[PATCH 4.7 077/184] iio: accel: bmc150: reset chip at init time

[Greg Kroah-Hartman]

4.7-stable review patch.  If anyone has any objections, please let me know.

--

From: Olof Johansson 

commit 1c500840934a138bd6b13556c210516e9301fbee upstream.

In at least one known setup, the chip comes up in a state where reading
the chip ID returns garbage unless it's been reset, due to noise on the
wires during system boot.

All supported chips have the same reset method, and based on the
datasheets they all need 1.3 or 1.8ms to recover after reset. So, do
the conservative thing here and always reset the chip.

Signed-off-by: Olof Johansson 
Reviewed-by: Srinivas Pandruvada 
Signed-off-by: Jonathan Cameron 
Signed-off-by: Greg Kroah-Hartman 

---
 drivers/iio/accel/bmc150-accel-core.c |   11 +++
 1 file changed, 11 insertions(+)

--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -67,6 +67,9 @@
 #define BMC150_ACCEL_REG_PMU_BW0x10
 #define BMC150_ACCEL_DEF_BW125
 
+#define BMC150_ACCEL_REG_RESET 0x14
+#define BMC150_ACCEL_RESET_VAL 0xB6
+
 #define BMC150_ACCEL_REG_INT_MAP_0 0x19
 #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE   BIT(2)
 
@@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct
int ret, i;
unsigned int val;
 
+   /*
+* Reset chip to get it in a known good state. A delay of 1.8ms after
+* reset is required according to the data sheets of supported chips.
+*/
+   regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
+BMC150_ACCEL_RESET_VAL);
+   usleep_range(1800, 2500);
+
ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID, );
if (ret < 0) {
dev_err(dev, "Error: Reading chip id\n");

[PATCH 4.7 077/184] iio: accel: bmc150: reset chip at init time

[Greg Kroah-Hartman]

4.7-stable review patch.  If anyone has any objections, please let me know.

--

From: Olof Johansson 

commit 1c500840934a138bd6b13556c210516e9301fbee upstream.

In at least one known setup, the chip comes up in a state where reading
the chip ID returns garbage unless it's been reset, due to noise on the
wires during system boot.

All supported chips have the same reset method, and based on the
datasheets they all need 1.3 or 1.8ms to recover after reset. So, do
the conservative thing here and always reset the chip.

Signed-off-by: Olof Johansson 
Reviewed-by: Srinivas Pandruvada 
Signed-off-by: Jonathan Cameron 
Signed-off-by: Greg Kroah-Hartman 

---
 drivers/iio/accel/bmc150-accel-core.c |   11 +++
 1 file changed, 11 insertions(+)

--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -67,6 +67,9 @@
 #define BMC150_ACCEL_REG_PMU_BW0x10
 #define BMC150_ACCEL_DEF_BW125
 
+#define BMC150_ACCEL_REG_RESET 0x14
+#define BMC150_ACCEL_RESET_VAL 0xB6
+
 #define BMC150_ACCEL_REG_INT_MAP_0 0x19
 #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE   BIT(2)
 
@@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct
int ret, i;
unsigned int val;
 
+   /*
+* Reset chip to get it in a known good state. A delay of 1.8ms after
+* reset is required according to the data sheets of supported chips.
+*/
+   regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
+BMC150_ACCEL_RESET_VAL);
+   usleep_range(1800, 2500);
+
ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID, );
if (ret < 0) {
dev_err(dev, "Error: Reading chip id\n");