[RESEND v4 12/15] iio: adc: aspeed: Add func to set sampling rate.

Billy Tsai
2021-08-25T01:57:24Z

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>
---
drivers/iio/adc/aspeed_adc.c | 58 +++++++++++++++++++++++++-----------
1 file changed, 40 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
index 8fe7da1a651f..4d979dd7fe88 100644
--- a/drivers/iio/adc/aspeed_adc.c
+++ b/drivers/iio/adc/aspeed_adc.c
@@ -65,6 +65,12 @@

#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

struct aspeed_adc_model_data {
const char *model_name;
@@ -88,6 +94,7 @@ 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) { \
@@ -119,6 +126,24 @@ 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);
+
+ if (rate < data->model_data->min_sampling_rate ||
+ rate > data->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);
+
+ 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)
@@ -149,17 +174,10 @@ 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);

switch (mask) {
case IIO_CHAN_INFO_SAMP_FREQ:
- if (val < data->model_data->min_sampling_rate ||
- val > data->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:
@@ -386,6 +404,20 @@ static int aspeed_adc_probe(struct platform_device *pdev)
if (ret)
return ret;

+ ret = clk_prepare_enable(data->clk_scaler->clk);
+ if (ret)
+ return ret;
+
+ ret = devm_add_action_or_reset(data->dev,
+ aspeed_adc_clk_disable_unprepare,
+ data->clk_scaler->clk);
+ if (ret)
+ return ret;
+
+ ret = aspeed_adc_set_sampling_rate(indio_dev, ASPEED_ADC_DEF_SAMPLING_RATE);
+ if (ret)
+ return ret;
+
ret = aspeed_adc_vref_config(indio_dev);
if (ret)
return ret;
@@ -413,16 +445,6 @@ static int aspeed_adc_probe(struct platform_device *pdev)
}

/* Start all channels in normal mode. */
- ret = clk_prepare_enable(data->clk_scaler->clk);
- if (ret)
- return ret;
-
- ret = devm_add_action_or_reset(data->dev,
- aspeed_adc_clk_disable_unprepare,
- data->clk_scaler->clk);
- if (ret)
- return ret;
-
adc_engine_control_reg_val =
readl(data->base + ASPEED_REG_ENGINE_CONTROL);
adc_engine_control_reg_val |=