On 25/08/16 17:45, Olof Johansson wrote:
> 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@xxxxxxxxx>
Looks good to me.
Srinivas, it's your driver. Can you take a quick look at this?
Thanks,
Jonathan
> ---
> drivers/iio/accel/bmc150-accel-core.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> index bf17aae..59b380d 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");
>
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