iio: accel: bmc150: reset chip at init time

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 <olof@lixom.net>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
index bf17aae66145..59b380dbf27f 100644
--- 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_BW         0x10
 #define BMC150_ACCEL_DEF_BW                     125
 
+#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 bmc150_accel_data *data)
         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, &val);
         if (ret < 0) {
                 dev_err(dev, "Error: Reading chip id\n");