[PATCH v2 6/6] meson saradc: support reading from channel7 mux inputs

[George Stark]

Add iio channel for every channel 7 muxer input.
Meson saradc channel 7 is connected to muxer that can switch channel
input to well-known sources like Vdd, GND and several Vdd dividers.

Signed-off-by: George Stark <GNStark at sberdevices.ru>
---

Changelog:
v1->v2: update commit message from [1]

[1] https://lore.kernel.org/lkml/20230621062715.455652-4-gnstark@sberdevices.ru/

---
 drivers/iio/adc/meson_saradc.c | 65 +++++++++++++++++++++++++++++++---
 1 file changed, 61 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
index e7eb154b151f..ecaebb569e8e 100644
--- a/drivers/iio/adc/meson_saradc.c
+++ b/drivers/iio/adc/meson_saradc.c
@@ -163,6 +163,7 @@
 #define MESON_SAR_ADC_MAX_FIFO_SIZE				32
 #define MESON_SAR_ADC_TIMEOUT					100 /* ms */
 #define MESON_SAR_ADC_VOLTAGE_AND_TEMP_CHANNEL			6
+#define MESON_SAR_ADC_VOLTAGE_AND_MUX_CHANNEL			7
 #define MESON_SAR_ADC_TEMP_OFFSET				27
 
 /* temperature sensor calibration information in eFuse */
@@ -201,6 +202,19 @@
 	.datasheet_name = "TEMP_SENSOR",				\
 }
 
+#define MESON_SAR_ADC_MUX(_chan, _sel) {				\
+	.type = IIO_VOLTAGE,						\
+	.channel = _chan,						\
+	.indexed = 1,							\
+	.address = MESON_SAR_ADC_VOLTAGE_AND_MUX_CHANNEL,		\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |	\
+				BIT(IIO_CHAN_INFO_CALIBSCALE),		\
+	.datasheet_name = "SAR_ADC_MUX_"#_sel,				\
+}
+
 enum meson_sar_adc_avg_mode {
 	NO_AVERAGING = 0x0,
 	MEAN_AVERAGING = 0x1,
@@ -233,6 +247,27 @@ enum meson_sar_adc_channel_index {
 	INDEX_CHAN_6,
 	INDEX_CHAN_7,
 	INDEX_CHAN_SOFT_TIMESTAMP,
+	INDEX_MUX_0_VSS,
+	INDEX_MUX_1_VDD_DIV4,
+	INDEX_MUX_2_VDD_DIV2,
+	INDEX_MUX_3_VDD_MUL3_DIV4,
+	INDEX_MUX_4_VDD,
+};
+
+static enum meson_sar_adc_chan7_mux_sel chan7_mux_values[] = {
+	CHAN7_MUX_VSS,
+	CHAN7_MUX_VDD_DIV4,
+	CHAN7_MUX_VDD_DIV2,
+	CHAN7_MUX_VDD_MUL3_DIV4,
+	CHAN7_MUX_VDD,
+};
+
+static const char * const chan7_mux_names[] = {
+	"gnd",
+	"0.25vdd",
+	"0.5vdd",
+	"0.75vdd",
+	"vdd",
 };
 
 static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
@@ -245,6 +280,11 @@ static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
 	MESON_SAR_ADC_CHAN(INDEX_CHAN_6),
 	MESON_SAR_ADC_CHAN(INDEX_CHAN_7),
 	IIO_CHAN_SOFT_TIMESTAMP(INDEX_CHAN_SOFT_TIMESTAMP),
+	MESON_SAR_ADC_MUX(INDEX_MUX_0_VSS, 0),
+	MESON_SAR_ADC_MUX(INDEX_MUX_1_VDD_DIV4, 1),
+	MESON_SAR_ADC_MUX(INDEX_MUX_2_VDD_DIV2, 2),
+	MESON_SAR_ADC_MUX(INDEX_MUX_3_VDD_MUL3_DIV4, 3),
+	MESON_SAR_ADC_MUX(INDEX_MUX_4_VDD, 4),
 	MESON_SAR_ADC_TEMP_CHAN(), /* must be the last item */
 };
 
@@ -284,6 +324,7 @@ struct meson_sar_adc_priv {
 	bool					temperature_sensor_calibrated;
 	u8					temperature_sensor_coefficient;
 	u16					temperature_sensor_adc_val;
+	enum meson_sar_adc_chan7_mux_sel	chan7_mux_sel;
 };
 
 static const struct regmap_config meson_sar_adc_regmap_config_gxbb = {
@@ -348,6 +389,8 @@ static void meson_sar_adc_set_chan7_mux(struct iio_dev *indio_dev,
 			   MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);
 
 	usleep_range(10, 20);
+
+	priv->chan7_mux_sel = sel;
 }
 
 static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
@@ -443,6 +486,15 @@ static void meson_sar_adc_enable_channel(struct iio_dev *indio_dev,
 		regmap_update_bits(priv->regmap,
 				   MESON_SAR_ADC_DELTA_10,
 				   MESON_SAR_ADC_DELTA_10_TEMP_SEL, regval);
+	} else if (chan->address == MESON_SAR_ADC_VOLTAGE_AND_MUX_CHANNEL) {
+		enum meson_sar_adc_chan7_mux_sel sel;
+
+		if (chan->channel == INDEX_CHAN_7)
+			sel = CHAN7_MUX_CH7_INPUT;
+		else
+			sel = chan7_mux_values[chan->channel - INDEX_MUX_0_VSS];
+		if (sel != priv->chan7_mux_sel)
+			meson_sar_adc_set_chan7_mux(indio_dev, sel);
 	}
 }
 
@@ -1015,7 +1067,7 @@ static int meson_sar_adc_calib(struct iio_dev *indio_dev)
 	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_DIV4);
 	usleep_range(10, 20);
 	ret = meson_sar_adc_get_sample(indio_dev,
-				       &indio_dev->channels[INDEX_CHAN_7],
+				       &indio_dev->channels[INDEX_MUX_1_VDD_DIV4],
 				       MEAN_AVERAGING, EIGHT_SAMPLES, &value0);
 	if (ret < 0)
 		goto out;
@@ -1023,7 +1075,7 @@ static int meson_sar_adc_calib(struct iio_dev *indio_dev)
 	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_MUL3_DIV4);
 	usleep_range(10, 20);
 	ret = meson_sar_adc_get_sample(indio_dev,
-				       &indio_dev->channels[INDEX_CHAN_7],
+				       &indio_dev->channels[INDEX_MUX_3_VDD_MUL3_DIV4],
 				       MEAN_AVERAGING, EIGHT_SAMPLES, &value1);
 	if (ret < 0)
 		goto out;
@@ -1050,8 +1102,13 @@ static int read_label(struct iio_dev *indio_dev,
 {
 	if (chan->type == IIO_TEMP)
 		return sprintf(label, "%s\n", "temp-sensor");
-	if (chan->type == IIO_VOLTAGE)
-		return sprintf(label, "channel-%d\n", chan->channel);
+	if (chan->type == IIO_VOLTAGE) {
+		if (chan->channel <= INDEX_CHAN_7)
+			return sprintf(label, "channel-%d\n", chan->channel);
+		if (chan->channel >= INDEX_MUX_0_VSS)
+			return sprintf(label, "%s\n",
+				chan7_mux_names[chan->channel - INDEX_MUX_0_VSS]);
+	}
 	return 0;
 }
 
-- 
2.38.4