On Mon, 2016-08-29 at 18:23 +0100, Jonathan Cameron wrote:
> 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>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
> 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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