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SubjectRe: [PATCH v3 4/7] iio: imu: adis16480: Calculate the sampling frequency in a generic way
On Wed, 27 Feb 2019 18:14:25 +0200
Stefan Popa <stefan.popa@analog.com> wrote:

> The adis1648x devices have an internal clock of 2.46 kSPS. The sampling
> frequency is calculated by applying a decimation rate which can take the
> maximum value of 2047.
>
> Although all adis1648x devices are similar in this regard, devices that
> will use this feature will be added in the future.
>
> Signed-off-by: Stefan Popa <stefan.popa@analog.com>
Straight forward refactor so fine.

Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

A comment inline about something in the old code!

Thanks,

Jonathan

> ---
> drivers/iio/imu/adis16480.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/imu/adis16480.c b/drivers/iio/imu/adis16480.c
> index 5a2864a..92abc95 100644
> --- a/drivers/iio/imu/adis16480.c
> +++ b/drivers/iio/imu/adis16480.c
> @@ -125,6 +125,8 @@ struct adis16480_chip_info {
> unsigned int accel_max_val;
> unsigned int accel_max_scale;
> unsigned int temp_scale;
> + unsigned int int_clk;
> + unsigned int max_dec_rate;
> };
>
> enum adis16480_int_pin {
> @@ -299,9 +301,9 @@ static int adis16480_set_freq(struct iio_dev *indio_dev, int val, int val2)
> if (t <= 0)
> return -EINVAL;
>
> - t = 2460000 / t;
> - if (t > 2048)
> - t = 2048;
> + t = st->chip_info->int_clk / t;
> + if (t > st->chip_info->max_dec_rate)
> + t = st->chip_info->max_dec_rate;
>
> if (t != 0)
> t--;
> @@ -320,7 +322,7 @@ static int adis16480_get_freq(struct iio_dev *indio_dev, int *val, int *val2)
> if (ret < 0)
> return ret;
>
> - freq = 2460000 / (t + 1);
> + freq = st->chip_info->int_clk / (t + 1);

I'm a little curious about why t + 1? Presumably to avoid weird rounding
issues, but maybe a nice addition would be a comment explaining this.

> *val = freq / 1000;
> *val2 = (freq % 1000) * 1000;
>
> @@ -726,6 +728,8 @@ static const struct adis16480_chip_info adis16480_chip_info[] = {
> .accel_max_val = IIO_M_S_2_TO_G(21973),
> .accel_max_scale = 18,
> .temp_scale = 5650, /* 5.65 milli degree Celsius */
> + .int_clk = 2460000,
> + .max_dec_rate = 2048,
> },
> [ADIS16480] = {
> .channels = adis16480_channels,
> @@ -735,6 +739,8 @@ static const struct adis16480_chip_info adis16480_chip_info[] = {
> .accel_max_val = IIO_M_S_2_TO_G(12500),
> .accel_max_scale = 10,
> .temp_scale = 5650, /* 5.65 milli degree Celsius */
> + .int_clk = 2460000,
> + .max_dec_rate = 2048,
> },
> [ADIS16485] = {
> .channels = adis16485_channels,
> @@ -744,6 +750,8 @@ static const struct adis16480_chip_info adis16480_chip_info[] = {
> .accel_max_val = IIO_M_S_2_TO_G(20000),
> .accel_max_scale = 5,
> .temp_scale = 5650, /* 5.65 milli degree Celsius */
> + .int_clk = 2460000,
> + .max_dec_rate = 2048,
> },
> [ADIS16488] = {
> .channels = adis16480_channels,
> @@ -753,6 +761,8 @@ static const struct adis16480_chip_info adis16480_chip_info[] = {
> .accel_max_val = IIO_M_S_2_TO_G(22500),
> .accel_max_scale = 18,
> .temp_scale = 5650, /* 5.65 milli degree Celsius */
> + .int_clk = 2460000,
> + .max_dec_rate = 2048,
> },
> };
>

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