolution and used in scaling and
> raw data read.
>
> - Link to v1: https://lore.kernel.org/all/20220701042919.18180-1-nm@xxxxxx/
> ---
> drivers/iio/adc/ti-adc128s052.c | 149 ++++++++++++++++++++++++--------
> 1 file changed, 112 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
> index a456ea78462f..d4b76fd85abd 100644
> --- a/drivers/iio/adc/ti-adc128s052.c
> +++ b/drivers/iio/adc/ti-adc128s052.c
> @@ -7,6 +7,22 @@
> * https://www.ti.com/lit/ds/symlink/adc128s052.pdf
> * https://www.ti.com/lit/ds/symlink/adc122s021.pdf
> * https://www.ti.com/lit/ds/symlink/adc124s021.pdf
> + *
> + * The adcxx4s communicates with a host processor via an SPI/Microwire Bus
> + * interface. This driver supports the whole family of devices with a name
> + * ADC<bb><c>S<sss>, where
> + * bb is the resolution in number of bits (8, 10, 12)
> + * c is the number of channels (1, 2, 4, 8)
> + * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
> + * and 101 for 1 MSPS)

Looks like odd line wrapping. I assume bullet points were meant here?

* ... where:
* - bb is ...
* - c is ...
* - sss is ...

> + *
> + * Complete datasheets are available at TI's website here:
> + * https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf
> + *
> + * 8, 10, and 12 bits converters send 12-bit data with
> + * unavailable bits set to 0 in LSB.
> + * Shift is calculated per resolution and used in scaling and
> + * raw data read.
> */
>
> #include <linux/err.h>
> @@ -53,7 +69,7 @@ static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
> if (ret < 0)
> return ret;
>
> - return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
> + return be16_to_cpu(*((__be16 *)adc->buffer));
> }
>
> static int adc128_read_raw(struct iio_dev *indio_dev,
> @@ -70,7 +86,8 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
> if (ret < 0)
> return ret;
>
> - *val = ret;
> + *val = (ret >> channel->scan_type.shift) &
> + GENMASK(channel->scan_type.realbits - 1, 0);

It's a bit odd to do this here instead of in the helper function since
the helper function is doing some rearranging of bits already.

Could pass scan_type to the helper function and do it all in one
place.

> return IIO_VAL_INT;
>
> case IIO_CHAN_INFO_SCALE:
> @@ -80,7 +97,7 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
> return ret;
>
> *val = ret / 1000;
> - *val2 = 12;
> + *val2 = channel->scan_type.realbits;
> return IIO_VAL_FRACTIONAL_LOG2;
>
> default:
> @@ -89,24 +106,34 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
>
> }
>
> -#define ADC128_VOLTAGE_CHANNEL(num) \
> - { \
> - .type = IIO_VOLTAGE, \
> - .indexed = 1, \
> - .channel = (num), \
> - .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> - .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
> +#define _ADC128_VOLTAGE_CHANNEL(num, real_bits, store_bits) \
> + { \
> + .type = IIO_VOLTAGE, \
> + .indexed = 1, \
> + .channel = (num), \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .scan_index = (num), \
> + .scan_type = { \
> + .sign = 'u', \
> + .realbits = (real_bits), \
> + .storagebits = (store_bits), \

It looks like storagebits is always 16, so we could drop that parameter.

> + .shift = (12 - real_bits), \
> + }, \
> }
>
> -static const struct iio_chan_spec adc128s052_channels[] = {
> - ADC128_VOLTAGE_CHANNEL(0),
> - ADC128_VOLTAGE_CHANNEL(1),
> - ADC128_VOLTAGE_CHANNEL(2),
> - ADC128_VOLTAGE_CHANNEL(3),
> - ADC128_VOLTAGE_CHANNEL(4),
> - ADC128_VOLTAGE_CHANNEL(5),
> - ADC128_VOLTAGE_CHANNEL(6),
> - ADC128_VOLTAGE_CHANNEL(7),
> +#define ADC082_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 8, 16)
> +#define ADC102_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 10, 16)
> +#define ADC128_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 12, 16)
> +
> +static const struct iio_chan_spec adc082s021_channels[] = {
> + ADC082_VOLTAGE_CHANNEL(0),
> + ADC082_VOLTAGE_CHANNEL(1),
> +};
> +
> +static const struct iio_chan_spec adc102s021_channels[] = {
> + ADC102_VOLTAGE_CHANNEL(0),
> + ADC102_VOLTAGE_CHANNEL(1),
> };
>
> static const struct iio_chan_spec adc122s021_channels[] = {
> @@ -121,10 +148,46 @@ static const struct iio_chan_spec adc124s021_channels[] = {
> ADC128_VOLTAGE_CHANNEL(3),
> };
>
> +static const struct iio_chan_spec adc128s052_channels[] = {
> + ADC128_VOLTAGE_CHANNEL(0),
> + ADC128_VOLTAGE_CHANNEL(1),
> + ADC128_VOLTAGE_CHANNEL(2),
> + ADC128_VOLTAGE_CHANNEL(3),
> + ADC128_VOLTAGE_CHANNEL(4),
> + ADC128_VOLTAGE_CHANNEL(5),
> + ADC128_VOLTAGE_CHANNEL(6),
> + ADC128_VOLTAGE_CHANNEL(7),
> +};
> +
> +enum adc128_configuration_index {
> + ADC128_CONFIG_INDEX_082S,
> + ADC128_CONFIG_INDEX_102S,
> + ADC128_CONFIG_INDEX_122S,
> + ADC128_CONFIG_INDEX_124S,
> + ADC128_CONFIG_INDEX_128S,
> +};
> +
> static const struct adc128_configuration adc128_config[] = {

I would have rather removed the array here. Adding the enum just
makes lots more code to read without any technical benefit.

> - { adc128s052_channels, ARRAY_SIZE(adc128s052_channels) },
> - { adc122s021_channels, ARRAY_SIZE(adc122s021_channels) },
> - { adc124s021_channels, ARRAY_SIZE(adc124s021_channels) },
> + [ADC128_CONFIG_INDEX_082S] = {
> + .channels = adc082s021_channels,
> + .num_channels = ARRAY_SIZE(adc082s021_channels)
> + },
> + [ADC128_CONFIG_INDEX_102S] = {
> + .channels = adc102s021_channels,
> + .num_channels = ARRAY_SIZE(adc102s021_channels)
> + },
> + [ADC128_CONFIG_INDEX_122S] = {
> + .channels = adc122s021_channels,
> + .num_channels = ARRAY_SIZE(adc122s021_channels)
> + },
> + [ADC128_CONFIG_INDEX_124S] = {
> + .channels = adc124s021_channels,
> + .num_channels = ARRAY_SIZE(adc124s021_channels)
> + },
> + [ADC128_CONFIG_INDEX_128S] = {
> + .channels = adc128s052_channels,
> + .num_channels = ARRAY_SIZE(adc128s052_channels)
> + },
> };

I.e. instead:

static const struct adc128_configuration adc08s021_config = {
.channels = adc082s021_channels,
.num_channels = ARRAY_SIZE(adc082s021_channels),
};

static const struct adc128_configuration adc10s021_config = {
.channels = adc102s021_channels,
.num_channels = ARRAY_SIZE(adc102s021_channels)
};

...

>
> static const struct iio_info adc128_info = {
> @@ -177,31 +240,43 @@ static int adc128_probe(struct spi_device *spi)
> }
>
> static const struct of_device_id adc128_of_match[] = {
> - { .compatible = "ti,adc128s052", .data = &adc128_config[0] },
> - { .compatible = "ti,adc122s021", .data = &adc128_config[1] },
> - { .compatible = "ti,adc122s051", .data = &adc128_config[1] },
> - { .compatible = "ti,adc122s101", .data = &adc128_config[1] },
> - { .compatible = "ti,adc124s021", .data = &adc128_config[2] },
> - { .compatible = "ti,adc124s051", .data = &adc128_config[2] },
> - { .compatible = "ti,adc124s101", .data = &adc128_config[2] },
> + { .compatible = "ti,adc082s021", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
> + { .compatible = "ti,adc082s051", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
> + { .compatible = "ti,adc082s101", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
> + { .compatible = "ti,adc102s021", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
> + { .compatible = "ti,adc102s051", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
> + { .compatible = "ti,adc102s101", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
> + { .compatible = "ti,adc122s021", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
> + { .compatible = "ti,adc122s051", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
> + { .compatible = "ti,adc122s101", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
> + { .compatible = "ti,adc124s021", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
> + { .compatible = "ti,adc124s051", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
> + { .compatible = "ti,adc124s101", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
> + { .compatible = "ti,adc128s052", .data = &adc128_config[ADC128_CONFIG_INDEX_128S] },
> { /* sentinel */ },
> };
> MODULE_DEVICE_TABLE(of, adc128_of_match);

It would be easier to see what is new and what is changed if we split out the
"cleanup" to a separate patch.

>
> static const struct spi_device_id adc128_id[] = {
> - { "adc128s052", (kernel_ulong_t)&adc128_config[0] },
> - { "adc122s021", (kernel_ulong_t)&adc128_config[1] },
> - { "adc122s051", (kernel_ulong_t)&adc128_config[1] },
> - { "adc122s101", (kernel_ulong_t)&adc128_config[1] },
> - { "adc124s021", (kernel_ulong_t)&adc128_config[2] },
> - { "adc124s051", (kernel_ulong_t)&adc128_config[2] },
> - { "adc124s101", (kernel_ulong_t)&adc128_config[2] },
> + { "adc082s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
> + { "adc082s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
> + { "adc082s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
> + { "adc102s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
> + { "adc102s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
> + { "adc102s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
> + { "adc122s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
> + { "adc122s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
> + { "adc122s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
> + { "adc124s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> + { "adc124s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> + { "adc124s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> + { "adc128s052", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_128S] },
> { }
> };
> MODULE_DEVICE_TABLE(spi, adc128_id);
>
> static const struct acpi_device_id adc128_acpi_match[] = {
> - { "AANT1280", (kernel_ulong_t)&adc128_config[2] },
> + { "AANT1280", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> { }
> };
> MODULE_DEVICE_TABLE(acpi, adc128_acpi_match);

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In reply to: Sukrut Bellary: "[PATCH 2/2] iio: adc: ti-adc128s052: Add lower resolution devices support"
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