iio: adc: ad7173: add support for special inputs

 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>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240607-ad4111-v7-6-97e3855900a0@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dumitruceclan

drivers/iio/adc/ad7173.c

@@ -66,6 +66,13 @@
 	 FIELD_PREP(AD7173_CH_SETUP_AINNEG_MASK, neg))
 #define AD7173_AIN_TEMP_POS	17
 #define AD7173_AIN_TEMP_NEG	18
+#define AD7173_AIN_POW_MON_POS	19
+#define AD7173_AIN_POW_MON_NEG	20
+#define AD7173_AIN_REF_POS	21
+#define AD7173_AIN_REF_NEG	22
+
+#define AD7173_IS_REF_INPUT(x)		((x) == AD7173_AIN_REF_POS || \
+					(x) == AD7173_AIN_REF_NEG)
 
 #define AD7172_2_ID			0x00d0
 #define AD7175_ID			0x0cd0
@@ -146,6 +153,8 @@ struct ad7173_device_info {
 	unsigned int id;
 	char *name;
 	bool has_temp;
+	/* ((AVDD1 − AVSS)/5) */
+	bool has_pow_supply_monitoring;
 	bool has_input_buf;
 	bool has_int_ref;
 	bool has_ref2;
@@ -216,6 +225,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
 		.has_temp = true,
 		.has_input_buf = true,
 		.has_int_ref = true,
+		.has_pow_supply_monitoring = true,
 		.clock = 2 * HZ_PER_MHZ,
 		.sinc5_data_rates = ad7173_sinc5_data_rates,
 		.num_sinc5_data_rates = ARRAY_SIZE(ad7173_sinc5_data_rates),
@@ -230,6 +240,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
 		.has_temp = false,
 		.has_input_buf = true,
 		.has_ref2 = true,
+		.has_pow_supply_monitoring = true,
 		.clock = 2 * HZ_PER_MHZ,
 		.sinc5_data_rates = ad7173_sinc5_data_rates,
 		.num_sinc5_data_rates = ARRAY_SIZE(ad7173_sinc5_data_rates),
@@ -259,6 +270,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
 		.has_temp = true,
 		.has_input_buf = true,
 		.has_int_ref = true,
+		.has_pow_supply_monitoring = true,
 		.clock = 16 * HZ_PER_MHZ,
 		.sinc5_data_rates = ad7175_sinc5_data_rates,
 		.num_sinc5_data_rates = ARRAY_SIZE(ad7175_sinc5_data_rates),
@@ -274,6 +286,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
 		.has_input_buf = true,
 		.has_int_ref = true,
 		.has_ref2 = true,
+		.has_pow_supply_monitoring = true,
 		.clock = 16 * HZ_PER_MHZ,
 		.sinc5_data_rates = ad7175_sinc5_data_rates,
 		.num_sinc5_data_rates = ARRAY_SIZE(ad7175_sinc5_data_rates),
@@ -302,6 +315,7 @@ static const struct ad7173_device_info ad7173_device_info[] = {
 		.has_temp = true,
 		.has_input_buf = true,
 		.has_int_ref = true,
+		.has_pow_supply_monitoring = true,
 		.clock = 16 * HZ_PER_MHZ,
 		.odr_start_value = AD7177_ODR_START_VALUE,
 		.sinc5_data_rates = ad7175_sinc5_data_rates,
@@ -910,9 +924,18 @@ static int ad7173_validate_voltage_ain_inputs(struct ad7173_state *st,
 					      unsigned int ain0, unsigned int ain1)
 {
 	struct device *dev = &st->sd.spi->dev;
+	bool special_input0, special_input1;
+
+	/* (AVDD1-AVSS)/5 power supply monitoring */
+	if (ain0 == AD7173_AIN_POW_MON_POS && ain1 == AD7173_AIN_POW_MON_NEG &&
+	    st->info->has_pow_supply_monitoring)
+		return 0;
+
+	special_input0 = AD7173_IS_REF_INPUT(ain0);
+	special_input1 = AD7173_IS_REF_INPUT(ain1);
 
-	if (ain0 >= st->info->num_inputs ||
-	    ain1 >= st->info->num_inputs)
+	if ((ain0 >= st->info->num_inputs && !special_input0) ||
+	    (ain1 >= st->info->num_inputs && !special_input1))
 		return dev_err_probe(dev, -EINVAL,
 				     "Input pin number out of range for pair (%d %d).\n",
 				     ain0, ain1);