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Subject[PATCH v3 2/3] iio: dps310: Temperature measurement errata
Date
From: Christopher Bostic <cbostic@linux.vnet.ibm.com>

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>
---
drivers/iio/pressure/dps310.c | 52 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 9acfccb..a093e3a 100644
--- 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 void dps310_reset(void *action_data)
.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 void dps310_reset(void *action_data)
.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;
--
1.8.3.1
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