[PATCH 2/3] drivers: iio: adc: LTC2499 support

[Ciprian Regus]

The LTC2499 is a 16-channel (eight differential), 24-bit,
ADC with Easy Drive technology and a 2-wire, I2C interface.

Implement support for the LTC2499 ADC by extending the LTC2497
driver. A new chip_info struct is added to differentiate between
chip types and resolutions when reading data from the device.

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf

Signed-off-by: Ciprian Regus <ciprian.regus@xxxxxxxxxx>
---
 drivers/iio/adc/ltc2496.c      |  8 +++++++-
 drivers/iio/adc/ltc2497-core.c |  2 +-
 drivers/iio/adc/ltc2497.c      | 34 +++++++++++++++++++++++++++++-----
 drivers/iio/adc/ltc2497.h      | 13 ++++++++++++-
 4 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c
index dfb3bb5997e5..98338104c24a 100644
--- a/drivers/iio/adc/ltc2496.c
+++ b/drivers/iio/adc/ltc2496.c
@@ -14,6 +14,7 @@
 #include <linux/iio/iio.h>
 #include <linux/iio/driver.h>
 #include <linux/module.h>
+#include <linux/property.h>
 #include <linux/mod_devicetable.h>
 
 #include "ltc2497.h"
@@ -74,6 +75,7 @@ static int ltc2496_probe(struct spi_device *spi)
 	spi_set_drvdata(spi, indio_dev);
 	st->spi = spi;
 	st->common_ddata.result_and_measure = ltc2496_result_and_measure;
+	st->common_ddata.chip_info = device_get_match_data(dev);
 
 	return ltc2497core_probe(dev, indio_dev);
 }
@@ -85,8 +87,12 @@ static void ltc2496_remove(struct spi_device *spi)
 	ltc2497core_remove(indio_dev);
 }
 
+static struct chip_info ltc2496_info = {
+	.resolution = 16,
+};
+
 static const struct of_device_id ltc2496_of_match[] = {
-	{ .compatible = "lltc,ltc2496", },
+	{ .compatible = "lltc,ltc2496", .data = (void *)&ltc2496_info },
 	{},
 };
 MODULE_DEVICE_TABLE(of, ltc2496_of_match);
diff --git a/drivers/iio/adc/ltc2497-core.c b/drivers/iio/adc/ltc2497-core.c
index 2a485c8a1940..b2752399402c 100644
--- a/drivers/iio/adc/ltc2497-core.c
+++ b/drivers/iio/adc/ltc2497-core.c
@@ -95,7 +95,7 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev,
 			return ret;
 
 		*val = ret / 1000;
-		*val2 = 17;
+		*val2 = ddata->chip_info->resolution + 1;
 
 		return IIO_VAL_FRACTIONAL_LOG2;
 
diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
index f7c786f37ceb..bb5e0d4301e2 100644
--- a/drivers/iio/adc/ltc2497.c
+++ b/drivers/iio/adc/ltc2497.c
@@ -7,10 +7,14 @@
  * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
  */
 
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+
 #include <linux/i2c.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/driver.h>
 #include <linux/module.h>
+#include <linux/property.h>
 #include <linux/mod_devicetable.h>
 
 #include "ltc2497.h"
@@ -19,6 +23,8 @@ struct ltc2497_driverdata {
 	/* this must be the first member */
 	struct ltc2497core_driverdata common_ddata;
 	struct i2c_client *client;
+	u32 recv_size;
+	u32 sub_lsb;
 	/*
 	 * DMA (thus cache coherency maintenance) may require the
 	 * transfer buffers to live in their own cache lines.
@@ -34,13 +40,14 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
 	int ret;
 
 	if (val) {
-		ret = i2c_master_recv(st->client, (char *)&st->buf, 3);
+		ret = i2c_master_recv(st->client, (char *)&st->buf, st->recv_size);
 		if (ret < 0) {
 			dev_err(&st->client->dev, "i2c_master_recv failed\n");
 			return ret;
 		}
 
-		*val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
+		*val = (be32_to_cpu(st->buf) >> st->sub_lsb) -
+			BIT(ddata->chip_info->resolution + 1);
 	}
 
 	ret = i2c_smbus_write_byte(st->client,
@@ -54,6 +61,7 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
 static int ltc2497_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
+	u32 resolution;
 	struct iio_dev *indio_dev;
 	struct ltc2497_driverdata *st;
 	struct device *dev = &client->dev;
@@ -70,6 +78,11 @@ static int ltc2497_probe(struct i2c_client *client,
 	i2c_set_clientdata(client, indio_dev);
 	st->client = client;
 	st->common_ddata.result_and_measure = ltc2497_result_and_measure;
+	st->common_ddata.chip_info = device_get_match_data(dev);
+
+	resolution = st->common_ddata.chip_info->resolution;
+	st->sub_lsb = 31 - (resolution + 1);
+	st->recv_size = resolution / BITS_PER_BYTE + 1;
 
 	return ltc2497core_probe(dev, indio_dev);
 }
@@ -83,15 +96,26 @@ static int ltc2497_remove(struct i2c_client *client)
 	return 0;
 }
 
+static struct chip_info ltc2497_info[] = {
+	[TYPE_LTC2497] = {
+		.resolution = 16,
+	},
+	[TYPE_LTC2499] = {
+		.resolution = 24,
+	}
+};
+
 static const struct i2c_device_id ltc2497_id[] = {
-	{ "ltc2497", 0 },
+	{ "ltc2497", TYPE_LTC2497 },
+	{ "ltc2499", TYPE_LTC2499 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
 
 static const struct of_device_id ltc2497_of_match[] = {
-	{ .compatible = "lltc,ltc2497", },
-	{},
+	{ .compatible = "lltc,ltc2497", .data = (void *)&ltc2497_info[TYPE_LTC2497] },
+	{ .compatible = "lltc,ltc2499", .data = (void *)&ltc2497_info[TYPE_LTC2499] },
+	{}
 };
 MODULE_DEVICE_TABLE(of, ltc2497_of_match);
 
diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h
index d0b42dd6b8ad..f4d939cfd48b 100644
--- a/drivers/iio/adc/ltc2497.h
+++ b/drivers/iio/adc/ltc2497.h
@@ -4,9 +4,20 @@
 #define LTC2497_CONFIG_DEFAULT		LTC2497_ENABLE
 #define LTC2497_CONVERSION_TIME_MS	150ULL
 
+enum chip_type {
+	TYPE_LTC2496,
+	TYPE_LTC2497,
+	TYPE_LTC2499
+};
+
+struct chip_info {
+	u32 resolution;
+};
+
 struct ltc2497core_driverdata {
 	struct regulator *ref;
-	ktime_t	time_prev;
+	ktime_t time_prev;
+	const struct chip_info *chip_info;
 	u8 addr_prev;
 	int (*result_and_measure)(struct ltc2497core_driverdata *ddata,
 				  u8 address, int *val);
-- 
2.30.2