iio: dps310: Temperature measurement errata

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@linux.vnet.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 9acfccba1d5025f05d8e97100fef5c71ea362494..a093e3a156653c354a52ecf10b94bd9d71619073 100644 (file)
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -53,7 +53,6 @@
 #define DPS310_RESET           0x0c
 #define  DPS310_RESET_MAGIC    0x09
 #define DPS310_COEF_BASE       0x10
-#define DPS310_COEF_SRC                0x28
 
 /* Make sure sleep time is <= 20ms for usleep_range */
 #define DPS310_POLL_SLEEP_US(t)                min(20000, (t) / 8)
@@ -234,6 +233,10 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
        case DPS310_MEAS_CFG:
        case DPS310_CFG_REG:
        case DPS310_RESET:
+       /* No documentation available on the registers below */
+       case 0x0e:
+       case 0x0f:
+       case 0x62:
                return true;
        default:
                return false;
@@ -250,6 +253,7 @@ static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
        case DPS310_TMP_B1:
        case DPS310_TMP_B2:
        case DPS310_MEAS_CFG:
+       case 0x32:      /* No documentation available on this register */
                return true;
        default:
                return false;
@@ -360,7 +364,7 @@ static const struct regmap_config dps310_regmap_config = {
        .writeable_reg = dps310_is_writeable_reg,
        .volatile_reg = dps310_is_volatile_reg,
        .cache_type = REGCACHE_RBTREE,
-       .max_register = DPS310_COEF_SRC,
+       .max_register = 0x62, /* No documentation available on this register */
 };
 
 static const struct iio_info dps310_info = {
@@ -368,6 +372,46 @@ static const struct iio_info dps310_info = {
        .write_raw = dps310_write_raw,
 };
 
+/*
+ * Some verions of chip will read temperatures in the ~60C range when
+ * its actually ~20C. This is the manufacturer recommended workaround
+ * to correct the issue. The registers used below are undocumented.
+ */
+static int dps310_temp_workaround(struct dps310_data *data)
+{
+       int rc;
+       int reg;
+
+       rc = regmap_read(data->regmap, 0x32, &reg);
+       if (rc < 0)
+               return rc;
+
+       /*
+        * If bit 1 is set then the device is okay, and the workaround does not
+        * need to be applied
+        */
+       if (reg & BIT(1))
+               return 0;
+
+       rc = regmap_write(data->regmap, 0x0e, 0xA5);
+       if (rc < 0)
+               return rc;
+
+       rc = regmap_write(data->regmap, 0x0f, 0x96);
+       if (rc < 0)
+               return rc;
+
+       rc = regmap_write(data->regmap, 0x62, 0x02);
+       if (rc < 0)
+               return rc;
+
+       rc = regmap_write(data->regmap, 0x0e, 0x00);
+       if (rc < 0)
+               return rc;
+
+       return regmap_write(data->regmap, 0x0f, 0x00);
+}
+
 static int dps310_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
 {
@@ -439,6 +483,10 @@ static int dps310_probe(struct i2c_client *client,
        if (rc < 0)
                return rc;
 
+       rc = dps310_temp_workaround(data);
+       if (rc < 0)
+               return rc;
+
        rc = devm_iio_device_register(&client->dev, iio);
        if (rc)
                return rc;