iio: bmg160: reset chip when probing

The gyroscope chip might need to be reset to be used.

Without the chip being reset, the driver stopped at the first
regmap_read (to get the CHIP_ID) and failed to probe.

The datasheet of the gyroscope says that a minimum wait of 30ms after
the reset has to be done.

This patch has been checked on a BMX055 and the datasheet of the BMG160
and the BMI055 give the same reset register and bits.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/gyro/bmg160_core.c b/drivers/iio/gyro/bmg160_core.c
index f7fcfa886f72181e36b89b38daa327dbf8d17cd0..821919dd245bc8597ce901fffe26001382a9a71c 100644 (file)
--- a/drivers/iio/gyro/bmg160_core.c
+++ b/drivers/iio/gyro/bmg160_core.c
@@ -27,6 +27,7 @@
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
 #include <linux/regmap.h>
+#include <linux/delay.h>
 #include "bmg160.h"
 
 #define BMG160_IRQ_NAME                "bmg160_event"
@@ -52,6 +53,9 @@
 #define BMG160_DEF_BW                  100
 #define BMG160_REG_PMU_BW_RES          BIT(7)
 
+#define BMG160_GYRO_REG_RESET          0x14
+#define BMG160_GYRO_RESET_VAL          0xb6
+
 #define BMG160_REG_INT_MAP_0           0x17
 #define BMG160_INT_MAP_0_BIT_ANY       BIT(1)
 
@@ -236,6 +240,14 @@ static int bmg160_chip_init(struct bmg160_data *data)
        int ret;
        unsigned int val;
 
+       /*
+        * Reset chip to get it in a known good state. A delay of 30ms after
+        * reset is required according to the datasheet.
+        */
+       regmap_write(data->regmap, BMG160_GYRO_REG_RESET,
+                    BMG160_GYRO_RESET_VAL);
+       usleep_range(30000, 30700);
+
        ret = regmap_read(data->regmap, BMG160_REG_CHIP_ID, &val);
        if (ret < 0) {
                dev_err(dev, "Error reading reg_chip_id\n");