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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>
This commit is contained in:
Quentin Schulz 2017-03-21 16:52:14 +01:00 committed by Jonathan Cameron
parent a096926ed4
commit 4bdc902968
1 changed files with 12 additions and 0 deletions
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12
drivers/iio/gyro/bmg160_core.c
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@ -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");