iio: adc: ad_sigma_delta: add disable_one callback

Sigma delta ADCs with a sequencer need to disable the previously enabled
channel when reading using ad_sigma_delta_single_conversion(). This was
done manually in drivers for devices with sequencers.

This patch implements handling of single channel disabling after a
single conversion.

Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Dumitru Ceclan <dumitru.ceclan@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240607-ad4111-v7-3-97e3855900a0@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dumitruceclan

drivers/iio/adc/ad7124.c

@@ -555,10 +555,18 @@ static int ad7124_disable_all(struct ad_sigma_delta *sd)
 	return 0;
 }
 
+static int ad7124_disable_one(struct ad_sigma_delta *sd, unsigned int chan)
+{
+	struct ad7124_state *st = container_of(sd, struct ad7124_state, sd);
+
+	return ad7124_spi_write_mask(st, AD7124_CHANNEL(chan), AD7124_CHANNEL_EN_MSK, 0, 2);
+}
+
 static const struct ad_sigma_delta_info ad7124_sigma_delta_info = {
 	.set_channel = ad7124_set_channel,
 	.append_status = ad7124_append_status,
 	.disable_all = ad7124_disable_all,
+	.disable_one = ad7124_disable_one,
 	.set_mode = ad7124_set_mode,
 	.has_registers = true,
 	.addr_shift = 0,
@@ -582,12 +590,6 @@ static int ad7124_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		/* After the conversion is performed, disable the channel */
-		ret = ad_sd_write_reg(&st->sd, AD7124_CHANNEL(chan->address), 2,
-				      st->channels[chan->address].ain | AD7124_CHANNEL_EN(0));
-		if (ret < 0)
-			return ret;
-
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		mutex_lock(&st->cfgs_lock);

drivers/iio/adc/ad7173.c

@@ -569,10 +569,16 @@ static int ad7173_disable_all(struct ad_sigma_delta *sd)
 	return 0;
 }
 
+static int ad7173_disable_one(struct ad_sigma_delta *sd, unsigned int chan)
+{
+	return ad_sd_write_reg(sd, AD7173_REG_CH(chan), 2, 0);
+}
+
 static struct ad_sigma_delta_info ad7173_sigma_delta_info = {
 	.set_channel = ad7173_set_channel,
 	.append_status = ad7173_append_status,
 	.disable_all = ad7173_disable_all,
+	.disable_one = ad7173_disable_one,
 	.set_mode = ad7173_set_mode,
 	.has_registers = true,
 	.addr_shift = 0,
@@ -668,11 +674,6 @@ static int ad7173_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		/* disable channel after single conversion */
-		ret = ad_sd_write_reg(&st->sd, AD7173_REG_CH(chan->address), 2, 0);
-		if (ret < 0)
-			return ret;
-
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		if (chan->type == IIO_TEMP) {

drivers/iio/adc/ad_sigma_delta.c

@@ -321,6 +321,7 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev,
 
 	sigma_delta->keep_cs_asserted = false;
 	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);
+	ad_sigma_delta_disable_one(sigma_delta, chan->address);
 	sigma_delta->bus_locked = false;
 	spi_bus_unlock(sigma_delta->spi->controller);
 	iio_device_release_direct_mode(indio_dev);

include/linux/iio/adc/ad_sigma_delta.h

@@ -37,6 +37,10 @@ struct iio_dev;
  * @append_status: Will be called to enable status append at the end of the sample, may be NULL.
  * @set_mode: Will be called to select the current mode, may be NULL.
  * @disable_all: Will be called to disable all channels, may be NULL.
+ * @disable_one: Will be called to disable a single channel after
+ *		ad_sigma_delta_single_conversion(), may be NULL.
+ *		Usage of this callback expects iio_chan_spec.address to contain
+ *		the value required for the driver to identify the channel.
  * @postprocess_sample: Is called for each sampled data word, can be used to
  *		modify or drop the sample data, it, may be NULL.
  * @has_registers: true if the device has writable and readable registers, false
@@ -55,6 +59,7 @@ struct ad_sigma_delta_info {
 	int (*append_status)(struct ad_sigma_delta *, bool append);
 	int (*set_mode)(struct ad_sigma_delta *, enum ad_sigma_delta_mode mode);
 	int (*disable_all)(struct ad_sigma_delta *);
+	int (*disable_one)(struct ad_sigma_delta *, unsigned int chan);
 	int (*postprocess_sample)(struct ad_sigma_delta *, unsigned int raw_sample);
 	bool has_registers;
 	unsigned int addr_shift;
@@ -140,6 +145,15 @@ static inline int ad_sigma_delta_disable_all(struct ad_sigma_delta *sd)
 	return 0;
 }
 
+static inline int ad_sigma_delta_disable_one(struct ad_sigma_delta *sd,
+					     unsigned int chan)
+{
+	if (sd->info->disable_one)
+		return sd->info->disable_one(sd, chan);
+
+	return 0;
+}
+
 static inline int ad_sigma_delta_set_mode(struct ad_sigma_delta *sd,
 	unsigned int mode)
 {