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.
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
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 <[email protected]>
Signed-off-by: Dumitru Ceclan <[email protected]>
---
.../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
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 <[email protected]>
---
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