On Thu, 19 Feb 2015, Martin Fuzzey wrote:
> Many of the hardware configuration registers may only be modified while the
> device is inactive.
>
> Currently the probe code first activates the device and then modifies the
> registers (eg to set the scale). This doesn't actually work but is not
> noticed since the scale used is the default value.
>
> While at it also issue a hardware reset command at probe time.
comment below
> Signed-off-by: Martin Fuzzey <mfuzzey@xxxxxxxxxxx>
> ---
> drivers/iio/accel/mma8452.c | 39 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
> index 3c12d49..04a4f34 100644
> --- a/drivers/iio/accel/mma8452.c
> +++ b/drivers/iio/accel/mma8452.c
> @@ -32,6 +32,7 @@
> #define MMA8452_OFF_Z 0x31
> #define MMA8452_CTRL_REG1 0x2a
> #define MMA8452_CTRL_REG2 0x2b
> +#define MMA8452_CTRL_REG2_RST BIT(6)
>
> #define MMA8452_STATUS_DRDY (BIT(2) | BIT(1) | BIT(0))
>
> @@ -111,7 +112,7 @@ static const int mma8452_samp_freq[8][2] = {
> {6, 250000}, {1, 560000}
> };
>
> -/*
> +/*
> * Hardware has fullscale of -2G, -4G, -8G corresponding to raw value -2048
> * The userspace interface uses m/s^2 and we declare micro units
> * So scale factor is given by:
> @@ -335,6 +336,30 @@ static const struct iio_info mma8452_info = {
>
> static const unsigned long mma8452_scan_masks[] = {0x7, 0};
>
> +static int mma8452_reset(struct i2c_client *client)
> +{
> + int i;
> + int ret;
> +
> + ret = i2c_smbus_write_byte_data(client, MMA8452_CTRL_REG2,
> + MMA8452_CTRL_REG2_RST);
> + if (ret)
maybe ret < 0 for consistency
> + return ret;
> +
> + for (i = 0; i < 10; i++) {
> + udelay(100);
> + ret = i2c_smbus_read_byte_data(client, MMA8452_CTRL_REG2);
> + if (ret == -EIO)
> + continue; /* I2C comm reset */
> + if (ret < 0)
> + return ret;
> + if (!(ret & MMA8452_CTRL_REG2_RST))
> + return 0;
> + }
> +
> + return -ETIMEDOUT;
> +}
> +
> static int mma8452_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> @@ -365,10 +390,7 @@ static int mma8452_probe(struct i2c_client *client,
> indio_dev->num_channels = ARRAY_SIZE(mma8452_channels);
> indio_dev->available_scan_masks = mma8452_scan_masks;
>
> - data->ctrl_reg1 = MMA8452_CTRL_ACTIVE |
> - (MMA8452_CTRL_DR_DEFAULT << MMA8452_CTRL_DR_SHIFT);
> - ret = i2c_smbus_write_byte_data(client, MMA8452_CTRL_REG1,
> - data->ctrl_reg1);
> + ret = mma8452_reset(client);
> if (ret < 0)
> return ret;
>
> @@ -378,6 +400,13 @@ static int mma8452_probe(struct i2c_client *client,
> if (ret < 0)
> return ret;
>
> + data->ctrl_reg1 = MMA8452_CTRL_ACTIVE |
> + (MMA8452_CTRL_DR_DEFAULT << MMA8452_CTRL_DR_SHIFT);
> + ret = i2c_smbus_write_byte_data(client, MMA8452_CTRL_REG1,
> + data->ctrl_reg1);
> + if (ret < 0)
> + return ret;
> +
> ret = iio_triggered_buffer_setup(indio_dev, NULL,
> mma8452_trigger_handler, NULL);
> if (ret < 0)
>
> --
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>
--
Peter Meerwald
+43-664-2444418 (mobile)
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