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

["Ceclan, Dumitru" <mitrutzceclan@gmail.com>]

On 16/05/2024 02:27, David Lechner wrote:
> 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.
> 
As I've said, I do not agree with forcing one channel slot to be used.
I could add a property that spawns this channel. Although as I see under,
I think I'll permit these inputs to be mixed and matched.

> 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.
> 
This is imposed artificially, AD411x has the same cross-point mux that
can mix and match all the inputs.

> 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?
>

I think it is 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
>>
>>