X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=drivers%2Fhwmon%2Fads7828.c;h=ee396ff167d9d1c2070eeb254475d53dbe4a3f0a;hb=e46c9b02e2422e7b8f8a63ff53f1f8eddc23b247;hp=6c99ee7bafa3fdf47d6479b7198697ec835a23e8;hpb=b9e2c097efe19c3c04ea3d84b295748e39e96c2b;p=firefly-linux-kernel-4.4.55.git

diff --git a/drivers/hwmon/ads7828.c b/drivers/hwmon/ads7828.c
index 6c99ee7bafa3..ee396ff167d9 100644
--- a/drivers/hwmon/ads7828.c
+++ b/drivers/hwmon/ads7828.c
@@ -120,6 +120,7 @@ static int ads7828_probe(struct i2c_client *client,
 	unsigned int vref_mv = ADS7828_INT_VREF_MV;
 	bool diff_input = false;
 	bool ext_vref = false;
+	unsigned int regval;
 
 	data = devm_kzalloc(dev, sizeof(struct ads7828_data), GFP_KERNEL);
 	if (!data)
@@ -154,6 +155,15 @@ static int ads7828_probe(struct i2c_client *client,
 	if (!diff_input)
 		data->cmd_byte |= ADS7828_CMD_SD_SE;
 
+	/*
+	 * Datasheet specifies internal reference voltage is disabled by
+	 * default. The internal reference voltage needs to be enabled and
+	 * voltage needs to settle before getting valid ADC data. So perform a
+	 * dummy read to enable the internal reference voltage.
+	 */
+	if (!ext_vref)
+		regmap_read(data->regmap, data->cmd_byte, &regval);
+
 	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 							   data,
 							   ads7828_groups);