linux-kernel - Re: [PATCH V2 1/6] iio: accel: bmi088: Modified the scale calculate

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Message-ID: <20220514163235.6c6ae0f3@jic23-huawei>
Date:   Sat, 14 May 2022 16:32:35 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     LI Qingwu <Qing-wu.Li@...ca-geosystems.com.cn>
Cc:     lars@...afoo.de, mchehab+huawei@...nel.org, ardeleanalex@...il.com,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        robh+dt@...nel.org, mike.looijmans@...ic.nl,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V2 1/6] iio: accel: bmi088: Modified the scale calculate

On Tue, 10 May 2022 14:17:48 +0000
LI Qingwu <Qing-wu.Li@...ca-geosystems.com.cn> wrote:

> The units after application of scale are 100*m/s^2,
> The scale calculation is only for the device
> with the range of 3, 6, 12, and 24g,
> but some other chips have a range of 2, 4, 6, and 8g.
> 
> Modified the formula to a scale list.
> The scales in the list are calculated by 1/sensitivity*9.8.
> The new units after the application of scale are m/s^2.
> 
> Signed-off-by: LI Qingwu <Qing-wu.Li@...ca-geosystems.com.cn>
> ---
>  drivers/iio/accel/bmi088-accel-core.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/accel/bmi088-accel-core.c b/drivers/iio/accel/bmi088-accel-core.c
> index a06dae5c971d..9300313b63cb 100644
> --- a/drivers/iio/accel/bmi088-accel-core.c
> +++ b/drivers/iio/accel/bmi088-accel-core.c
> @@ -119,6 +119,7 @@ struct bmi088_accel_chip_info {
>  	u8 chip_id;
>  	const struct iio_chan_spec *channels;
>  	int num_channels;
> +	const int scale_table[4][2];
>  };
>  
>  struct bmi088_accel_data {
> @@ -280,6 +281,7 @@ static int bmi088_accel_read_raw(struct iio_dev *indio_dev,
>  	struct bmi088_accel_data *data = iio_priv(indio_dev);
>  	struct device *dev = regmap_get_device(data->regmap);
>  	int ret;
> +	int reg;
>  
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
> @@ -330,13 +332,12 @@ static int bmi088_accel_read_raw(struct iio_dev *indio_dev,
>  				return ret;
>  
>  			ret = regmap_read(data->regmap,
> -					  BMI088_ACCEL_REG_ACC_RANGE, val);
> +					  BMI088_ACCEL_REG_ACC_RANGE, &reg);
>  			if (ret)
>  				goto out_read_raw_pm_put;
> -
> -			*val2 = 15 - (*val & 0x3);
> -			*val = 3 * 980;
> -			ret = IIO_VAL_FRACTIONAL_LOG2;
> +			*val = data->chip_info->scale_table[reg&0x03][0];
> +			*val2 = data->chip_info->scale_table[reg&0x03][1];

Spaces needed around the &
The 0x03 should be a define - something like BMIO088_ACCEL_ACC_RANGE_MSK

Also, this driver doesn't yet use FIELD_PREP() / FIELD_GET()
but this is a good example of where using FIELD_GET() will make the logic
clearer.


> +			ret = IIO_VAL_INT_PLUS_MICRO;
>  
>  			goto out_read_raw_pm_put;
>  		default:
> @@ -432,6 +433,7 @@ static const struct bmi088_accel_chip_info bmi088_accel_chip_info_tbl[] = {
>  		.chip_id = 0x1E,
>  		.channels = bmi088_accel_channels,
>  		.num_channels = ARRAY_SIZE(bmi088_accel_channels),
> +		.scale_table = {{0, 897}, {0, 1795}, {0, 3590}, {0, 7179}},
>  	},
>  };
>