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SubjectRe: [v2 5/8] iio: adc: aspeed: Add func to set sampling rate.
On Fri, 23 Jul 2021 16:16:18 +0800
Billy Tsai <billy_tsai@aspeedtech.com> wrote:

> Add the function to set the sampling rate and keep the sampling period
> for a driver used to wait the lastest value.
>
> Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
A few follow on comments from suggestion in early patch, but otherwise this
looks good to me.

Jonathan

> ---
> drivers/iio/adc/aspeed_adc.c | 48 +++++++++++++++++++++++++-----------
> 1 file changed, 33 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
> index 84f079195375..bb6100228cae 100644
> --- a/drivers/iio/adc/aspeed_adc.c
> +++ b/drivers/iio/adc/aspeed_adc.c
> @@ -55,6 +55,12 @@
>
> #define ASPEED_ADC_INIT_POLLING_TIME 500
> #define ASPEED_ADC_INIT_TIMEOUT 500000
> +/*
> + * When the sampling rate is too high, the ADC may not have enough charging
> + * time, resulting in a low voltage value. Thus, default use slow sampling
> + * rate for most user case.
> + */
> +#define ASPEED_ADC_DEF_SAMPLING_RATE 65000
>
> enum aspeed_adc_version {
> aspeed_adc_ast2400,
> @@ -77,6 +83,7 @@ struct aspeed_adc_data {
> struct clk_hw *clk_scaler;
> struct reset_control *rst;
> int vref;
> + u32 sample_period_ns;
> };
>
> #define ASPEED_CHAN(_idx, _data_reg_addr) { \
> @@ -108,6 +115,26 @@ static const struct iio_chan_spec aspeed_adc_iio_channels[] = {
> ASPEED_CHAN(15, 0x2E),
> };
>
> +static int aspeed_adc_set_sampling_rate(struct iio_dev *indio_dev, u32 rate)
> +{
> + struct aspeed_adc_data *data = iio_priv(indio_dev);
> + const struct aspeed_adc_model_data *model_data =
> + of_device_get_match_data(data->dev);

As in previous patch, this would be cleaner if there was a cached copy of
the model_data pointer in data rather than looking it up each time.

> +
> + if (rate < model_data->min_sampling_rate ||
> + rate > model_data->max_sampling_rate)
> + return -EINVAL;
> + /* Each sampling needs 12 clocks to covert.*/
> + clk_set_rate(data->clk_scaler->clk, rate * ASPEED_CLOCKS_PER_SAMPLE);
> +
> + rate = clk_get_rate(data->clk_scaler->clk);
> + data->sample_period_ns = DIV_ROUND_UP_ULL(
> + (u64)NSEC_PER_SEC * ASPEED_CLOCKS_PER_SAMPLE, rate);
> + dev_dbg(data->dev, "Adc clock = %d sample period = %d ns", rate,
> + data->sample_period_ns);

blank line here.

> + return 0;
> +}
> +
> static int aspeed_adc_read_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan,
> int *val, int *val2, long mask)
> @@ -138,19 +165,9 @@ static int aspeed_adc_write_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan,
> int val, int val2, long mask)
> {
> - struct aspeed_adc_data *data = iio_priv(indio_dev);
> - const struct aspeed_adc_model_data *model_data =
> - of_device_get_match_data(data->dev);
> -
> switch (mask) {
> case IIO_CHAN_INFO_SAMP_FREQ:
> - if (val < model_data->min_sampling_rate ||
> - val > model_data->max_sampling_rate)
> - return -EINVAL;
> -
> - clk_set_rate(data->clk_scaler->clk,
> - val * ASPEED_CLOCKS_PER_SAMPLE);
> - return 0;
> + return aspeed_adc_set_sampling_rate(indio_dev, val);
>
> case IIO_CHAN_INFO_SCALE:
> case IIO_CHAN_INFO_RAW:
> @@ -302,6 +319,10 @@ static int aspeed_adc_probe(struct platform_device *pdev)
> goto reset_error;
> }
> reset_control_deassert(data->rst);
> + ret = clk_prepare_enable(data->clk_scaler->clk);
> + if (ret)
> + goto clk_enable_error;
> + aspeed_adc_set_sampling_rate(indio_dev, ASPEED_ADC_DEF_SAMPLING_RATE);
>
> ret = aspeed_adc_vref_config(pdev);
> if (ret)
> @@ -327,9 +348,6 @@ static int aspeed_adc_probe(struct platform_device *pdev)
> goto poll_timeout_error;
> }
>
> - ret = clk_prepare_enable(data->clk_scaler->clk);
> - if (ret)
> - goto clk_enable_error;
> adc_engine_control_reg_val =
> readl(data->base + ASPEED_REG_ENGINE_CONTROL);
> /* Start all channels in normal mode. */
> @@ -354,8 +372,8 @@ static int aspeed_adc_probe(struct platform_device *pdev)
> iio_register_error:
> writel(ASPEED_ADC_OPERATION_MODE_POWER_DOWN,
> data->base + ASPEED_REG_ENGINE_CONTROL);
> - clk_disable_unprepare(data->clk_scaler->clk);
> vref_config_error:
> + clk_disable_unprepare(data->clk_scaler->clk);
> clk_enable_error:
> poll_timeout_error:
> reset_control_assert(data->rst);

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