Re: [PATCH] iio: accel: st_accel: fix LIS3LV02 reading and scaling

[Jonathan Cameron <jic23@kernel.org>]

On 30/12/16 22:54, Linus Walleij wrote:
> The LIS3LV02 has a special bit that need to be set to get the
> read values left aligned. Before this patch we get gibberish
> like this:
> 
> iio_generic_buffer -a -c10 -n lis3lv02dl_accel
> (...)
> 0.000000 -0.010042 -0.642688 19155832931907
> 0.000000 -0.010042 -0.642688 19155858751073
> 
> Which is because we read a raw value for 1g as 64 which is
> the nominal 1024 for 1g shifted 4 bits to the left by being
> right-aligned rather than left aligned.
> 
> Since all other sensors are left aligned, add some code to
> set the special DAS (data alignment setting) bit to 1 so that
> the right value is now read like this:
> 
> iio_generic_buffer -a -c10 -n lis3lv02dl_accel
> (...)
> 0.000000 -0.147095 -10.120135 24761614364956
> -0.029419 -0.176514 -10.120135 24761631624540
> 
> The scaling was weird as well: we have a gain of 1000 for 1g
> and 3000 for 6g. I don't even remember how I came up with the
> old values but they are wrong.
> 
> Fixes: 3acddf74f807 ("iio: st-sensors: add support for lis3lv02d accelerometer")
> Cc: Lorenzo Bianconi <lorenzo.bianconi@st.com>
> Cc: Giuseppe Barba <giuseppe.barba@st.com>
> Cc: Denis Ciocca <denis.ciocca@st.com>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> I wouldn't bother with stable-tagging this, but queueuing for
> fixes would be nice. I plan to phase over the old misc driver
> to this later.
Fine by me. Applied to the fixes-togreg post rc1 branch of iio.git.
Will do a pull request in a few mins after checking for any other last
minute fixes.

Jonathan
> ---
>  drivers/iio/accel/st_accel_core.c               | 12 ++++++++++--
>  drivers/iio/common/st_sensors/st_sensors_core.c |  9 +++++++++
>  include/linux/iio/common/st_sensors.h           | 12 ++++++++++++
>  3 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/accel/st_accel_core.c b/drivers/iio/accel/st_accel_core.c
> index f6b6d42385e1..784670e2736b 100644
> --- a/drivers/iio/accel/st_accel_core.c
> +++ b/drivers/iio/accel/st_accel_core.c
> @@ -353,12 +353,12 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
>  				[0] = {
>  					.num = ST_ACCEL_FS_AVL_2G,
>  					.value = 0x00,
> -					.gain = IIO_G_TO_M_S_2(1024),
> +					.gain = IIO_G_TO_M_S_2(1000),
>  				},
>  				[1] = {
>  					.num = ST_ACCEL_FS_AVL_6G,
>  					.value = 0x01,
> -					.gain = IIO_G_TO_M_S_2(340),
> +					.gain = IIO_G_TO_M_S_2(3000),
>  				},
>  			},
>  		},
> @@ -366,6 +366,14 @@ static const struct st_sensor_settings st_accel_sensors_settings[] = {
>  			.addr = 0x21,
>  			.mask = 0x40,
>  		},
> +		/*
> +		 * Data Alignment Setting - needs to be set to get
> +		 * left-justified data like all other sensors.
> +		 */
> +		.das = {
> +			.addr = 0x21,
> +			.mask = 0x01,
> +		},
>  		.drdy_irq = {
>  			.addr = 0x21,
>  			.mask_int1 = 0x04,
> diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
> index d5cf7f31eaf9..79c8c7cd70d5 100644
> --- a/drivers/iio/common/st_sensors/st_sensors_core.c
> +++ b/drivers/iio/common/st_sensors/st_sensors_core.c
> @@ -401,6 +401,15 @@ int st_sensors_init_sensor(struct iio_dev *indio_dev,
>  			return err;
>  	}
>  
> +	/* set DAS */
> +	if (sdata->sensor_settings->das.addr) {
> +		err = st_sensors_write_data_with_mask(indio_dev,
> +					sdata->sensor_settings->das.addr,
> +					sdata->sensor_settings->das.mask, 1);
> +		if (err < 0)
> +			return err;
> +	}
> +
>  	if (sdata->int_pin_open_drain) {
>  		dev_info(&indio_dev->dev,
>  			 "set interrupt line to open drain mode\n");
> diff --git a/include/linux/iio/common/st_sensors.h b/include/linux/iio/common/st_sensors.h
> index 228bd44efa4c..497f2b3a5a62 100644
> --- a/include/linux/iio/common/st_sensors.h
> +++ b/include/linux/iio/common/st_sensors.h
> @@ -116,6 +116,16 @@ struct st_sensor_bdu {
>  };
>  
>  /**
> + * struct st_sensor_das - ST sensor device data alignment selection
> + * @addr: address of the register.
> + * @mask: mask to write the das flag for left alignment.
> + */
> +struct st_sensor_das {
> +	u8 addr;
> +	u8 mask;
> +};
> +
> +/**
>   * struct st_sensor_data_ready_irq - ST sensor device data-ready interrupt
>   * @addr: address of the register.
>   * @mask_int1: mask to enable/disable IRQ on INT1 pin.
> @@ -185,6 +195,7 @@ struct st_sensor_transfer_function {
>   * @enable_axis: Enable one or more axis of the sensor.
>   * @fs: Full scale register and full scale list available.
>   * @bdu: Block data update register.
> + * @das: Data Alignment Selection register.
>   * @drdy_irq: Data ready register of the sensor.
>   * @multi_read_bit: Use or not particular bit for [I2C/SPI] multi-read.
>   * @bootime: samples to discard when sensor passing from power-down to power-up.
> @@ -200,6 +211,7 @@ struct st_sensor_settings {
>  	struct st_sensor_axis enable_axis;
>  	struct st_sensor_fullscale fs;
>  	struct st_sensor_bdu bdu;
> +	struct st_sensor_das das;
>  	struct st_sensor_data_ready_irq drdy_irq;
>  	bool multi_read_bit;
>  	unsigned int bootime;
>