[PATCH v4 0/5] Add support for LTC6373

[PATCH v4 0/5] Add support for LTC6373

[Dumitru Ceclan]

This patch series adds support for the LTC6373 Instrumentation Amplifier within
the existing HMC425A driver.

The LTC6373 is a silicon, 3-bit Fully-Differential digital instrumentation
amplifier that supports the following programmable gains (Vout/Vin):
 G = 0.25, 0.5, 1, 2, 4, 8, 16 + Shutdown.
The programmable interface consists of 3 digitally controled inputs.

V3->V4
 - Fix git commit message typo and remove newline between tags
V2->V3
 - Use return instead of break in *_gain_dB_to_code()
 - Add new line before return in *_code_to_gain_dB()
 - Match parameter alignment for added _powerdown functions
 - Add precursor patch for using pointers in the match table
 - Add chip_info attributes: has_powerdown and powerdown_val
 - Change probe logic to use has_powerdown for default powerdown state
 - Added 'Fixes' tag to commit message of 'add conditional GPIO array...' 
V1->V2
 Driver:
 - Fix chip info table indent
 - Remove enable attribute
 - Add ext_info powerdown attribute
 - Enable by default powerdown attribute
 - Set default gain after disabling powerdown to min value
 Binding:
 - Fix conditional checking of GPIO array size for LTC6373
 - Add precursor commit for correctly checking gpio size depending upon compatible

Dumitru Ceclan (5):
  dt-bindings: iio: hmc425a: add conditional GPIO array size constraints
  dt-bindings: iio: hmc425a: add entry for LTC6373
  iio: amplifiers: hmc425a: move conversion logic
  iio: amplifiers: hmc425a: use pointers in match table
  iio: amplifiers: hmc425a: add support for LTC6373 Instrumentation
    Amplifier

 .../bindings/iio/amplifiers/adi,hmc425a.yaml  |  47 +++-
 drivers/iio/amplifiers/hmc425a.c              | 253 +++++++++++++-----
 2 files changed, 236 insertions(+), 64 deletions(-)

-- 
2.42.0

[PATCH v4 1/5] dt-bindings: iio: hmc425a: add conditional GPIO array size constraints

[Dumitru Ceclan]

ADRF5740 and HMC540S have a 4 bit parallel interface.
Update ctrl-gpios description and min/maxItems values depending on the
matched compatible to correctly reflect the hardware properties.

Fixes: 79f2ff6461e7 ("dt-bindings: iio: hmc425a: add entry for ADRF5740 Attenuator")
Fixes: 20f87a9a26be ("dt-bindings: iio: hmc425a: add entry for HMC540S")
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
---
 .../bindings/iio/amplifiers/adi,hmc425a.yaml  | 33 +++++++++++++++++--
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml b/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml
index 67de9d4e3a1d..a434cb8ddcc9 100644
--- a/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml
+++ b/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml
@@ -33,11 +33,38 @@ properties:
 
   ctrl-gpios:
     description:
-      Must contain an array of 6 GPIO specifiers, referring to the GPIO pins
-      connected to the control pins V1-V6.
-    minItems: 6
+      Must contain an array of GPIO specifiers, referring to the GPIO pins
+      connected to the control pins.
+        ADRF5740  - 4 GPIO connected to D2-D5
+        HMC540S   - 4 GPIO connected to V1-V4
+        HMC425A   - 6 GPIO connected to V1-V6
+    minItems: 1
     maxItems: 6
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,hmc425a
+    then:
+      properties:
+        ctrl-gpios:
+          minItems: 6
+          maxItems: 6
+  - if:
+      properties:
+        compatible:
+          contains:
+            anyOf:
+              - const: adi,adrf5740
+              - const: adi,hmc540s
+    then:
+      properties:
+        ctrl-gpios:
+          minItems: 4
+          maxItems: 4
+
 required:
   - compatible
   - ctrl-gpios
-- 
2.42.0

[PATCH v4 2/5] dt-bindings: iio: hmc425a: add entry for LTC6373

[Dumitru Ceclan]

The LTC6373 is a silicon, 3-bit Fully-Differential digital instrumentation
amplifier that supports the following programmable gains (Vout/Vin):
 G = 0.25, 0.5, 1, 2, 4, 8, 16 + Shutdown.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
---
 .../bindings/iio/amplifiers/adi,hmc425a.yaml       | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml b/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml
index a434cb8ddcc9..3a470459b965 100644
--- a/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml
+++ b/Documentation/devicetree/bindings/iio/amplifiers/adi,hmc425a.yaml
@@ -21,6 +21,8 @@ description: |
   HMC540S 1 dB LSB Silicon MMIC 4-Bit Digital Positive Control Attenuator, 0.1 - 8 GHz
     https://www.analog.com/media/en/technical-documentation/data-sheets/hmc540s.pdf
 
+  LTC6373 is a 3-Bit precision instrumentation amplifier with fully differential outputs
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ltc6373.pdf
 
 properties:
   compatible:
@@ -28,6 +30,7 @@ properties:
       - adi,adrf5740
       - adi,hmc425a
       - adi,hmc540s
+      - adi,ltc6373
 
   vcc-supply: true
 
@@ -38,6 +41,7 @@ properties:
         ADRF5740  - 4 GPIO connected to D2-D5
         HMC540S   - 4 GPIO connected to V1-V4
         HMC425A   - 6 GPIO connected to V1-V6
+        LTC6373   - 3 GPIO connected to A0-A2
     minItems: 1
     maxItems: 6
 
@@ -64,6 +68,16 @@ allOf:
         ctrl-gpios:
           minItems: 4
           maxItems: 4
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,ltc6373
+    then:
+      properties:
+        ctrl-gpios:
+          minItems: 3
+          maxItems: 3
 
 required:
   - compatible
-- 
2.42.0

[PATCH v4 3/5] iio: amplifiers: hmc425a: move conversion logic

[Dumitru Ceclan]

Move gain-dB<->code conversion logic from read_raw and write_raw to
hmc425a_gain_dB_to_code() and hmc425a_code_to_gain_dB().

Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
---
 drivers/iio/amplifiers/hmc425a.c | 102 ++++++++++++++++++-------------
 1 file changed, 59 insertions(+), 43 deletions(-)

diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
index ed4d72922696..e1162a500daf 100644
--- a/drivers/iio/amplifiers/hmc425a.c
+++ b/drivers/iio/amplifiers/hmc425a.c
@@ -56,35 +56,72 @@ static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
 	return 0;
 }
 
+static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
+{
+	struct hmc425a_chip_info *inf = st->chip_info;
+	int gain, temp;
+
+	if (val < 0)
+		gain = (val * 1000) - (val2 / 1000);
+	else
+		gain = (val * 1000) + (val2 / 1000);
+
+	if (gain > inf->gain_max || gain < inf->gain_min)
+		return -EINVAL;
+
+	switch (st->type) {
+	case ID_HMC425A:
+		*code = ~((abs(gain) / 500) & 0x3F);
+		return 0;
+	case ID_HMC540S:
+		*code = ~((abs(gain) / 1000) & 0xF);
+		return 0;
+	case ID_ADRF5740:
+		temp = (abs(gain) / 2000) & 0xF;
+		*code = temp & BIT(3) ? temp | BIT(2) : temp;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int hmc425a_code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2)
+{
+	int code, gain;
+
+	code = st->gain;
+	switch (st->type) {
+	case ID_HMC425A:
+		gain = ~code * -500;
+		break;
+	case ID_HMC540S:
+		gain = ~code * -1000;
+		break;
+	case ID_ADRF5740:
+		code = code & BIT(3) ? code & ~BIT(2) : code;
+		gain = code * -2000;
+		break;
+	}
+
+	*val = gain / 1000;
+	*val2 = (gain % 1000) * 1000;
+
+	return 0;
+}
+
 static int hmc425a_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan, int *val,
 			    int *val2, long m)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);
-	int code, gain = 0;
 	int ret;
 
 	mutex_lock(&st->lock);
 	switch (m) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
-		code = st->gain;
-
-		switch (st->type) {
-		case ID_HMC425A:
-			gain = ~code * -500;
-			break;
-		case ID_HMC540S:
-			gain = ~code * -1000;
+		ret = hmc425a_code_to_gain_dB(st, val, val2);
+		if (ret)
 			break;
-		case ID_ADRF5740:
-			code = code & BIT(3) ? code & ~BIT(2) : code;
-			gain = code * -2000;
-			break;
-		}
-
-		*val = gain / 1000;
-		*val2 = (gain % 1000) * 1000;
-
 		ret = IIO_VAL_INT_PLUS_MICRO_DB;
 		break;
 	default:
@@ -100,36 +137,15 @@ static int hmc425a_write_raw(struct iio_dev *indio_dev,
 			     int val2, long mask)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);
-	struct hmc425a_chip_info *inf = st->chip_info;
-	int code = 0, gain;
-	int ret;
-
-	if (val < 0)
-		gain = (val * 1000) - (val2 / 1000);
-	else
-		gain = (val * 1000) + (val2 / 1000);
-
-	if (gain > inf->gain_max || gain < inf->gain_min)
-		return -EINVAL;
-
-	switch (st->type) {
-	case ID_HMC425A:
-		code = ~((abs(gain) / 500) & 0x3F);
-		break;
-	case ID_HMC540S:
-		code = ~((abs(gain) / 1000) & 0xF);
-		break;
-	case ID_ADRF5740:
-		code = (abs(gain) / 2000) & 0xF;
-		code = code & BIT(3) ? code | BIT(2) : code;
-		break;
-	}
+	int code = 0, ret;
 
 	mutex_lock(&st->lock);
 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
+		ret = hmc425a_gain_dB_to_code(st, val, val2, &code);
+		if (ret)
+			break;
 		st->gain = code;
-
 		ret = hmc425a_write(indio_dev, st->gain);
 		break;
 	default:
-- 
2.42.0

[PATCH v4 4/5] iio: amplifiers: hmc425a: use pointers in match table

[Dumitru Ceclan]

Change the match table to use pointers instead of device ids.
Alignment of the hmc425a_state was changed because of the const
 specifier for hmc425a_chip_info.

Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
---
 drivers/iio/amplifiers/hmc425a.c | 39 ++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
index e1162a500daf..b116b54e4206 100644
--- a/drivers/iio/amplifiers/hmc425a.c
+++ b/drivers/iio/amplifiers/hmc425a.c
@@ -37,11 +37,11 @@ struct hmc425a_chip_info {
 };
 
 struct hmc425a_state {
-	struct	mutex lock; /* protect sensor state */
-	struct	hmc425a_chip_info *chip_info;
-	struct	gpio_descs *gpios;
-	enum	hmc425a_type type;
-	u32	gain;
+	struct				mutex lock; /* protect sensor state */
+	const struct			hmc425a_chip_info *chip_info;
+	struct				gpio_descs *gpios;
+	enum				hmc425a_type type;
+	u32				gain;
 };
 
 static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
@@ -58,7 +58,7 @@ static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
 
 static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
 {
-	struct hmc425a_chip_info *inf = st->chip_info;
+	const struct hmc425a_chip_info *inf = st->chip_info;
 	int gain, temp;
 
 	if (val < 0)
@@ -187,15 +187,6 @@ static const struct iio_chan_spec hmc425a_channels[] = {
 	HMC425A_CHAN(0),
 };
 
-/* Match table for of_platform binding */
-static const struct of_device_id hmc425a_of_match[] = {
-	{ .compatible = "adi,hmc425a", .data = (void *)ID_HMC425A },
-	{ .compatible = "adi,hmc540s", .data = (void *)ID_HMC540S },
-	{ .compatible = "adi,adrf5740", .data = (void *)ID_ADRF5740 },
-	{},
-};
-MODULE_DEVICE_TABLE(of, hmc425a_of_match);
-
 static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
 	[ID_HMC425A] = {
 		.name = "hmc425a",
@@ -226,6 +217,18 @@ static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
 	},
 };
 
+/* Match table for of_platform binding */
+static const struct of_device_id hmc425a_of_match[] = {
+	{ .compatible = "adi,hmc425a",
+	  .data = &hmc425a_chip_info_tbl[ID_HMC425A]},
+	{ .compatible = "adi,hmc540s",
+	  .data = &hmc425a_chip_info_tbl[ID_HMC540S]},
+	{ .compatible = "adi,adrf5740",
+	  .data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
+	{},
+};
+MODULE_DEVICE_TABLE(of, hmc425a_of_match);
+
 static int hmc425a_probe(struct platform_device *pdev)
 {
 	struct iio_dev *indio_dev;
@@ -237,14 +240,16 @@ static int hmc425a_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	st = iio_priv(indio_dev);
-	st->type = (uintptr_t)device_get_match_data(&pdev->dev);
 
-	st->chip_info = &hmc425a_chip_info_tbl[st->type];
+	st->chip_info = device_get_match_data(&pdev->dev);
 	indio_dev->num_channels = st->chip_info->num_channels;
 	indio_dev->channels = st->chip_info->channels;
 	indio_dev->name = st->chip_info->name;
 	st->gain = st->chip_info->default_gain;
 
+	/* Compute index of the acquired chip info in the array */
+	st->type = st->chip_info - hmc425a_chip_info_tbl;
+
 	st->gpios = devm_gpiod_get_array(&pdev->dev, "ctrl", GPIOD_OUT_LOW);
 	if (IS_ERR(st->gpios))
 		return dev_err_probe(&pdev->dev, PTR_ERR(st->gpios),
-- 
2.42.0

[PATCH v4 5/5] iio: amplifiers: hmc425a: add support for LTC6373 Instrumentation Amplifier

[Dumitru Ceclan]

This adds support for LTC6373 36 V Fully-Differential Programmable-Gain
Instrumentation Amplifier with 25 pA Input Bias Current.
The user can program the gain to one of seven available settings through
a 3-bit parallel interface (A2 to A0).

Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
---
 drivers/iio/amplifiers/hmc425a.c | 118 +++++++++++++++++++++++++++++--
 1 file changed, 114 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
index b116b54e4206..e7f425677fd3 100644
--- a/drivers/iio/amplifiers/hmc425a.c
+++ b/drivers/iio/amplifiers/hmc425a.c
@@ -2,9 +2,10 @@
 /*
  * HMC425A and similar Gain Amplifiers
  *
- * Copyright 2020 Analog Devices Inc.
+ * Copyright 2020, 2023 Analog Devices Inc.
  */
 
+#include <linux/bits.h>
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -20,10 +21,24 @@
 #include <linux/regulator/consumer.h>
 #include <linux/sysfs.h>
 
+/*
+ * The LTC6373 amplifier supports configuring gain using GPIO's with the following
+ *  values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
+ *
+ * Except for the shutdown value, all can be converted to dB using 20 * log10(x)
+ * From here, it is observed that all values are multiples of the '2' gain setting,
+ *  with the correspondent of 6.020dB.
+ */
+#define LTC6373_CONVERSION_CONSTANT	6020
+#define LTC6373_MIN_GAIN_CODE		0x6
+#define LTC6373_CONVERSION_MASK		GENMASK(2, 0)
+#define LTC6373_SHUTDOWN		GENMASK(2, 0)
+
 enum hmc425a_type {
 	ID_HMC425A,
 	ID_HMC540S,
-	ID_ADRF5740
+	ID_ADRF5740,
+	ID_LTC6373,
 };
 
 struct hmc425a_chip_info {
@@ -34,6 +49,8 @@ struct hmc425a_chip_info {
 	int				gain_min;
 	int				gain_max;
 	int				default_gain;
+	int				powerdown_val;
+	bool				has_powerdown;
 };
 
 struct hmc425a_state {
@@ -42,6 +59,7 @@ struct hmc425a_state {
 	struct				gpio_descs *gpios;
 	enum				hmc425a_type type;
 	u32				gain;
+	bool				powerdown;
 };
 
 static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
@@ -80,6 +98,17 @@ static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2,
 		temp = (abs(gain) / 2000) & 0xF;
 		*code = temp & BIT(3) ? temp | BIT(2) : temp;
 		return 0;
+	case ID_LTC6373:
+		if (st->powerdown)
+			return -EPERM;
+
+		/* add half of the value for rounding */
+		temp = LTC6373_CONVERSION_CONSTANT / 2;
+		if (val < 0)
+			temp *= -1;
+		*code = ~((gain + temp) / LTC6373_CONVERSION_CONSTANT + 3)
+			& LTC6373_CONVERSION_MASK;
+		return 0;
 	default:
 		return -EINVAL;
 	}
@@ -101,6 +130,12 @@ static int hmc425a_code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2
 		code = code & BIT(3) ? code & ~BIT(2) : code;
 		gain = code * -2000;
 		break;
+	case ID_LTC6373:
+		if (st->powerdown)
+			return -EPERM;
+		gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
+		       LTC6373_CONVERSION_CONSTANT;
+		break;
 	}
 
 	*val = gain / 1000;
@@ -174,6 +209,48 @@ static const struct iio_info hmc425a_info = {
 	.write_raw_get_fmt = &hmc425a_write_raw_get_fmt,
 };
 
+static ssize_t ltc6373_read_powerdown(struct iio_dev *indio_dev,
+				      uintptr_t private,
+				      const struct iio_chan_spec *chan,
+				      char *buf)
+{
+	struct hmc425a_state *st = iio_priv(indio_dev);
+
+	return sysfs_emit(buf, "%d\n", st->powerdown);
+}
+
+static ssize_t ltc6373_write_powerdown(struct iio_dev *indio_dev,
+				       uintptr_t private,
+				       const struct iio_chan_spec *chan,
+				       const char *buf,
+				       size_t len)
+{
+	struct hmc425a_state *st = iio_priv(indio_dev);
+	bool powerdown;
+	int code, ret;
+
+	ret = kstrtobool(buf, &powerdown);
+	if (ret)
+		return ret;
+
+	mutex_lock(&st->lock);
+	st->powerdown = powerdown;
+	code = (powerdown) ? LTC6373_SHUTDOWN : st->gain;
+	ret = hmc425a_write(indio_dev, code);
+	mutex_unlock(&st->lock);
+	return len;
+}
+
+static const struct iio_chan_spec_ext_info ltc6373_ext_info[] = {
+	{
+		.name = "powerdown",
+		.read = ltc6373_read_powerdown,
+		.write = ltc6373_write_powerdown,
+		.shared = IIO_SEPARATE,
+	},
+	{},
+};
+
 #define HMC425A_CHAN(_channel)						\
 {									\
 	.type = IIO_VOLTAGE,						\
@@ -183,10 +260,24 @@ static const struct iio_info hmc425a_info = {
 	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),		\
 }
 
+#define LTC6373_CHAN(_channel)						\
+{									\
+	.type = IIO_VOLTAGE,						\
+	.output = 1,							\
+	.indexed = 1,							\
+	.channel = _channel,						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),		\
+	.ext_info = ltc6373_ext_info,					\
+}
+
 static const struct iio_chan_spec hmc425a_channels[] = {
 	HMC425A_CHAN(0),
 };
 
+static const struct iio_chan_spec ltc6373_channels[] = {
+	LTC6373_CHAN(0),
+};
+
 static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
 	[ID_HMC425A] = {
 		.name = "hmc425a",
@@ -215,6 +306,18 @@ static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
 		.gain_max = 0,
 		.default_gain = 0xF, /* set default gain -22.0db*/
 	},
+	[ID_LTC6373] = {
+		.name = "ltc6373",
+		.channels = ltc6373_channels,
+		.num_channels = ARRAY_SIZE(ltc6373_channels),
+		.num_gpios = 3,
+		.gain_min = -12041, /* gain setting x0.25*/
+		.gain_max = 24082,  /* gain setting x16  */
+		.default_gain = LTC6373_MIN_GAIN_CODE,
+		.powerdown_val = LTC6373_SHUTDOWN,
+		.has_powerdown = true,
+	},
+
 };
 
 /* Match table for of_platform binding */
@@ -225,6 +328,8 @@ static const struct of_device_id hmc425a_of_match[] = {
 	  .data = &hmc425a_chip_info_tbl[ID_HMC540S]},
 	{ .compatible = "adi,adrf5740",
 	  .data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
+	{ .compatible = "adi,ltc6373",
+	  .data = &hmc425a_chip_info_tbl[ID_LTC6373]},
 	{},
 };
 MODULE_DEVICE_TABLE(of, hmc425a_of_match);
@@ -270,8 +375,13 @@ static int hmc425a_probe(struct platform_device *pdev)
 	indio_dev->info = &hmc425a_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
-	/* Set default gain */
-	hmc425a_write(indio_dev, st->gain);
+	if (st->chip_info->has_powerdown) {
+		st->powerdown = true;
+		hmc425a_write(indio_dev, st->chip_info->powerdown_val);
+	} else {
+		/* Set default gain */
+		hmc425a_write(indio_dev, st->gain);
+	}
 
 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }
-- 
2.42.0

Re: [PATCH v4 4/5] iio: amplifiers: hmc425a: use pointers in match table

[Jonathan Cameron]

On Wed, 17 Jan 2024 14:51:13 +0200
Dumitru Ceclan <mitrutzceclan@gmail.com> wrote:

> Change the match table to use pointers instead of device ids.
> Alignment of the hmc425a_state was changed because of the const
>  specifier for hmc425a_chip_info.
> 
> Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
Hi Dumitru

The remaining use of type in here and deriving from structure offsets is
not nice.  Add a trivial callback for the stuff in write_raw() that needs
to be different and is currently in a switch statement.
Then get rid of the type enum completely if possible.

> ---
>  drivers/iio/amplifiers/hmc425a.c | 39 ++++++++++++++++++--------------
>  1 file changed, 22 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
> index e1162a500daf..b116b54e4206 100644
> --- a/drivers/iio/amplifiers/hmc425a.c
> +++ b/drivers/iio/amplifiers/hmc425a.c
> @@ -37,11 +37,11 @@ struct hmc425a_chip_info {
>  };
>  
>  struct hmc425a_state {
> -	struct	mutex lock; /* protect sensor state */
> -	struct	hmc425a_chip_info *chip_info;
> -	struct	gpio_descs *gpios;
> -	enum	hmc425a_type type;
> -	u32	gain;
> +	struct				mutex lock; /* protect sensor state */
> +	const struct			hmc425a_chip_info *chip_info;
> +	struct				gpio_descs *gpios;
> +	enum				hmc425a_type type;
> +	u32				gain;

This illustrates why I'm not keen on manual alignment like this. Generates 
churn that makes it hard to spot the actual changes.  To avoid this happening
again I'd suggest a single space is fine for all lines and don't align them
at all!

>  };
>  
>  static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
> @@ -58,7 +58,7 @@ static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
>  
>  static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
>  {
> -	struct hmc425a_chip_info *inf = st->chip_info;
> +	const struct hmc425a_chip_info *inf = st->chip_info;
>  	int gain, temp;
>  
>  	if (val < 0)
> @@ -187,15 +187,6 @@ static const struct iio_chan_spec hmc425a_channels[] = {
>  	HMC425A_CHAN(0),
>  };
>  
> -/* Match table for of_platform binding */
> -static const struct of_device_id hmc425a_of_match[] = {
> -	{ .compatible = "adi,hmc425a", .data = (void *)ID_HMC425A },
> -	{ .compatible = "adi,hmc540s", .data = (void *)ID_HMC540S },
> -	{ .compatible = "adi,adrf5740", .data = (void *)ID_ADRF5740 },
> -	{},
> -};
> -MODULE_DEVICE_TABLE(of, hmc425a_of_match);
> -
>  static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
>  	[ID_HMC425A] = {
>  		.name = "hmc425a",
> @@ -226,6 +217,18 @@ static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
>  	},
>  };
>  
> +/* Match table for of_platform binding */
> +static const struct of_device_id hmc425a_of_match[] = {
> +	{ .compatible = "adi,hmc425a",
> +	  .data = &hmc425a_chip_info_tbl[ID_HMC425A]},
> +	{ .compatible = "adi,hmc540s",
> +	  .data = &hmc425a_chip_info_tbl[ID_HMC540S]},
> +	{ .compatible = "adi,adrf5740",
> +	  .data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
> +	{},

Nice to drop that trailing comma whilst here.  No need for one on a 'terminator'
of such an array as by definition nothing should ever be added after it.

> +};
> +MODULE_DEVICE_TABLE(of, hmc425a_of_match);
> +
>  static int hmc425a_probe(struct platform_device *pdev)
>  {
>  	struct iio_dev *indio_dev;
> @@ -237,14 +240,16 @@ static int hmc425a_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	st = iio_priv(indio_dev);
> -	st->type = (uintptr_t)device_get_match_data(&pdev->dev);
>  
> -	st->chip_info = &hmc425a_chip_info_tbl[st->type];
> +	st->chip_info = device_get_match_data(&pdev->dev);
>  	indio_dev->num_channels = st->chip_info->num_channels;
>  	indio_dev->channels = st->chip_info->channels;
>  	indio_dev->name = st->chip_info->name;
>  	st->gain = st->chip_info->default_gain;
>  
> +	/* Compute index of the acquired chip info in the array */
> +	st->type = st->chip_info - hmc425a_chip_info_tbl;

Definitely not a good idea. If you need a type field, put it in the chip_info_tbl
but you should not need one anyway because type is rarely what matters
but rather data or behavior (via a callback) needed for a given device.
Here it looks like a callback is needed for the few lines in write_raw()
that are fiddly to express as data.

> +
>  	st->gpios = devm_gpiod_get_array(&pdev->dev, "ctrl", GPIOD_OUT_LOW);
>  	if (IS_ERR(st->gpios))
>  		return dev_err_probe(&pdev->dev, PTR_ERR(st->gpios),

Re: [PATCH v4 3/5] iio: amplifiers: hmc425a: move conversion logic

[Jonathan Cameron]

On Wed, 17 Jan 2024 14:51:12 +0200
Dumitru Ceclan <mitrutzceclan@gmail.com> wrote:

> Move gain-dB<->code conversion logic from read_raw and write_raw to
> hmc425a_gain_dB_to_code() and hmc425a_code_to_gain_dB().
> 
> Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
Some comments inline

Jonathan

> ---
>  drivers/iio/amplifiers/hmc425a.c | 102 ++++++++++++++++++-------------
>  1 file changed, 59 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
> index ed4d72922696..e1162a500daf 100644
> --- a/drivers/iio/amplifiers/hmc425a.c
> +++ b/drivers/iio/amplifiers/hmc425a.c
> @@ -56,35 +56,72 @@ static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
>  	return 0;
>  }
>  
> +static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
> +{
> +	struct hmc425a_chip_info *inf = st->chip_info;
> +	int gain, temp;
> +
> +	if (val < 0)
> +		gain = (val * 1000) - (val2 / 1000);
> +	else
> +		gain = (val * 1000) + (val2 / 1000);
> +
> +	if (gain > inf->gain_max || gain < inf->gain_min)
> +		return -EINVAL;
> +
> +	switch (st->type) {
> +	case ID_HMC425A:
> +		*code = ~((abs(gain) / 500) & 0x3F);

In the next patch I point out that this should be data or callbacks in in
the st->chip_info structure, not encoded in code here based on st->type (which
I want you to get rid of!)

> +		return 0;
> +	case ID_HMC540S:
> +		*code = ~((abs(gain) / 1000) & 0xF);
> +		return 0;
> +	case ID_ADRF5740:
> +		temp = (abs(gain) / 2000) & 0xF;
> +		*code = temp & BIT(3) ? temp | BIT(2) : temp;

Given you are moving the code, a comment here might be nice as it's unusual
(bits are 2DB, 4DB, 8DB and another 8DB)

> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int hmc425a_code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2)
> +{
> +	int code, gain;
> +
> +	code = st->gain;
> +	switch (st->type) {
> +	case ID_HMC425A:
> +		gain = ~code * -500;
> +		break;
> +	case ID_HMC540S:
> +		gain = ~code * -1000;
> +		break;
> +	case ID_ADRF5740:
> +		code = code & BIT(3) ? code & ~BIT(2) : code;
> +		gain = code * -2000;
> +		break;
> +	}
> +
> +	*val = gain / 1000;
> +	*val2 = (gain % 1000) * 1000;
> +
> +	return 0;
> +}
> +
>  static int hmc425a_read_raw(struct iio_dev *indio_dev,
>  			    struct iio_chan_spec const *chan, int *val,
>  			    int *val2, long m)
>  {
>  	struct hmc425a_state *st = iio_priv(indio_dev);
> -	int code, gain = 0;
>  	int ret;
>  
>  	mutex_lock(&st->lock);
>  	switch (m) {
>  	case IIO_CHAN_INFO_HARDWAREGAIN:
> -		code = st->gain;
> -
> -		switch (st->type) {
> -		case ID_HMC425A:
> -			gain = ~code * -500;
> -			break;
> -		case ID_HMC540S:
> -			gain = ~code * -1000;
> +		ret = hmc425a_code_to_gain_dB(st, val, val2);
> +		if (ret)
>  			break;
> -		case ID_ADRF5740:
> -			code = code & BIT(3) ? code & ~BIT(2) : code;
> -			gain = code * -2000;
> -			break;
> -		}
> -
> -		*val = gain / 1000;
> -		*val2 = (gain % 1000) * 1000;
> -
>  		ret = IIO_VAL_INT_PLUS_MICRO_DB;
>  		break;
>  	default:
> @@ -100,36 +137,15 @@ static int hmc425a_write_raw(struct iio_dev *indio_dev,
>  			     int val2, long mask)
>  {
>  	struct hmc425a_state *st = iio_priv(indio_dev);
> -	struct hmc425a_chip_info *inf = st->chip_info;
> -	int code = 0, gain;
> -	int ret;
> -
> -	if (val < 0)
> -		gain = (val * 1000) - (val2 / 1000);
> -	else
> -		gain = (val * 1000) + (val2 / 1000);
> -
> -	if (gain > inf->gain_max || gain < inf->gain_min)
> -		return -EINVAL;
> -
> -	switch (st->type) {
> -	case ID_HMC425A:
> -		code = ~((abs(gain) / 500) & 0x3F);
> -		break;
> -	case ID_HMC540S:
> -		code = ~((abs(gain) / 1000) & 0xF);
> -		break;
> -	case ID_ADRF5740:
> -		code = (abs(gain) / 2000) & 0xF;
> -		code = code & BIT(3) ? code | BIT(2) : code;
> -		break;
> -	}
> +	int code = 0, ret;
>  
>  	mutex_lock(&st->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_HARDWAREGAIN:
> +		ret = hmc425a_gain_dB_to_code(st, val, val2, &code);
> +		if (ret)
> +			break;
>  		st->gain = code;
> -
>  		ret = hmc425a_write(indio_dev, st->gain);
>  		break;
>  	default:

Re: [PATCH v4 5/5] iio: amplifiers: hmc425a: add support for LTC6373 Instrumentation Amplifier

[Jonathan Cameron]

On Wed, 17 Jan 2024 14:51:14 +0200
Dumitru Ceclan <mitrutzceclan@gmail.com> wrote:

> This adds support for LTC6373 36 V Fully-Differential Programmable-Gain
> Instrumentation Amplifier with 25 pA Input Bias Current.
> The user can program the gain to one of seven available settings through
> a 3-bit parallel interface (A2 to A0).
> 
> Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
Hi Dumitru,

Some comments inline.  I'd forgotten we have a rich set of DIV_xxx macros
in math.h, DIV_ROUND_CLOSEST is I think the same as what you have
coded up in here.

> ---
>  drivers/iio/amplifiers/hmc425a.c | 118 +++++++++++++++++++++++++++++--
>  1 file changed, 114 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
> index b116b54e4206..e7f425677fd3 100644
> --- a/drivers/iio/amplifiers/hmc425a.c
> +++ b/drivers/iio/amplifiers/hmc425a.c
> @@ -2,9 +2,10 @@
>  /*
>   * HMC425A and similar Gain Amplifiers
>   *
> - * Copyright 2020 Analog Devices Inc.
> + * Copyright 2020, 2023 Analog Devices Inc.
>   */
>  
> +#include <linux/bits.h>
>  #include <linux/bitops.h>
>  #include <linux/device.h>
>  #include <linux/err.h>
> @@ -20,10 +21,24 @@
>  #include <linux/regulator/consumer.h>
>  #include <linux/sysfs.h>
>  
> +/*
> + * The LTC6373 amplifier supports configuring gain using GPIO's with the following
> + *  values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
> + *
> + * Except for the shutdown value, all can be converted to dB using 20 * log10(x)
> + * From here, it is observed that all values are multiples of the '2' gain setting,
> + *  with the correspondent of 6.020dB.
> + */
> +#define LTC6373_CONVERSION_CONSTANT	6020
> +#define LTC6373_MIN_GAIN_CODE		0x6
> +#define LTC6373_CONVERSION_MASK		GENMASK(2, 0)
> +#define LTC6373_SHUTDOWN		GENMASK(2, 0)
> +
>  enum hmc425a_type {
>  	ID_HMC425A,
>  	ID_HMC540S,
> -	ID_ADRF5740
> +	ID_ADRF5740,
> +	ID_LTC6373,
>  };
>  
>  struct hmc425a_chip_info {
> @@ -34,6 +49,8 @@ struct hmc425a_chip_info {
>  	int				gain_min;
>  	int				gain_max;
>  	int				default_gain;
> +	int				powerdown_val;
> +	bool				has_powerdown;
>  };
>  
>  struct hmc425a_state {
> @@ -42,6 +59,7 @@ struct hmc425a_state {
>  	struct				gpio_descs *gpios;
>  	enum				hmc425a_type type;
>  	u32				gain;
> +	bool				powerdown;
>  };
>  
>  static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
> @@ -80,6 +98,17 @@ static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2,
>  		temp = (abs(gain) / 2000) & 0xF;
>  		*code = temp & BIT(3) ? temp | BIT(2) : temp;
>  		return 0;
> +	case ID_LTC6373:
> +		if (st->powerdown)
> +			return -EPERM;
> +
> +		/* add half of the value for rounding */
> +		temp = LTC6373_CONVERSION_CONSTANT / 2;

As mentioned in review of earlier patch, I'd like this to be in a callback not
based on st->type (which should be removed from the driver).

> +		if (val < 0)
> +			temp *= -1;
> +		*code = ~((gain + temp) / LTC6373_CONVERSION_CONSTANT + 3)

I'd forgotten in previous reviews that we have DIV_ROUND_CLOSEST() that does
pretty similar maths to your handling here. Better to use that than
spin your own version.

> +			& LTC6373_CONVERSION_MASK;
> +		return 0;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -101,6 +130,12 @@ static int hmc425a_code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2
>  		code = code & BIT(3) ? code & ~BIT(2) : code;
>  		gain = code * -2000;
>  		break;
> +	case ID_LTC6373:
> +		if (st->powerdown)
> +			return -EPERM;
> +		gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
> +		       LTC6373_CONVERSION_CONSTANT;
> +		break;
>  	}
>  
>  	*val = gain / 1000;
> @@ -174,6 +209,48 @@ static const struct iio_info hmc425a_info = {
>  	.write_raw_get_fmt = &hmc425a_write_raw_get_fmt,
>  };
>  

> +
> +static const struct iio_chan_spec_ext_info ltc6373_ext_info[] = {
> +	{
> +		.name = "powerdown",
> +		.read = ltc6373_read_powerdown,
> +		.write = ltc6373_write_powerdown,
> +		.shared = IIO_SEPARATE,
> +	},
> +	{},

No comma preferred after a terminator entry like this as nothing should
ever come after it.  Any new additions must be before this last entry.


> +};

Re: [PATCH v4 5/5] iio: amplifiers: hmc425a: add support for LTC6373 Instrumentation Amplifier

[Petre Rodan]

[-- Attachment #1: Type: text/plain, Size: 318 bytes --]


hello Dumitru,

I know this is not part of your current patch, but you might also want to have
a look at ltc6373_write_powerdown():

hmc425a.c:239:2: warning: Value stored to 'ret' is never read [deadcode.DeadStores]
  239 |         ret = hmc425a_write(indio_dev, code);

cheers,
peter

-- 
petre rodan

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]