[PATCH v1 0/4] AD7949 Fixes

[PATCH v1 0/4] AD7949 Fixes

[Liam Beguin]

While working on another series[1] I ran into issues where my SPI
controller would fail to handle 14-bit and 16-bit SPI messages. This
addresses that issue and adds support for selecting a different voltage
reference source from the devicetree.

This is base on a series[2] that seems to not have made it all the way,
and was tested on an ad7689.

[1] https://patchwork.kernel.org/project/linux-iio/list/?series=511545
[2] https://patchwork.kernel.org/project/linux-iio/list/?series=116971&state=%2A&archive=both

Thanks for your time,
Liam

Liam Beguin (4):
  iio: adc: ad7949: define and use bitfield names
  iio: adc: ad7949: fix spi messages on non 14-bit controllers
  iio: adc: ad7949: add support for internal vref
  dt-bindings: iio: adc: ad7949: add adi,reference-source

 .../bindings/iio/adc/adi,ad7949.yaml          |  22 ++
 drivers/iio/adc/ad7949.c                      | 191 +++++++++++++++---
 2 files changed, 181 insertions(+), 32 deletions(-)


base-commit: 6cbb3aa0f9d5d23221df787cf36f74d3866fdb78
-- 
2.30.1.489.g328c10930387

[PATCH v1 1/4] iio: adc: ad7949: define and use bitfield names

[Liam Beguin]

From: Liam Beguin <lvb@xiphos.com>

Replace raw configuration register values by using FIELD_PREP and
defines to improve readability.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 drivers/iio/adc/ad7949.c | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index 1b4b3203e428..93aacf4f680b 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -12,12 +12,27 @@
 #include <linux/regulator/consumer.h>
 #include <linux/spi/spi.h>
 
-#define AD7949_MASK_CHANNEL_SEL		GENMASK(9, 7)
 #define AD7949_MASK_TOTAL		GENMASK(13, 0)
-#define AD7949_OFFSET_CHANNEL_SEL	7
-#define AD7949_CFG_READ_BACK		0x1
 #define AD7949_CFG_REG_SIZE_BITS	14
 
+#define AD7949_CFG_BIT_CFG		BIT(13)
+#define AD7949_CFG_VAL_CFG_OVERWRITE		1
+#define AD7949_CFG_VAL_CFG_KEEP			0
+#define AD7949_CFG_BIT_INCC		GENMASK(12, 10)
+#define AD7949_CFG_VAL_INCC_UNIPOLAR_GND	7
+#define AD7949_CFG_VAL_INCC_UNIPOLAR_COMM	6
+#define AD7949_CFG_VAL_INCC_UNIPOLAR_DIFF	4
+#define AD7949_CFG_VAL_INCC_TEMP		3
+#define AD7949_CFG_VAL_INCC_BIPOLAR		2
+#define AD7949_CFG_VAL_INCC_BIPOLAR_DIFF	0
+#define AD7949_CFG_BIT_INX		GENMASK(9, 7)
+#define AD7949_CFG_BIT_BW		BIT(6)
+#define AD7949_CFG_VAL_BW_FULL			1
+#define AD7949_CFG_VAL_BW_QUARTER		0
+#define AD7949_CFG_BIT_REF		GENMASK(5, 3)
+#define AD7949_CFG_BIT_SEQ		GENMASK(2, 1)
+#define AD7949_CFG_BIT_RBN		BIT(0)
+
 enum {
 	ID_AD7949 = 0,
 	ID_AD7682,
@@ -109,8 +124,8 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 	 */
 	for (i = 0; i < 2; i++) {
 		ret = ad7949_spi_write_cfg(ad7949_adc,
-					   channel << AD7949_OFFSET_CHANNEL_SEL,
-					   AD7949_MASK_CHANNEL_SEL);
+					   FIELD_PREP(AD7949_CFG_BIT_INX, channel),
+					   AD7949_CFG_BIT_INX);
 		if (ret)
 			return ret;
 		if (channel == ad7949_adc->current_channel)
@@ -214,10 +229,19 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
 {
 	int ret;
 	int val;
+	u16 cfg;
 
-	/* Sequencer disabled, CFG readback disabled, IN0 as default channel */
 	ad7949_adc->current_channel = 0;
-	ret = ad7949_spi_write_cfg(ad7949_adc, 0x3C79, AD7949_MASK_TOTAL);
+
+	cfg = FIELD_PREP(AD7949_CFG_BIT_CFG, AD7949_CFG_VAL_CFG_OVERWRITE) |
+		FIELD_PREP(AD7949_CFG_BIT_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
+		FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc->current_channel) |
+		FIELD_PREP(AD7949_CFG_BIT_BW, AD7949_CFG_VAL_BW_FULL) |
+		FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_REF_EXT_BUF) |
+		FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
+		FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
+
+	ret = ad7949_spi_write_cfg(ad7949_adc, cfg, AD7949_MASK_TOTAL);
 
 	/*
 	 * Do two dummy conversions to apply the first configuration setting.
-- 
2.30.1.489.g328c10930387

[PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bit controllers

[Liam Beguin]

From: Liam Beguin <lvb@xiphos.com>

This driver supports devices with 14-bit and 16-bit sample sizes.
This is not always handled properly by spi controllers and can fail. To
work around this limitation, pad samples to 16-bit and split the sample
into two 8-bit messages in the event that only 8-bit messages are
supported by the controller.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 drivers/iio/adc/ad7949.c | 67 ++++++++++++++++++++++++++++++++++------
 1 file changed, 58 insertions(+), 9 deletions(-)

diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index 93aacf4f680b..bbc6b56330a3 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/regulator/consumer.h>
 #include <linux/spi/spi.h>
+#include <linux/bitfield.h>
 
 #define AD7949_MASK_TOTAL		GENMASK(13, 0)
 #define AD7949_CFG_REG_SIZE_BITS	14
@@ -57,6 +58,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
  * @indio_dev: reference to iio structure
  * @spi: reference to spi structure
  * @resolution: resolution of the chip
+ * @bits_per_word: number of bits per SPI word
  * @cfg: copy of the configuration register
  * @current_channel: current channel in use
  * @buffer: buffer to send / receive data to / from device
@@ -67,28 +69,59 @@ struct ad7949_adc_chip {
 	struct iio_dev *indio_dev;
 	struct spi_device *spi;
 	u8 resolution;
+	u8 bits_per_word;
 	u16 cfg;
 	unsigned int current_channel;
-	u16 buffer ____cacheline_aligned;
+	union {
+		__be16 buffer;
+		u8 buf8[2];
+	} ____cacheline_aligned;
 };
 
+static void ad7949_set_bits_per_word(struct ad7949_adc_chip *ad7949_adc)
+{
+	u32 adc_mask = SPI_BPW_MASK(ad7949_adc->resolution);
+	u32 bpw = adc_mask & ad7949_adc->spi->controller->bits_per_word_mask;
+
+	if (bpw == adc_mask)
+		ad7949_adc->bits_per_word = ad7949_adc->resolution;
+	else if (bpw == SPI_BPW_MASK(16))
+		ad7949_adc->bits_per_word = 16;
+	else
+		ad7949_adc->bits_per_word = 8;
+}
+
 static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
 				u16 mask)
 {
 	int ret;
-	int bits_per_word = ad7949_adc->resolution;
-	int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
 	struct spi_message msg;
 	struct spi_transfer tx[] = {
 		{
 			.tx_buf = &ad7949_adc->buffer,
 			.len = 2,
-			.bits_per_word = bits_per_word,
+			.bits_per_word = ad7949_adc->bits_per_word,
 		},
 	};
 
+	ad7949_adc->buffer = 0;
 	ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
-	ad7949_adc->buffer = ad7949_adc->cfg << shift;
+
+	switch (ad7949_adc->bits_per_word) {
+	case 16:
+		ad7949_adc->buffer = ad7949_adc->cfg << 2;
+		break;
+	case 14:
+		ad7949_adc->buffer = ad7949_adc->cfg;
+		break;
+	case 8:
+		/* Pack 14-bit value into 2 bytes, MSB first */
+		ad7949_adc->buf8[0] = FIELD_GET(GENMASK(13, 6), ad7949_adc->cfg);
+		ad7949_adc->buf8[1] = FIELD_GET(GENMASK(5, 0), ad7949_adc->cfg);
+		ad7949_adc->buf8[1] = ad7949_adc->buf8[1] << 2;
+		break;
+	}
+
 	spi_message_init_with_transfers(&msg, tx, 1);
 	ret = spi_sync(ad7949_adc->spi, &msg);
 
@@ -105,14 +138,12 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 {
 	int ret;
 	int i;
-	int bits_per_word = ad7949_adc->resolution;
-	int mask = GENMASK(ad7949_adc->resolution - 1, 0);
 	struct spi_message msg;
 	struct spi_transfer tx[] = {
 		{
 			.rx_buf = &ad7949_adc->buffer,
 			.len = 2,
-			.bits_per_word = bits_per_word,
+			.bits_per_word = ad7949_adc->bits_per_word,
 		},
 	};
 
@@ -147,7 +178,24 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 
 	ad7949_adc->current_channel = channel;
 
-	*val = ad7949_adc->buffer & mask;
+	switch (ad7949_adc->bits_per_word) {
+	case 16:
+		*val = ad7949_adc->buffer;
+		/* Shift-out padding bits */
+		if (ad7949_adc->resolution == 14)
+			*val = *val >> 2;
+		break;
+	case 14:
+		*val = ad7949_adc->buffer & GENMASK(13, 0);
+		break;
+	case 8:
+		/* Convert byte array to u16, MSB first */
+		*val = (ad7949_adc->buf8[0] << 8) | ad7949_adc->buf8[1];
+		/* Shift-out padding bits */
+		if (ad7949_adc->resolution == 14)
+			*val = *val >> 2;
+		break;
+	}
 
 	return 0;
 }
@@ -280,6 +328,7 @@ static int ad7949_spi_probe(struct spi_device *spi)
 	spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
 	indio_dev->num_channels = spec->num_channels;
 	ad7949_adc->resolution = spec->resolution;
+	ad7949_set_bits_per_word(ad7949_adc);
 
 	ad7949_adc->vref = devm_regulator_get(dev, "vref");
 	if (IS_ERR(ad7949_adc->vref)) {
-- 
2.30.1.489.g328c10930387

[PATCH v1 3/4] iio: adc: ad7949: add support for internal vref

[Liam Beguin]

From: Liam Beguin <lvb@xiphos.com>

Add support for selecting a custom reference voltage from the
devicetree. If an external source is used, a vref regulator should be
defined in the devicetree.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 drivers/iio/adc/ad7949.c | 84 +++++++++++++++++++++++++++++++++-------
 1 file changed, 69 insertions(+), 15 deletions(-)

diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index bbc6b56330a3..3c1293922d2e 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -31,6 +31,7 @@
 #define AD7949_CFG_VAL_BW_FULL			1
 #define AD7949_CFG_VAL_BW_QUARTER		0
 #define AD7949_CFG_BIT_REF		GENMASK(5, 3)
+#define AD7949_CFG_VAL_REF_EXTERNAL		BIT(1)
 #define AD7949_CFG_BIT_SEQ		GENMASK(2, 1)
 #define AD7949_CFG_BIT_RBN		BIT(0)
 
@@ -40,6 +41,33 @@ enum {
 	ID_AD7689,
 };
 
+/**
+ * enum ad7949_ref - Reference selection
+ *
+ * AD7949_REF_INT_2500:     Internal reference and temperature sensor enabled.
+ *                          Vref=2.5V, buffered output
+ * AD7949_REF_INT_4096:     Internal reference and temperature sensor enabled.
+ *                          Vref=4.096V, buffered output
+ * AD7949_REF_EXT_TEMP:     Use external reference, temperature sensor enabled.
+ *                          Internal buffer disabled
+ * AD7949_REF_EXT_TEMP_BUF: Use external reference, internal buffer and
+ *                          temperature sensor enabled.
+ * AD7949_REF_RSRV_4:       Do not use
+ * AD7949_REF_RSRV_5:       Do not use
+ * AD7949_REF_EXT:          Use external reference, internal buffer and
+ *                          temperature sensor disabled.
+ * AD7949_REF_EXT_BUF:      Use external reference, internal buffer enabled.
+ *                          Internal reference and temperature sensor disabled.
+ */
+enum ad7949_ref {
+	AD7949_REF_INT_2500 = 0,
+	AD7949_REF_INT_4096,
+	AD7949_REF_EXT_TEMP,
+	AD7949_REF_EXT_TEMP_BUF,
+	AD7949_REF_EXT = 6,
+	AD7949_REF_EXT_BUF,
+};
+
 struct ad7949_adc_spec {
 	u8 num_channels;
 	u8 resolution;
@@ -55,6 +83,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
  * struct ad7949_adc_chip - AD ADC chip
  * @lock: protects write sequences
  * @vref: regulator generating Vref
+ * @refsel: reference selection
  * @indio_dev: reference to iio structure
  * @spi: reference to spi structure
  * @resolution: resolution of the chip
@@ -66,6 +95,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
 struct ad7949_adc_chip {
 	struct mutex lock;
 	struct regulator *vref;
+	enum ad7949_ref refsel;
 	struct iio_dev *indio_dev;
 	struct spi_device *spi;
 	u8 resolution;
@@ -241,12 +271,28 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_SCALE:
-		ret = regulator_get_voltage(ad7949_adc->vref);
-		if (ret < 0)
-			return ret;
+		switch (ad7949_adc->refsel) {
+		case AD7949_REF_INT_2500:
+			*val = 2500;
+			break;
+		case AD7949_REF_INT_4096:
+			*val = 4096;
+			break;
+		case AD7949_REF_EXT_TEMP:
+		case AD7949_REF_EXT_TEMP_BUF:
+		case AD7949_REF_EXT:
+		case AD7949_REF_EXT_BUF:
+			ret = regulator_get_voltage(ad7949_adc->vref);
+			if (ret < 0)
+				return ret;
+
+			/* convert value back to mV */
+			*val = ret / 1000;
+			break;
+		}
 
-		*val = ret / 5000;
-		return IIO_VAL_INT;
+		*val2 = (1 << ad7949_adc->resolution) - 1;
+		return IIO_VAL_FRACTIONAL;
 	}
 
 	return -EINVAL;
@@ -285,7 +331,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
 		FIELD_PREP(AD7949_CFG_BIT_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
 		FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc->current_channel) |
 		FIELD_PREP(AD7949_CFG_BIT_BW, AD7949_CFG_VAL_BW_FULL) |
-		FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_REF_EXT_BUF) |
+		FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc->refsel) |
 		FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
 		FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
 
@@ -304,6 +350,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
 static int ad7949_spi_probe(struct spi_device *spi)
 {
 	struct device *dev = &spi->dev;
+	struct device_node *np = dev->of_node;
 	const struct ad7949_adc_spec *spec;
 	struct ad7949_adc_chip *ad7949_adc;
 	struct iio_dev *indio_dev;
@@ -315,6 +362,7 @@ static int ad7949_spi_probe(struct spi_device *spi)
 		return -ENOMEM;
 	}
 
+	indio_dev->dev.of_node = np;
 	indio_dev->info = &ad7949_spi_info;
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
@@ -330,16 +378,22 @@ static int ad7949_spi_probe(struct spi_device *spi)
 	ad7949_adc->resolution = spec->resolution;
 	ad7949_set_bits_per_word(ad7949_adc);
 
-	ad7949_adc->vref = devm_regulator_get(dev, "vref");
-	if (IS_ERR(ad7949_adc->vref)) {
-		dev_err(dev, "fail to request regulator\n");
-		return PTR_ERR(ad7949_adc->vref);
-	}
+	/* Set default devicetree parameters */
+	ad7949_adc->refsel = AD7949_REF_EXT_BUF;
+	of_property_read_u32(np, "adi,reference-select", &ad7949_adc->refsel);
 
-	ret = regulator_enable(ad7949_adc->vref);
-	if (ret < 0) {
-		dev_err(dev, "fail to enable regulator\n");
-		return ret;
+	if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
+		ad7949_adc->vref = devm_regulator_get(dev, "vref");
+		if (IS_ERR(ad7949_adc->vref)) {
+			dev_err(dev, "fail to request regulator\n");
+			return PTR_ERR(ad7949_adc->vref);
+		}
+
+		ret = regulator_enable(ad7949_adc->vref);
+		if (ret < 0) {
+			dev_err(dev, "fail to enable regulator\n");
+			return ret;
+		}
 	}
 
 	mutex_init(&ad7949_adc->lock);
-- 
2.30.1.489.g328c10930387

[PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add adi,reference-source

[Liam Beguin]

From: Liam Beguin <lvb@xiphos.com>

Add bindings documentation for the adi,reference-source property.
This property is required to properly configure the ADC sample request
based on which reference source should be used for the calculation.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 .../bindings/iio/adc/adi,ad7949.yaml          | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
index 9b56bd4d5510..3f4629281cc8 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
@@ -35,6 +35,28 @@ properties:
   "#io-channel-cells":
     const: 1
 
+  adi,reference-select:
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - enum: [0, 1, 2, 3, 6, 7]
+
+    default: 7
+    description: |
+      Select the reference voltage source to use when converting samples.
+      Acceptable values are:
+      - 0: Internal reference and temperature sensor enabled.
+           Vref=2.5V, buffered output
+      - 1: Internal reference and temperature sensor enabled.
+           Vref=4.096V, buffered output
+      - 2: Use external reference, temperature sensor enabled.
+           Internal buffer disabled
+      - 3: Use external reference, internal buffer and temperature sensor
+           enabled.
+      - 6: Use external reference, internal buffer and temperature sensor
+           disabled.
+      - 7: Use external reference, internal buffer enabled.
+           Internal reference and temperature sensor disabled.
+
 required:
   - compatible
   - reg
-- 
2.30.1.489.g328c10930387

RE: [PATCH v1 0/4] AD7949 Fixes

[Sa, Nuno]

Hi Liam,

The series looks good. Just some minor comments from my side...

Thanks!
- Nuno Sá

> From: Liam Beguin <liambeguin@gmail.com>
> Sent: Friday, July 9, 2021 1:56 AM
> To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> antoine.couret@essensium.com
> Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> devicetree@vger.kernel.org; robh+dt@kernel.org
> Subject: [PATCH v1 0/4] AD7949 Fixes
> 
> [External]
> 
> While working on another series[1] I ran into issues where my SPI
> controller would fail to handle 14-bit and 16-bit SPI messages. This
> addresses that issue and adds support for selecting a different voltage
> reference source from the devicetree.
> 
> This is base on a series[2] that seems to not have made it all the way,
> and was tested on an ad7689.
> 
> [1]
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/li
> nux-iio/list/?series=511545__;!!A3Ni8CS0y2Y!rF7O-WxC7HZM4hv_o-
> zYPtVCmZlDoASzPvamwwQkH9llVS8J-GpfQltvDBz7gQ$
> [2]
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/li
> nux-
> iio/list/?series=116971&state=*2A&archive=both__;JQ!!A3Ni8CS0y2Y!
> rF7O-WxC7HZM4hv_o-zYPtVCmZlDoASzPvamwwQkH9llVS8J-GpfQluZ-
> w3LYA$
> 
> Thanks for your time,
> Liam
> 
> Liam Beguin (4):
>   iio: adc: ad7949: define and use bitfield names
>   iio: adc: ad7949: fix spi messages on non 14-bit controllers
>   iio: adc: ad7949: add support for internal vref
>   dt-bindings: iio: adc: ad7949: add adi,reference-source
> 
>  .../bindings/iio/adc/adi,ad7949.yaml          |  22 ++
>  drivers/iio/adc/ad7949.c                      | 191 +++++++++++++++---
>  2 files changed, 181 insertions(+), 32 deletions(-)
> 
> 
> base-commit: 6cbb3aa0f9d5d23221df787cf36f74d3866fdb78
> --
> 2.30.1.489.g328c10930387

RE: [PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add adi,reference-source

[Sa, Nuno]

> -----Original Message-----
> From: Liam Beguin <liambeguin@gmail.com>
> Sent: Friday, July 9, 2021 1:56 AM
> To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> antoine.couret@essensium.com
> Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> devicetree@vger.kernel.org; robh+dt@kernel.org
> Subject: [PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add
> adi,reference-source
> 
> [External]
> 
> From: Liam Beguin <lvb@xiphos.com>
> 
> Add bindings documentation for the adi,reference-source property.
> This property is required to properly configure the ADC sample request
> based on which reference source should be used for the calculation.
> 
> Signed-off-by: Liam Beguin <lvb@xiphos.com>
> ---
>  .../bindings/iio/adc/adi,ad7949.yaml          | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git
> a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> index 9b56bd4d5510..3f4629281cc8 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> @@ -35,6 +35,28 @@ properties:
>    "#io-channel-cells":
>      const: 1
> 
> +  adi,reference-select:
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +      - enum: [0, 1, 2, 3, 6, 7]
> +
> +    default: 7
> +    description: |
> +      Select the reference voltage source to use when converting
> samples.
> +      Acceptable values are:
> +      - 0: Internal reference and temperature sensor enabled.
> +           Vref=2.5V, buffered output
> +      - 1: Internal reference and temperature sensor enabled.
> +           Vref=4.096V, buffered output
> +      - 2: Use external reference, temperature sensor enabled.
> +           Internal buffer disabled
> +      - 3: Use external reference, internal buffer and temperature
> sensor
> +           enabled.
> +      - 6: Use external reference, internal buffer and temperature
> sensor
> +           disabled.
> +      - 7: Use external reference, internal buffer enabled.
> +           Internal reference and temperature sensor disabled.

I think typically the description comes first. I also don't think you
need the 'allOf'(not even sure if it will pass the binding check)...
Just have '$ref' and 'enum' on the same level.

- Nuno Sá

>  required:
>    - compatible
>    - reg
> --
> 2.30.1.489.g328c10930387

RE: [PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bit controllers

[Sa, Nuno]

> -----Original Message-----
> From: Liam Beguin <liambeguin@gmail.com>
> Sent: Friday, July 9, 2021 1:56 AM
> To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> antoine.couret@essensium.com
> Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> devicetree@vger.kernel.org; robh+dt@kernel.org
> Subject: [PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bit
> controllers
> 
> [External]
> 
> From: Liam Beguin <lvb@xiphos.com>
> 
> This driver supports devices with 14-bit and 16-bit sample sizes.
> This is not always handled properly by spi controllers and can fail. To
> work around this limitation, pad samples to 16-bit and split the sample
> into two 8-bit messages in the event that only 8-bit messages are
> supported by the controller.
> 
> Signed-off-by: Liam Beguin <lvb@xiphos.com>
> ---
>  drivers/iio/adc/ad7949.c | 67
> ++++++++++++++++++++++++++++++++++------
>  1 file changed, 58 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index 93aacf4f680b..bbc6b56330a3 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -11,6 +11,7 @@
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/spi/spi.h>
> +#include <linux/bitfield.h>
> 
>  #define AD7949_MASK_TOTAL		GENMASK(13, 0)
>  #define AD7949_CFG_REG_SIZE_BITS	14
> @@ -57,6 +58,7 @@ static const struct ad7949_adc_spec
> ad7949_adc_spec[] = {
>   * @indio_dev: reference to iio structure
>   * @spi: reference to spi structure
>   * @resolution: resolution of the chip
> + * @bits_per_word: number of bits per SPI word
>   * @cfg: copy of the configuration register
>   * @current_channel: current channel in use
>   * @buffer: buffer to send / receive data to / from device
> @@ -67,28 +69,59 @@ struct ad7949_adc_chip {
>  	struct iio_dev *indio_dev;
>  	struct spi_device *spi;
>  	u8 resolution;
> +	u8 bits_per_word;
>  	u16 cfg;
>  	unsigned int current_channel;
> -	u16 buffer ____cacheline_aligned;
> +	union {
> +		__be16 buffer;
> +		u8 buf8[2];
> +	} ____cacheline_aligned;
>  };
> 
> +static void ad7949_set_bits_per_word(struct ad7949_adc_chip
> *ad7949_adc)
> +{
> +	u32 adc_mask = SPI_BPW_MASK(ad7949_adc->resolution);
> +	u32 bpw = adc_mask & ad7949_adc->spi->controller-
> >bits_per_word_mask;
> +
> +	if (bpw == adc_mask)
> +		ad7949_adc->bits_per_word = ad7949_adc-
> >resolution;
> +	else if (bpw == SPI_BPW_MASK(16))
> +		ad7949_adc->bits_per_word = 16;
> +	else
> +		ad7949_adc->bits_per_word = 8;
> +}
> +
>  static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc,
> u16 val,
>  				u16 mask)
>  {
>  	int ret;
> -	int bits_per_word = ad7949_adc->resolution;
> -	int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
>  	struct spi_message msg;
>  	struct spi_transfer tx[] = {
>  		{
>  			.tx_buf = &ad7949_adc->buffer,
>  			.len = 2,
> -			.bits_per_word = bits_per_word,
> +			.bits_per_word = ad7949_adc->bits_per_word,
>  		},
>  	};
> 
> +	ad7949_adc->buffer = 0;
>  	ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
> -	ad7949_adc->buffer = ad7949_adc->cfg << shift;
> +
> +	switch (ad7949_adc->bits_per_word) {
> +	case 16:
> +		ad7949_adc->buffer = ad7949_adc->cfg << 2;
> +		break;
> +	case 14:
> +		ad7949_adc->buffer = ad7949_adc->cfg;
> +		break;
> +	case 8:
> +		/* Pack 14-bit value into 2 bytes, MSB first */
> +		ad7949_adc->buf8[0] = FIELD_GET(GENMASK(13, 6),
> ad7949_adc->cfg);
> +		ad7949_adc->buf8[1] = FIELD_GET(GENMASK(5, 0),
> ad7949_adc->cfg);
> +		ad7949_adc->buf8[1] = ad7949_adc->buf8[1] << 2;
> +		break;
> +	}

Honestly I didn't went through the driver but just a question... Are we
sure that 'ad7949_adc->resolution' will have something valid (8, 14, 16)?
A default statement is always a nice to have :).
 
>  	spi_message_init_with_transfers(&msg, tx, 1);
>  	ret = spi_sync(ad7949_adc->spi, &msg);
> 
> @@ -105,14 +138,12 @@ static int ad7949_spi_read_channel(struct
> ad7949_adc_chip *ad7949_adc, int *val,
>  {
>  	int ret;
>  	int i;
> -	int bits_per_word = ad7949_adc->resolution;
> -	int mask = GENMASK(ad7949_adc->resolution - 1, 0);
>  	struct spi_message msg;
>  	struct spi_transfer tx[] = {
>  		{
>  			.rx_buf = &ad7949_adc->buffer,
>  			.len = 2,
> -			.bits_per_word = bits_per_word,
> +			.bits_per_word = ad7949_adc->bits_per_word,
>  		},
>  	};
> 
> @@ -147,7 +178,24 @@ static int ad7949_spi_read_channel(struct
> ad7949_adc_chip *ad7949_adc, int *val,
> 
>  	ad7949_adc->current_channel = channel;
> 
> -	*val = ad7949_adc->buffer & mask;
> +	switch (ad7949_adc->bits_per_word) {
> +	case 16:
> +		*val = ad7949_adc->buffer;
> +		/* Shift-out padding bits */
> +		if (ad7949_adc->resolution == 14)
> +			*val = *val >> 2;
> +		break;
> +	case 14:
> +		*val = ad7949_adc->buffer & GENMASK(13, 0);
> +		break;
> +	case 8:
> +		/* Convert byte array to u16, MSB first */
> +		*val = (ad7949_adc->buf8[0] << 8) | ad7949_adc-
> >buf8[1];
> +		/* Shift-out padding bits */
> +		if (ad7949_adc->resolution == 14)
> +			*val = *val >> 2;
> +		break;
> +	}
> 
>  	return 0;
>  }
> @@ -280,6 +328,7 @@ static int ad7949_spi_probe(struct spi_device
> *spi)
>  	spec = &ad7949_adc_spec[spi_get_device_id(spi)-
> >driver_data];
>  	indio_dev->num_channels = spec->num_channels;
>  	ad7949_adc->resolution = spec->resolution;
> +	ad7949_set_bits_per_word(ad7949_adc);
> 
>  	ad7949_adc->vref = devm_regulator_get(dev, "vref");
>  	if (IS_ERR(ad7949_adc->vref)) {
> --
> 2.30.1.489.g328c10930387

RE: [PATCH v1 3/4] iio: adc: ad7949: add support for internal vref

[Sa, Nuno]

> From: Liam Beguin <liambeguin@gmail.com>
> Sent: Friday, July 9, 2021 1:56 AM
> To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> antoine.couret@essensium.com
> Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> devicetree@vger.kernel.org; robh+dt@kernel.org
> Subject: [PATCH v1 3/4] iio: adc: ad7949: add support for internal vref
> 
> [External]
> 
> From: Liam Beguin <lvb@xiphos.com>
> 
> Add support for selecting a custom reference voltage from the
> devicetree. If an external source is used, a vref regulator should be
> defined in the devicetree.
> 
> Signed-off-by: Liam Beguin <lvb@xiphos.com>
> ---
>  drivers/iio/adc/ad7949.c | 84
> +++++++++++++++++++++++++++++++++-------
>  1 file changed, 69 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index bbc6b56330a3..3c1293922d2e 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -31,6 +31,7 @@
>  #define AD7949_CFG_VAL_BW_FULL			1
>  #define AD7949_CFG_VAL_BW_QUARTER		0
>  #define AD7949_CFG_BIT_REF		GENMASK(5, 3)
> +#define AD7949_CFG_VAL_REF_EXTERNAL		BIT(1)
>  #define AD7949_CFG_BIT_SEQ		GENMASK(2, 1)
>  #define AD7949_CFG_BIT_RBN		BIT(0)
> 
> @@ -40,6 +41,33 @@ enum {
>  	ID_AD7689,
>  };
> 
> +/**
> + * enum ad7949_ref - Reference selection
> + *
> + * AD7949_REF_INT_2500:     Internal reference and temperature
> sensor enabled.
> + *                          Vref=2.5V, buffered output
> + * AD7949_REF_INT_4096:     Internal reference and temperature
> sensor enabled.
> + *                          Vref=4.096V, buffered output
> + * AD7949_REF_EXT_TEMP:     Use external reference, temperature
> sensor enabled.
> + *                          Internal buffer disabled
> + * AD7949_REF_EXT_TEMP_BUF: Use external reference, internal
> buffer and
> + *                          temperature sensor enabled.
> + * AD7949_REF_RSRV_4:       Do not use
> + * AD7949_REF_RSRV_5:       Do not use
> + * AD7949_REF_EXT:          Use external reference, internal buffer and
> + *                          temperature sensor disabled.
> + * AD7949_REF_EXT_BUF:      Use external reference, internal buffer
> enabled.
> + *                          Internal reference and temperature sensor disabled.
> + */
> +enum ad7949_ref {
> +	AD7949_REF_INT_2500 = 0,
> +	AD7949_REF_INT_4096,
> +	AD7949_REF_EXT_TEMP,
> +	AD7949_REF_EXT_TEMP_BUF,
> +	AD7949_REF_EXT = 6,
> +	AD7949_REF_EXT_BUF,
> +};
> +
>  struct ad7949_adc_spec {
>  	u8 num_channels;
>  	u8 resolution;
> @@ -55,6 +83,7 @@ static const struct ad7949_adc_spec
> ad7949_adc_spec[] = {
>   * struct ad7949_adc_chip - AD ADC chip
>   * @lock: protects write sequences
>   * @vref: regulator generating Vref
> + * @refsel: reference selection
>   * @indio_dev: reference to iio structure
>   * @spi: reference to spi structure
>   * @resolution: resolution of the chip
> @@ -66,6 +95,7 @@ static const struct ad7949_adc_spec
> ad7949_adc_spec[] = {
>  struct ad7949_adc_chip {
>  	struct mutex lock;
>  	struct regulator *vref;
> +	enum ad7949_ref refsel;
>  	struct iio_dev *indio_dev;
>  	struct spi_device *spi;
>  	u8 resolution;
> @@ -241,12 +271,28 @@ static int ad7949_spi_read_raw(struct iio_dev
> *indio_dev,
>  		return IIO_VAL_INT;
> 
>  	case IIO_CHAN_INFO_SCALE:
> -		ret = regulator_get_voltage(ad7949_adc->vref);
> -		if (ret < 0)
> -			return ret;
> +		switch (ad7949_adc->refsel) {
> +		case AD7949_REF_INT_2500:
> +			*val = 2500;
> +			break;
> +		case AD7949_REF_INT_4096:
> +			*val = 4096;
> +			break;
> +		case AD7949_REF_EXT_TEMP:
> +		case AD7949_REF_EXT_TEMP_BUF:
> +		case AD7949_REF_EXT:
> +		case AD7949_REF_EXT_BUF:
> +			ret = regulator_get_voltage(ad7949_adc-
> >vref);
> +			if (ret < 0)
> +				return ret;
> +
> +			/* convert value back to mV */
> +			*val = ret / 1000;
> +			break;
> +		}
> 
> -		*val = ret / 5000;
> -		return IIO_VAL_INT;
> +		*val2 = (1 << ad7949_adc->resolution) - 1;
> +		return IIO_VAL_FRACTIONAL;
>  	}
> 
>  	return -EINVAL;
> @@ -285,7 +331,7 @@ static int ad7949_spi_init(struct
> ad7949_adc_chip *ad7949_adc)
>  		FIELD_PREP(AD7949_CFG_BIT_INCC,
> AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
>  		FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc-
> >current_channel) |
>  		FIELD_PREP(AD7949_CFG_BIT_BW,
> AD7949_CFG_VAL_BW_FULL) |
> -		FIELD_PREP(AD7949_CFG_BIT_REF,
> AD7949_REF_EXT_BUF) |
> +		FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc-
> >refsel) |
>  		FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
>  		FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
> 
> @@ -304,6 +350,7 @@ static int ad7949_spi_init(struct
> ad7949_adc_chip *ad7949_adc)
>  static int ad7949_spi_probe(struct spi_device *spi)
>  {
>  	struct device *dev = &spi->dev;
> +	struct device_node *np = dev->of_node;
>  	const struct ad7949_adc_spec *spec;
>  	struct ad7949_adc_chip *ad7949_adc;
>  	struct iio_dev *indio_dev;
> @@ -315,6 +362,7 @@ static int ad7949_spi_probe(struct spi_device
> *spi)
>  		return -ENOMEM;
>  	}
> 
> +	indio_dev->dev.of_node = np;

Why doing this? The IIO core will do it for us at register time.

>  	indio_dev->info = &ad7949_spi_info;
>  	indio_dev->name = spi_get_device_id(spi)->name;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
> @@ -330,16 +378,22 @@ static int ad7949_spi_probe(struct spi_device
> *spi)
>  	ad7949_adc->resolution = spec->resolution;
>  	ad7949_set_bits_per_word(ad7949_adc);
> 
> -	ad7949_adc->vref = devm_regulator_get(dev, "vref");
> -	if (IS_ERR(ad7949_adc->vref)) {
> -		dev_err(dev, "fail to request regulator\n");
> -		return PTR_ERR(ad7949_adc->vref);
> -	}
> +	/* Set default devicetree parameters */
> +	ad7949_adc->refsel = AD7949_REF_EXT_BUF;
> +	of_property_read_u32(np, "adi,reference-select",
> &ad7949_adc->refsel);

In case the property is given, we should make sure we get a valid
value and error out if not...

- Nuno Sá
> -	ret = regulator_enable(ad7949_adc->vref);
> -	if (ret < 0) {
> -		dev_err(dev, "fail to enable regulator\n");
> -		return ret;
> +	if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
> +		ad7949_adc->vref = devm_regulator_get(dev, "vref");
> +		if (IS_ERR(ad7949_adc->vref)) {
> +			dev_err(dev, "fail to request regulator\n");
> +			return PTR_ERR(ad7949_adc->vref);
> +		}
> +
> +		ret = regulator_enable(ad7949_adc->vref);
> +		if (ret < 0) {
> +			dev_err(dev, "fail to enable regulator\n");
> +			return ret;
> +		}
>  	}
> 
>  	mutex_init(&ad7949_adc->lock);
> --
> 2.30.1.489.g328c10930387

RE: [PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add adi,reference-source

[Liam Beguin]

Hi Nuno,

On Fri Jul 9, 2021 at 4:15 AM EDT, Sa, Nuno wrote:
>
>
> > -----Original Message-----
> > From: Liam Beguin <liambeguin@gmail.com>
> > Sent: Friday, July 9, 2021 1:56 AM
> > To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> > <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> > antoine.couret@essensium.com
> > Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> > devicetree@vger.kernel.org; robh+dt@kernel.org
> > Subject: [PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add
> > adi,reference-source
> > 
> > [External]
> > 
> > From: Liam Beguin <lvb@xiphos.com>
> > 
> > Add bindings documentation for the adi,reference-source property.
> > This property is required to properly configure the ADC sample request
> > based on which reference source should be used for the calculation.
> > 
> > Signed-off-by: Liam Beguin <lvb@xiphos.com>
> > ---
> >  .../bindings/iio/adc/adi,ad7949.yaml          | 22 +++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > index 9b56bd4d5510..3f4629281cc8 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > @@ -35,6 +35,28 @@ properties:
> >    "#io-channel-cells":
> >      const: 1
> > 
> > +  adi,reference-select:
> > +    allOf:
> > +      - $ref: /schemas/types.yaml#/definitions/uint32
> > +      - enum: [0, 1, 2, 3, 6, 7]
> > +
> > +    default: 7
> > +    description: |
> > +      Select the reference voltage source to use when converting
> > samples.
> > +      Acceptable values are:
> > +      - 0: Internal reference and temperature sensor enabled.
> > +           Vref=2.5V, buffered output
> > +      - 1: Internal reference and temperature sensor enabled.
> > +           Vref=4.096V, buffered output
> > +      - 2: Use external reference, temperature sensor enabled.
> > +           Internal buffer disabled
> > +      - 3: Use external reference, internal buffer and temperature
> > sensor
> > +           enabled.
> > +      - 6: Use external reference, internal buffer and temperature
> > sensor
> > +           disabled.
> > +      - 7: Use external reference, internal buffer enabled.
> > +           Internal reference and temperature sensor disabled.
>
> I think typically the description comes first. I also don't think you
> need the 'allOf'(not even sure if it will pass the binding check)...
> Just have '$ref' and 'enum' on the same level.
>

Understood, I can reorder the patches so that the bindings come first.

I thought I based that part on the `example-schema.yaml`, but looking at
it again, it seems like you're right and the AllOf isn't required.

I did run the bindings check on this, but I'll fix it.

Thanks,
Liam

> - Nuno Sá
>
> >  required:
> >    - compatible
> >    - reg
> > --
> > 2.30.1.489.g328c10930387

RE: [PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bit controllers

[Liam Beguin]

On Fri Jul 9, 2021 at 4:19 AM EDT, Sa, Nuno wrote:
>
>
> > -----Original Message-----
> > From: Liam Beguin <liambeguin@gmail.com>
> > Sent: Friday, July 9, 2021 1:56 AM
> > To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> > <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> > antoine.couret@essensium.com
> > Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> > devicetree@vger.kernel.org; robh+dt@kernel.org
> > Subject: [PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bit
> > controllers
> > 
> > [External]
> > 
> > From: Liam Beguin <lvb@xiphos.com>
> > 
> > This driver supports devices with 14-bit and 16-bit sample sizes.
> > This is not always handled properly by spi controllers and can fail. To
> > work around this limitation, pad samples to 16-bit and split the sample
> > into two 8-bit messages in the event that only 8-bit messages are
> > supported by the controller.
> > 
> > Signed-off-by: Liam Beguin <lvb@xiphos.com>
> > ---
> >  drivers/iio/adc/ad7949.c | 67
> > ++++++++++++++++++++++++++++++++++------
> >  1 file changed, 58 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > index 93aacf4f680b..bbc6b56330a3 100644
> > --- a/drivers/iio/adc/ad7949.c
> > +++ b/drivers/iio/adc/ad7949.c
> > @@ -11,6 +11,7 @@
> >  #include <linux/module.h>
> >  #include <linux/regulator/consumer.h>
> >  #include <linux/spi/spi.h>
> > +#include <linux/bitfield.h>
> > 
> >  #define AD7949_MASK_TOTAL		GENMASK(13, 0)
> >  #define AD7949_CFG_REG_SIZE_BITS	14
> > @@ -57,6 +58,7 @@ static const struct ad7949_adc_spec
> > ad7949_adc_spec[] = {
> >   * @indio_dev: reference to iio structure
> >   * @spi: reference to spi structure
> >   * @resolution: resolution of the chip
> > + * @bits_per_word: number of bits per SPI word
> >   * @cfg: copy of the configuration register
> >   * @current_channel: current channel in use
> >   * @buffer: buffer to send / receive data to / from device
> > @@ -67,28 +69,59 @@ struct ad7949_adc_chip {
> >  	struct iio_dev *indio_dev;
> >  	struct spi_device *spi;
> >  	u8 resolution;
> > +	u8 bits_per_word;
> >  	u16 cfg;
> >  	unsigned int current_channel;
> > -	u16 buffer ____cacheline_aligned;
> > +	union {
> > +		__be16 buffer;
> > +		u8 buf8[2];
> > +	} ____cacheline_aligned;
> >  };
> > 
> > +static void ad7949_set_bits_per_word(struct ad7949_adc_chip
> > *ad7949_adc)
> > +{
> > +	u32 adc_mask = SPI_BPW_MASK(ad7949_adc->resolution);
> > +	u32 bpw = adc_mask & ad7949_adc->spi->controller-
> > >bits_per_word_mask;
> > +
> > +	if (bpw == adc_mask)
> > +		ad7949_adc->bits_per_word = ad7949_adc-
> > >resolution;
> > +	else if (bpw == SPI_BPW_MASK(16))
> > +		ad7949_adc->bits_per_word = 16;
> > +	else
> > +		ad7949_adc->bits_per_word = 8;
> > +}
> > +
> >  static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc,
> > u16 val,
> >  				u16 mask)
> >  {
> >  	int ret;
> > -	int bits_per_word = ad7949_adc->resolution;
> > -	int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
> >  	struct spi_message msg;
> >  	struct spi_transfer tx[] = {
> >  		{
> >  			.tx_buf = &ad7949_adc->buffer,
> >  			.len = 2,
> > -			.bits_per_word = bits_per_word,
> > +			.bits_per_word = ad7949_adc->bits_per_word,
> >  		},
> >  	};
> > 
> > +	ad7949_adc->buffer = 0;
> >  	ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
> > -	ad7949_adc->buffer = ad7949_adc->cfg << shift;
> > +
> > +	switch (ad7949_adc->bits_per_word) {
> > +	case 16:
> > +		ad7949_adc->buffer = ad7949_adc->cfg << 2;
> > +		break;
> > +	case 14:
> > +		ad7949_adc->buffer = ad7949_adc->cfg;
> > +		break;
> > +	case 8:
> > +		/* Pack 14-bit value into 2 bytes, MSB first */
> > +		ad7949_adc->buf8[0] = FIELD_GET(GENMASK(13, 6),
> > ad7949_adc->cfg);
> > +		ad7949_adc->buf8[1] = FIELD_GET(GENMASK(5, 0),
> > ad7949_adc->cfg);
> > +		ad7949_adc->buf8[1] = ad7949_adc->buf8[1] << 2;
> > +		break;
> > +	}
>
> Honestly I didn't went through the driver but just a question... Are we
> sure that 'ad7949_adc->resolution' will have something valid (8, 14,
> 16)?
> A default statement is always a nice to have :).
>  

Thanks for pointing that out. You're right that based on this driver
there's no guaranty that `ad7949_adc->resolution` will have a valid
value. I'll add a default to 8-bit.

Thanks,
Liam

> >  	spi_message_init_with_transfers(&msg, tx, 1);
> >  	ret = spi_sync(ad7949_adc->spi, &msg);
> > 
> > @@ -105,14 +138,12 @@ static int ad7949_spi_read_channel(struct
> > ad7949_adc_chip *ad7949_adc, int *val,
> >  {
> >  	int ret;
> >  	int i;
> > -	int bits_per_word = ad7949_adc->resolution;
> > -	int mask = GENMASK(ad7949_adc->resolution - 1, 0);
> >  	struct spi_message msg;
> >  	struct spi_transfer tx[] = {
> >  		{
> >  			.rx_buf = &ad7949_adc->buffer,
> >  			.len = 2,
> > -			.bits_per_word = bits_per_word,
> > +			.bits_per_word = ad7949_adc->bits_per_word,
> >  		},
> >  	};
> > 
> > @@ -147,7 +178,24 @@ static int ad7949_spi_read_channel(struct
> > ad7949_adc_chip *ad7949_adc, int *val,
> > 
> >  	ad7949_adc->current_channel = channel;
> > 
> > -	*val = ad7949_adc->buffer & mask;
> > +	switch (ad7949_adc->bits_per_word) {
> > +	case 16:
> > +		*val = ad7949_adc->buffer;
> > +		/* Shift-out padding bits */
> > +		if (ad7949_adc->resolution == 14)
> > +			*val = *val >> 2;
> > +		break;
> > +	case 14:
> > +		*val = ad7949_adc->buffer & GENMASK(13, 0);
> > +		break;
> > +	case 8:
> > +		/* Convert byte array to u16, MSB first */
> > +		*val = (ad7949_adc->buf8[0] << 8) | ad7949_adc-
> > >buf8[1];
> > +		/* Shift-out padding bits */
> > +		if (ad7949_adc->resolution == 14)
> > +			*val = *val >> 2;
> > +		break;
> > +	}
> > 
> >  	return 0;
> >  }
> > @@ -280,6 +328,7 @@ static int ad7949_spi_probe(struct spi_device
> > *spi)
> >  	spec = &ad7949_adc_spec[spi_get_device_id(spi)-
> > >driver_data];
> >  	indio_dev->num_channels = spec->num_channels;
> >  	ad7949_adc->resolution = spec->resolution;
> > +	ad7949_set_bits_per_word(ad7949_adc);
> > 
> >  	ad7949_adc->vref = devm_regulator_get(dev, "vref");
> >  	if (IS_ERR(ad7949_adc->vref)) {
> > --
> > 2.30.1.489.g328c10930387

RE: [PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add adi,reference-source

[Liam Beguin]

On Fri Jul 9, 2021 at 4:15 AM EDT, Sa, Nuno wrote:
>
>
> > -----Original Message-----
> > From: Liam Beguin <liambeguin@gmail.com>
> > Sent: Friday, July 9, 2021 1:56 AM
> > To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> > <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> > antoine.couret@essensium.com
> > Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> > devicetree@vger.kernel.org; robh+dt@kernel.org
> > Subject: [PATCH v1 4/4] dt-bindings: iio: adc: ad7949: add
> > adi,reference-source
> > 
> > [External]
> > 
> > From: Liam Beguin <lvb@xiphos.com>
> > 
> > Add bindings documentation for the adi,reference-source property.
> > This property is required to properly configure the ADC sample request
> > based on which reference source should be used for the calculation.
> > 
> > Signed-off-by: Liam Beguin <lvb@xiphos.com>
> > ---
> >  .../bindings/iio/adc/adi,ad7949.yaml          | 22 +++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > index 9b56bd4d5510..3f4629281cc8 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
> > @@ -35,6 +35,28 @@ properties:
> >    "#io-channel-cells":
> >      const: 1
> > 
> > +  adi,reference-select:
> > +    allOf:
> > +      - $ref: /schemas/types.yaml#/definitions/uint32
> > +      - enum: [0, 1, 2, 3, 6, 7]
> > +
> > +    default: 7
> > +    description: |
> > +      Select the reference voltage source to use when converting
> > samples.
> > +      Acceptable values are:
> > +      - 0: Internal reference and temperature sensor enabled.
> > +           Vref=2.5V, buffered output
> > +      - 1: Internal reference and temperature sensor enabled.
> > +           Vref=4.096V, buffered output
> > +      - 2: Use external reference, temperature sensor enabled.
> > +           Internal buffer disabled
> > +      - 3: Use external reference, internal buffer and temperature
> > sensor
> > +           enabled.
> > +      - 6: Use external reference, internal buffer and temperature
> > sensor
> > +           disabled.
> > +      - 7: Use external reference, internal buffer enabled.
> > +           Internal reference and temperature sensor disabled.
>
> I think typically the description comes first. I also don't think you
> need the 'allOf'(not even sure if it will pass the binding check)...
> Just have '$ref' and 'enum' on the same level.
>

I realize I misread your comment on the order of the description. I'll
move it at the top of the binding definition.

Liam

> - Nuno Sá
>
> >  required:
> >    - compatible
> >    - reg
> > --
> > 2.30.1.489.g328c10930387

RE: [PATCH v1 3/4] iio: adc: ad7949: add support for internal vref

[Liam Beguin]

On Fri Jul 9, 2021 at 4:23 AM EDT, Sa, Nuno wrote:
> > From: Liam Beguin <liambeguin@gmail.com>
> > Sent: Friday, July 9, 2021 1:56 AM
> > To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> > <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> > antoine.couret@essensium.com
> > Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> > devicetree@vger.kernel.org; robh+dt@kernel.org
> > Subject: [PATCH v1 3/4] iio: adc: ad7949: add support for internal vref
> > 
> > [External]
> > 
> > From: Liam Beguin <lvb@xiphos.com>
> > 
> > Add support for selecting a custom reference voltage from the
> > devicetree. If an external source is used, a vref regulator should be
> > defined in the devicetree.
> > 
> > Signed-off-by: Liam Beguin <lvb@xiphos.com>
> > ---
> >  drivers/iio/adc/ad7949.c | 84
> > +++++++++++++++++++++++++++++++++-------
> >  1 file changed, 69 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > index bbc6b56330a3..3c1293922d2e 100644
> > --- a/drivers/iio/adc/ad7949.c
> > +++ b/drivers/iio/adc/ad7949.c
> > @@ -31,6 +31,7 @@
> >  #define AD7949_CFG_VAL_BW_FULL			1
> >  #define AD7949_CFG_VAL_BW_QUARTER		0
> >  #define AD7949_CFG_BIT_REF		GENMASK(5, 3)
> > +#define AD7949_CFG_VAL_REF_EXTERNAL		BIT(1)
> >  #define AD7949_CFG_BIT_SEQ		GENMASK(2, 1)
> >  #define AD7949_CFG_BIT_RBN		BIT(0)
> > 
> > @@ -40,6 +41,33 @@ enum {
> >  	ID_AD7689,
> >  };
> > 
> > +/**
> > + * enum ad7949_ref - Reference selection
> > + *
> > + * AD7949_REF_INT_2500:     Internal reference and temperature
> > sensor enabled.
> > + *                          Vref=2.5V, buffered output
> > + * AD7949_REF_INT_4096:     Internal reference and temperature
> > sensor enabled.
> > + *                          Vref=4.096V, buffered output
> > + * AD7949_REF_EXT_TEMP:     Use external reference, temperature
> > sensor enabled.
> > + *                          Internal buffer disabled
> > + * AD7949_REF_EXT_TEMP_BUF: Use external reference, internal
> > buffer and
> > + *                          temperature sensor enabled.
> > + * AD7949_REF_RSRV_4:       Do not use
> > + * AD7949_REF_RSRV_5:       Do not use
> > + * AD7949_REF_EXT:          Use external reference, internal buffer and
> > + *                          temperature sensor disabled.
> > + * AD7949_REF_EXT_BUF:      Use external reference, internal buffer
> > enabled.
> > + *                          Internal reference and temperature sensor disabled.
> > + */
> > +enum ad7949_ref {
> > +	AD7949_REF_INT_2500 = 0,
> > +	AD7949_REF_INT_4096,
> > +	AD7949_REF_EXT_TEMP,
> > +	AD7949_REF_EXT_TEMP_BUF,
> > +	AD7949_REF_EXT = 6,
> > +	AD7949_REF_EXT_BUF,
> > +};
> > +
> >  struct ad7949_adc_spec {
> >  	u8 num_channels;
> >  	u8 resolution;
> > @@ -55,6 +83,7 @@ static const struct ad7949_adc_spec
> > ad7949_adc_spec[] = {
> >   * struct ad7949_adc_chip - AD ADC chip
> >   * @lock: protects write sequences
> >   * @vref: regulator generating Vref
> > + * @refsel: reference selection
> >   * @indio_dev: reference to iio structure
> >   * @spi: reference to spi structure
> >   * @resolution: resolution of the chip
> > @@ -66,6 +95,7 @@ static const struct ad7949_adc_spec
> > ad7949_adc_spec[] = {
> >  struct ad7949_adc_chip {
> >  	struct mutex lock;
> >  	struct regulator *vref;
> > +	enum ad7949_ref refsel;
> >  	struct iio_dev *indio_dev;
> >  	struct spi_device *spi;
> >  	u8 resolution;
> > @@ -241,12 +271,28 @@ static int ad7949_spi_read_raw(struct iio_dev
> > *indio_dev,
> >  		return IIO_VAL_INT;
> > 
> >  	case IIO_CHAN_INFO_SCALE:
> > -		ret = regulator_get_voltage(ad7949_adc->vref);
> > -		if (ret < 0)
> > -			return ret;
> > +		switch (ad7949_adc->refsel) {
> > +		case AD7949_REF_INT_2500:
> > +			*val = 2500;
> > +			break;
> > +		case AD7949_REF_INT_4096:
> > +			*val = 4096;
> > +			break;
> > +		case AD7949_REF_EXT_TEMP:
> > +		case AD7949_REF_EXT_TEMP_BUF:
> > +		case AD7949_REF_EXT:
> > +		case AD7949_REF_EXT_BUF:
> > +			ret = regulator_get_voltage(ad7949_adc-
> > >vref);
> > +			if (ret < 0)
> > +				return ret;
> > +
> > +			/* convert value back to mV */
> > +			*val = ret / 1000;
> > +			break;
> > +		}
> > 
> > -		*val = ret / 5000;
> > -		return IIO_VAL_INT;
> > +		*val2 = (1 << ad7949_adc->resolution) - 1;
> > +		return IIO_VAL_FRACTIONAL;
> >  	}
> > 
> >  	return -EINVAL;
> > @@ -285,7 +331,7 @@ static int ad7949_spi_init(struct
> > ad7949_adc_chip *ad7949_adc)
> >  		FIELD_PREP(AD7949_CFG_BIT_INCC,
> > AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
> >  		FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc-
> > >current_channel) |
> >  		FIELD_PREP(AD7949_CFG_BIT_BW,
> > AD7949_CFG_VAL_BW_FULL) |
> > -		FIELD_PREP(AD7949_CFG_BIT_REF,
> > AD7949_REF_EXT_BUF) |
> > +		FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc-
> > >refsel) |
> >  		FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
> >  		FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
> > 
> > @@ -304,6 +350,7 @@ static int ad7949_spi_init(struct
> > ad7949_adc_chip *ad7949_adc)
> >  static int ad7949_spi_probe(struct spi_device *spi)
> >  {
> >  	struct device *dev = &spi->dev;
> > +	struct device_node *np = dev->of_node;
> >  	const struct ad7949_adc_spec *spec;
> >  	struct ad7949_adc_chip *ad7949_adc;
> >  	struct iio_dev *indio_dev;
> > @@ -315,6 +362,7 @@ static int ad7949_spi_probe(struct spi_device
> > *spi)
> >  		return -ENOMEM;
> >  	}
> > 
> > +	indio_dev->dev.of_node = np;
>
> Why doing this? The IIO core will do it for us at register time.

Sorry about that, will drop.

>
> >  	indio_dev->info = &ad7949_spi_info;
> >  	indio_dev->name = spi_get_device_id(spi)->name;
> >  	indio_dev->modes = INDIO_DIRECT_MODE;
> > @@ -330,16 +378,22 @@ static int ad7949_spi_probe(struct spi_device
> > *spi)
> >  	ad7949_adc->resolution = spec->resolution;
> >  	ad7949_set_bits_per_word(ad7949_adc);
> > 
> > -	ad7949_adc->vref = devm_regulator_get(dev, "vref");
> > -	if (IS_ERR(ad7949_adc->vref)) {
> > -		dev_err(dev, "fail to request regulator\n");
> > -		return PTR_ERR(ad7949_adc->vref);
> > -	}
> > +	/* Set default devicetree parameters */
> > +	ad7949_adc->refsel = AD7949_REF_EXT_BUF;
> > +	of_property_read_u32(np, "adi,reference-select",
> > &ad7949_adc->refsel);
>
> In case the property is given, we should make sure we get a valid
> value and error out if not...
>

I thought it would be handled later on when processing the sample, but
it's not really and it's better to fail early. I'll add that to v2.

Thanks,
Liam

> - Nuno Sá
> > -	ret = regulator_enable(ad7949_adc->vref);
> > -	if (ret < 0) {
> > -		dev_err(dev, "fail to enable regulator\n");
> > -		return ret;
> > +	if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
> > +		ad7949_adc->vref = devm_regulator_get(dev, "vref");
> > +		if (IS_ERR(ad7949_adc->vref)) {
> > +			dev_err(dev, "fail to request regulator\n");
> > +			return PTR_ERR(ad7949_adc->vref);
> > +		}
> > +
> > +		ret = regulator_enable(ad7949_adc->vref);
> > +		if (ret < 0) {
> > +			dev_err(dev, "fail to enable regulator\n");
> > +			return ret;
> > +		}
> >  	}
> > 
> >  	mutex_init(&ad7949_adc->lock);
> > --
> > 2.30.1.489.g328c10930387