[PATCH] hwmon: (aht10) Add support for dht20

[Akhilesh Patil]

Add support for dht20 temperature and humidity sensor from Aosong.
Modify aht10 driver to handle different init command for dht20 sensor by
adding init_cmd entry in the driver data. dht20 sensor is compatible with
aht10 hwmon driver with this change.

Tested on TI am62x SK board with dht20 sensor connected at i2c-2 port.

Signed-off-by: Akhilesh Patil <akhilesh@xxxxxxxxxxxxx>
---
 Documentation/hwmon/aht10.rst | 10 +++++++++-
 drivers/hwmon/Kconfig         |  6 +++---
 drivers/hwmon/aht10.c         | 19 ++++++++++++++++---
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/Documentation/hwmon/aht10.rst b/Documentation/hwmon/aht10.rst
index 213644b4ecba..7903b6434326 100644
--- a/Documentation/hwmon/aht10.rst
+++ b/Documentation/hwmon/aht10.rst
@@ -20,6 +20,14 @@ Supported chips:
 
       English: http://www.aosong.com/userfiles/files/media/Data%20Sheet%20AHT20.pdf
 
+  * Aosong DHT20
+
+    Prefix: 'dht20'
+
+    Addresses scanned: None
+
+    Datasheet: https://www.digikey.co.nz/en/htmldatasheets/production/9184855/0/0/1/101020932
+
 Author: Johannes Cornelis Draaijer <jcdra1@xxxxxxxxx>
 
 
@@ -33,7 +41,7 @@ The address of this i2c device may only be 0x38
 Special Features
 ----------------
 
-AHT20 has additional CRC8 support which is sent as the last byte of the sensor
+AHT20, DHT20 has additional CRC8 support which is sent as the last byte of the sensor
 values.
 
 Usage Notes
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 2760feb9f83b..2a71b6e834b0 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -245,12 +245,12 @@ config SENSORS_ADT7475
 	  will be called adt7475.
 
 config SENSORS_AHT10
-	tristate "Aosong AHT10, AHT20"
+	tristate "Aosong AHT10, AHT20, DHT20"
 	depends on I2C
 	select CRC8
 	help
-	  If you say yes here, you get support for the Aosong AHT10 and AHT20
-	  temperature and humidity sensors
+	  If you say yes here, you get support for the Aosong AHT10, AHT20 and
+	  DHT20 temperature and humidity sensors
 
 	  This driver can also be built as a module. If so, the module
 	  will be called aht10.
diff --git a/drivers/hwmon/aht10.c b/drivers/hwmon/aht10.c
index d1c55e2eb479..a153282eef6a 100644
--- a/drivers/hwmon/aht10.c
+++ b/drivers/hwmon/aht10.c
@@ -37,6 +37,8 @@
 #define AHT10_CMD_MEAS	0b10101100
 #define AHT10_CMD_RST	0b10111010
 
+#define DHT20_CMD_INIT	0x71
+
 /*
  * Flags in the answer byte/command
  */
@@ -48,11 +50,12 @@
 
 #define AHT10_MAX_POLL_INTERVAL_LEN	30
 
-enum aht10_variant { aht10, aht20 };
+enum aht10_variant { aht10, aht20, dht20};
 
 static const struct i2c_device_id aht10_id[] = {
 	{ "aht10", aht10 },
 	{ "aht20", aht20 },
+	{ "dht20", dht20 },
 	{ },
 };
 MODULE_DEVICE_TABLE(i2c, aht10_id);
@@ -77,6 +80,7 @@ MODULE_DEVICE_TABLE(i2c, aht10_id);
  *              AHT10/AHT20
  *   @crc8: crc8 support flag
  *   @meas_size: measurements data size
+ *   @init_cmd: Initialization command
  */
 
 struct aht10_data {
@@ -92,6 +96,7 @@ struct aht10_data {
 	int humidity;
 	bool crc8;
 	unsigned int meas_size;
+	u8 init_cmd;
 };
 
 /*
@@ -101,13 +106,13 @@ struct aht10_data {
  */
 static int aht10_init(struct aht10_data *data)
 {
-	const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
+	const u8 cmd_init[] = {data->init_cmd, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
 			       0x00};
 	int res;
 	u8 status;
 	struct i2c_client *client = data->client;
 
-	res = i2c_master_send(client, cmd_init, 3);
+	res = i2c_master_send(client, cmd_init, sizeof(cmd_init));
 	if (res < 0)
 		return res;
 
@@ -352,9 +357,17 @@ static int aht10_probe(struct i2c_client *client)
 		data->meas_size = AHT20_MEAS_SIZE;
 		data->crc8 = true;
 		crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
+		data->init_cmd = AHT10_CMD_INIT;
+		break;
+	case dht20:
+		data->meas_size = AHT20_MEAS_SIZE;
+		data->crc8 = true;
+		crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
+		data->init_cmd = DHT20_CMD_INIT;
 		break;
 	default:
 		data->meas_size = AHT10_MEAS_SIZE;
+		data->init_cmd = AHT10_CMD_INIT;
 		break;
 	}
 
-- 
2.34.1