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

From: Sukrut Bellary
Date: Wed Apr 09 2025 - 17:42:41 EST

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On Tue, Apr 08, 2025 at 03:57:32PM -0500, David Lechner wrote:
> 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.

Thanks for the review.
Ok, I will improve in 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?

* were part of comments. I will fix line wrapping.

> * ... 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.

Ok, I will try with helper in v4.

> > 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.

Sure, I will drop storagebits.

> > + .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)
> };
>
> ...

OK, I will remove enum.

> >
> > 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.

This is not a cleanup. Addressed the review comments on v1 i.e., to
arrange of_device_id and spi_device_id in a numeric order. And added
more device ids used enum.

> >
> > 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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