linux-kernel - [PATCH v6 2/3] iio: adc: tsc2046: add vref support

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Date:   Sun,  4 Sep 2022 12:02:02 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org
Subject: [PATCH v6 2/3] iio: adc: tsc2046: add vref support

If VREF pin is attached, we should use external VREF source instead of
the internal. Otherwise we will get wrong measurements on some of the channel
types.

Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
---
changes v6:
- optimize struct padding and reduce size from 480 to 472 bytes.
changes v5:
- add "the" before channel
- refactor error handling on regulator registration
- use MILLI instead of 1000
changes v4:
- use vref_reg pointer instead of bool use_internal_vref
- move regulator registration to a separate function
- rework error handling
- add devm_add_action_or_reset
---
 drivers/iio/adc/ti-tsc2046.c | 57 ++++++++++++++++++++++++++++++++++--
 1 file changed, 55 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ti-tsc2046.c b/drivers/iio/adc/ti-tsc2046.c
index 0d9436a69cbfb..8d6559303172f 100644
--- a/drivers/iio/adc/ti-tsc2046.c
+++ b/drivers/iio/adc/ti-tsc2046.c
@@ -8,7 +8,9 @@
 #include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/module.h>
+#include <linux/regulator/consumer.h>
 #include <linux/spi/spi.h>
+#include <linux/units.h>
 
 #include <asm/unaligned.h>
 
@@ -139,6 +141,7 @@ enum tsc2046_state {
 struct tsc2046_adc_priv {
 	struct spi_device *spi;
 	const struct tsc2046_adc_dcfg *dcfg;
+	struct regulator *vref_reg;
 
 	struct iio_trigger *trig;
 	struct hrtimer trig_timer;
@@ -173,6 +176,7 @@ struct tsc2046_adc_priv {
 	u32 scan_interval_us;
 	u32 time_per_scan_us;
 	u32 time_per_bit_ns;
+	unsigned int vref_mv;
 
 	struct tsc2046_adc_ch_cfg ch_cfg[TI_TSC2046_MAX_CHAN];
 };
@@ -252,7 +256,9 @@ static u8 tsc2046_adc_get_cmd(struct tsc2046_adc_priv *priv, int ch_idx,
 	case TI_TSC2046_ADDR_AUX:
 	case TI_TSC2046_ADDR_VBAT:
 	case TI_TSC2046_ADDR_TEMP0:
-		pd |= TI_TSC2046_SER | TI_TSC2046_PD1_VREF_ON;
+		pd |= TI_TSC2046_SER;
+		if (!priv->vref_reg)
+			pd |= TI_TSC2046_PD1_VREF_ON;
 	}
 
 	return TI_TSC2046_START | FIELD_PREP(TI_TSC2046_ADDR, ch_idx) | pd;
@@ -468,7 +474,7 @@ static int tsc2046_adc_read_raw(struct iio_dev *indio_dev,
 		 * So, it is better to use external voltage-divider driver
 		 * instead, which is calculating complete chain.
 		 */
-		*val = TI_TSC2046_INT_VREF;
+		*val = priv->vref_mv;
 		*val2 = chan->scan_type.realbits;
 		return IIO_VAL_FRACTIONAL_LOG2;
 	}
@@ -740,6 +746,49 @@ static void tsc2046_adc_parse_fwnode(struct tsc2046_adc_priv *priv)
 	}
 }
 
+static void tsc2046_adc_regulator_disable(void *data)
+{
+	struct tsc2046_adc_priv *priv = data;
+
+	regulator_disable(priv->vref_reg);
+}
+
+static int tsc2046_adc_configure_regulator(struct tsc2046_adc_priv *priv)
+{
+	struct device *dev = &priv->spi->dev;
+	int ret;
+
+	priv->vref_reg = devm_regulator_get_optional(dev, "vref");
+	if (IS_ERR(priv->vref_reg)) {
+		/* If regulator exists but can't be get, return an error */
+		if (PTR_ERR(priv->vref_reg) != -ENODEV)
+			return PTR_ERR(priv->vref_reg);
+		priv->vref_reg = NULL;
+	}
+	if (!priv->vref_reg) {
+		/* Use internal reference */
+		priv->vref_mv = TI_TSC2046_INT_VREF;
+		return 0;
+	}
+
+	ret = regulator_enable(priv->vref_reg);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(dev, tsc2046_adc_regulator_disable,
+				       priv);
+	if (ret)
+		return ret;
+
+	ret = regulator_get_voltage(priv->vref_reg);
+	if (ret < 0)
+		return ret;
+
+	priv->vref_mv = ret / MILLI;
+
+	return 0;
+}
+
 static int tsc2046_adc_probe(struct spi_device *spi)
 {
 	const struct tsc2046_adc_dcfg *dcfg;
@@ -781,6 +830,10 @@ static int tsc2046_adc_probe(struct spi_device *spi)
 	indio_dev->num_channels = dcfg->num_channels;
 	indio_dev->info = &tsc2046_adc_info;
 
+	ret = tsc2046_adc_configure_regulator(priv);
+	if (ret)
+		return ret;
+
 	tsc2046_adc_parse_fwnode(priv);
 
 	ret = tsc2046_adc_setup_spi_msg(priv);
-- 
2.30.2