Re: [PATCH v2 5/9] iio: adc: ad7173: add support for special inputs

[David Lechner <dlechner@baylibre.com>]

On Tue, May 14, 2024 at 2:23 AM Dumitru Ceclan via B4 Relay
<devnull+dumitru.ceclan.analog.com@kernel.org> wrote:
>
> From: Dumitru Ceclan <dumitru.ceclan@analog.com>
>
>  Add support for selecting REF+ and REF- inputs on all models.
>  Add support for selecting ((AVDD1 − AVSS)/5) inputs
>   on supported models.
>
> Signed-off-by: Dumitru Ceclan <dumitru.ceclan@analog.com>
> ---
>  drivers/iio/adc/ad7173.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
> index fb33534d63a9..1e9ba3070770 100644
> --- a/drivers/iio/adc/ad7173.c
> +++ b/drivers/iio/adc/ad7173.c
> @@ -65,6 +65,10 @@
>          FIELD_PREP(AD7173_CH_SETUP_AINNEG_MASK, neg))
>  #define AD7173_AIN_TEMP_POS    17
>  #define AD7173_AIN_TEMP_NEG    18
> +#define AD7173_AIN_COM_IN_POS  19
> +#define AD7173_AIN_COM_IN_NEG  20
> +#define AD7173_AIN_REF_POS     21
> +#define AD7173_AIN_REF_NEG     22
>
>  #define AD7172_2_ID                    0x00d0
>  #define AD7175_ID                      0x0cd0
> @@ -145,6 +149,8 @@ struct ad7173_device_info {
>         unsigned int id;
>         char *name;
>         bool has_temp;
> +       /* ((AVDD1 − AVSS)/5) */
> +       bool has_common_input;
>         bool has_input_buf;
>         bool has_int_ref;
>         bool has_ref2;
> @@ -215,6 +221,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_temp = true,
>                 .has_input_buf = true,
>                 .has_int_ref = true,
> +               .has_common_input = true,
>                 .clock = 2 * HZ_PER_MHZ,
>                 .sinc5_data_rates = ad7173_sinc5_data_rates,
>                 .num_sinc5_data_rates = ARRAY_SIZE(ad7173_sinc5_data_rates),
> @@ -228,6 +235,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_temp = false,
>                 .has_input_buf = true,
>                 .has_ref2 = true,
> +               .has_common_input = true,
>                 .clock = 2 * HZ_PER_MHZ,
>                 .sinc5_data_rates = ad7173_sinc5_data_rates,
>                 .num_sinc5_data_rates = ARRAY_SIZE(ad7173_sinc5_data_rates),
> @@ -243,6 +251,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_input_buf = true,
>                 .has_int_ref = true,
>                 .has_ref2 = true,
> +               .has_common_input = false,
>                 .clock = 2 * HZ_PER_MHZ,
>                 .sinc5_data_rates = ad7173_sinc5_data_rates,
>                 .num_sinc5_data_rates = ARRAY_SIZE(ad7173_sinc5_data_rates),
> @@ -257,6 +266,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_temp = true,
>                 .has_input_buf = true,
>                 .has_int_ref = true,
> +               .has_common_input = true,
>                 .clock = 16 * HZ_PER_MHZ,
>                 .sinc5_data_rates = ad7175_sinc5_data_rates,
>                 .num_sinc5_data_rates = ARRAY_SIZE(ad7175_sinc5_data_rates),
> @@ -271,6 +281,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_input_buf = true,
>                 .has_int_ref = true,
>                 .has_ref2 = true,
> +               .has_common_input = true,
>                 .clock = 16 * HZ_PER_MHZ,
>                 .sinc5_data_rates = ad7175_sinc5_data_rates,
>                 .num_sinc5_data_rates = ARRAY_SIZE(ad7175_sinc5_data_rates),
> @@ -285,6 +296,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_temp = false,
>                 .has_input_buf = false,
>                 .has_int_ref = true,
> +               .has_common_input = false,
>                 .clock = 16 * HZ_PER_MHZ,
>                 .sinc5_data_rates = ad7175_sinc5_data_rates,
>                 .num_sinc5_data_rates = ARRAY_SIZE(ad7175_sinc5_data_rates),
> @@ -298,6 +310,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
>                 .has_temp = true,
>                 .has_input_buf = true,
>                 .has_int_ref = true,
> +               .has_common_input = true,
>                 .clock = 16 * HZ_PER_MHZ,
>                 .odr_start_value = AD7177_ODR_START_VALUE,
>                 .sinc5_data_rates = ad7175_sinc5_data_rates,
> @@ -920,6 +933,14 @@ static int ad7173_validate_voltage_ain_inputs(struct ad7173_state *st,
>                 if (ain[i] < st->info->num_inputs)
>                         continue;
>
> +               if (ain[i] == AD7173_AIN_REF_POS || ain[i] == AD7173_AIN_REF_NEG)
> +                       continue;
> +
> +               if ((ain[i] == AD7173_AIN_COM_IN_POS ||
> +                    ain[i] == AD7173_AIN_COM_IN_NEG) &&
> +                   st->info->has_common_input)
> +                       continue;
> +

If there is only one valid combination, it seems like these should be
fixed channels like the temperature input rather than something coming
from the device tree.

It looks like on AD411x, it is the case that there is only one valid
option for the reference input in the channel configuration. But in
the case of AD717x since both REF+ and REF- are listed as possible
inputs for both AINPOS0 and AINNEG0, it seems like they could be mixed
and matched with other channels. The datasheet doesn't seem very clear
on this though.

If it is valid to combine, say AIN0 with REF+ though, then the
validation would need to be relaxed. But I'm guessing that is not
actually the case?

>                 return dev_err_probe(dev, -EINVAL,
>                         "Input pin number out of range for pair (%d %d).\n",
>                         ain[0], ain[1]);
>
> --
> 2.43.0
>
>