[PATCH linux dev-4.10 1/2] drivers/iio: dps310 Temperature measurement fix.

[Christopher Bostic]

Add a manufacturer's suggested workaround to deal with early revisions
of chip that don't indicate correct temperature.  Readings can be in the
~60C range when they should be in the ~20's.

Signed-off-by: Christopher Bostic <cbostic at linux.vnet.ibm.com>
---
 drivers/iio/pressure/dps310.c | 49 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 1b54ae0..f351c26 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -56,7 +56,12 @@
 #define  DPS310_FIFO_EN		BIT(5)
 #define  DPS310_SPI_EN		BIT(6)
 #define DPS310_RESET		0x0c
+#define DPS310_TEMP_FIX_E	0x0e
+#define DPS310_TEMP_FIX_F	0x0f
 #define  DPS310_RESET_MAGIC	(BIT(0) | BIT(3))
+#define DPS310_TEMP_FIX_32	0x32
+#define  DPS310_TEMP_ERR_FIXED	BIT(1)
+#define DPS310_TEMP_FIX_62	0x62
 #define DPS310_COEF_BASE	0x10
 
 #define DPS310_PRS_BASE		DPS310_PRS_B0
@@ -219,6 +224,9 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
 	case DPS310_MEAS_CFG:
 	case DPS310_CFG_REG:
 	case DPS310_RESET:
+	case DPS310_TEMP_FIX_E:
+	case DPS310_TEMP_FIX_F:
+	case DPS310_TEMP_FIX_62:
 		return true;
 	default:
 		return false;
@@ -308,7 +316,7 @@ static int dps310_read_raw(struct iio_dev *iio,
 	.writeable_reg = dps310_is_writeable_reg,
 	.volatile_reg = dps310_is_volatile_reg,
 	.cache_type = REGCACHE_RBTREE,
-	.max_register = 0x29,
+	.max_register = 0x62,
 };
 
 static const struct iio_info dps310_info = {
@@ -317,6 +325,41 @@ static int dps310_read_raw(struct iio_dev *iio,
 	.write_raw = dps310_write_raw,
 };
 
+/*
+ * Some verions of chip will read temperatures in the ~60C range when
+ * its acutally ~20C. This is the manufacturer recommended workaround
+ * to correct the issue.
+ */
+static int dps310_temp_workaround(struct dps310_data *data)
+{
+	int r, reg;
+
+	r = regmap_read(data->regmap, DPS310_TEMP_FIX_32, &reg);
+	if (r < 0)
+		return r;
+
+	if (!(reg & DPS310_TEMP_ERR_FIXED)) {
+		r = regmap_write(data->regmap, DPS310_TEMP_FIX_E, 0xA5);
+		if (r < 0)
+			return r;
+
+		r = regmap_write(data->regmap, DPS310_TEMP_FIX_F, 0x96);
+		if (r < 0)
+			return r;
+
+		r = regmap_write(data->regmap, DPS310_TEMP_FIX_62, 0x02);
+		if (r < 0)
+			return r;
+
+		r = regmap_write(data->regmap, DPS310_TEMP_FIX_E, 0x00);
+		if (r < 0)
+			return r;
+
+		r = regmap_write(data->regmap, DPS310_TEMP_FIX_F, 0x00);
+	}
+	return r;
+}
+
 static int dps310_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
@@ -379,6 +422,10 @@ static int dps310_probe(struct i2c_client *client,
 	if (r < 0)
 		return r;
 
+	r = dps310_temp_workaround(data);
+	if (r < 0)
+		return r;
+
 	r = devm_iio_device_register(&client->dev, iio);
 	if (r)
 		return r;
-- 
1.8.2.2