When the device is configured to Sinc5 filter and decimation x8,
output data is reduced to 16-bits in order to support 1 MHz of
sampling frequency due to clock limitation.
Use multiple scan types feature to enable the driver to switch
scan type in runtime, making possible to support both 24-bit and
16-bit resolution.
Signed-off-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx>
---
drivers/iio/adc/ad7768-1.c | 65 ++++++++++++++++++++++++++++++++------
1 file changed, 56 insertions(+), 9 deletions(-)
diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 9741a6d47942..5e4e7d387f9a 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -134,6 +134,11 @@ struct ad7768_clk_configuration {
enum ad7768_pwrmode pwrmode;
};
+enum ad7768_scan_type {
+ AD7768_SCAN_TYPE_NORMAL,
+ AD7768_SCAN_TYPE_HIGH_SPEED,
+};
+
static const char * const ad7768_vcm_modes[] = {
"(AVDD1-AVSS)/2",
"2V5",
@@ -145,6 +150,10 @@ static const char * const ad7768_vcm_modes[] = {
"OFF",
};
+static const int ad7768_mclk_div_rates[4] = {
+ 16, 8, 4, 2,
+};
+
static const struct ad7768_clk_configuration ad7768_clk_config[] = {
{ AD7768_MCLK_DIV_2, AD7768_DEC_RATE_8, 16, AD7768_FAST_MODE },
{ AD7768_MCLK_DIV_2, AD7768_DEC_RATE_16, 32, AD7768_FAST_MODE },
@@ -159,6 +168,21 @@ static const struct ad7768_clk_configuration ad7768_clk_config[] = {
{ AD7768_MCLK_DIV_16, AD7768_DEC_RATE_1024, 16384, AD7768_ECO_MODE },
};
+static const struct iio_scan_type ad7768_scan_type[] = {
+ [AD7768_SCAN_TYPE_NORMAL] = {
+ .sign = 's',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_BE,
+ },
+ [AD7768_SCAN_TYPE_HIGH_SPEED] = {
+ .sign = 's',
+ .realbits = 16,
+ .storagebits = 32,
+ .endianness = IIO_BE,
+ },
+};
+
static int ad7768_get_vcm(struct iio_dev *dev, const struct iio_chan_spec *chan);
static int ad7768_set_vcm(struct iio_dev *dev, const struct iio_chan_spec *chan,
unsigned int mode);
@@ -190,13 +214,9 @@ static const struct iio_chan_spec ad7768_channels[] = {
.indexed = 1,
.channel = 0,
.scan_index = 0,
- .scan_type = {
- .sign = 's',
- .realbits = 24,
- .storagebits = 32,
- .shift = 8,
- .endianness = IIO_BE,
- },
+ .has_ext_scan_type = 1,
+ .ext_scan_type = ad7768_scan_type,
+ .num_ext_scan_type = ARRAY_SIZE(ad7768_scan_type),
},
};
@@ -208,6 +228,7 @@ struct ad7768_state {
struct gpio_chip gpiochip;
unsigned int gpio_avail_map;
unsigned int mclk_freq;
+ unsigned int dec_rate;
unsigned int samp_freq;
unsigned int common_mode_voltage;
struct completion completion;
@@ -308,6 +329,15 @@ static int ad7768_scan_direct(struct iio_dev *indio_dev)
ret = ad7768_spi_reg_read(st, AD7768_REG_ADC_DATA, &readval, 3);
if (ret < 0)
return ret;
+
+ /*
+ * When the decimation rate is set to x8, the ADC data precision is reduced
+ * from 24 bits to 16 bits. Since the AD7768_REG_ADC_DATA register provides
+ * 24-bit data, the precision is reduced by right-shifting the read value
+ * by 8 bits.
+ */
+ if (st->dec_rate == 8)
+ readval = readval >> 8;
/*
* Any SPI configuration of the AD7768-1 can only be
* performed in continuous conversion mode.
@@ -489,6 +519,8 @@ static int ad7768_set_freq(struct ad7768_state *st,
if (ret < 0)
return ret;
+ st->dec_rate = ad7768_clk_config[idx].clk_div /
+ ad7768_mclk_div_rates[ad7768_clk_config[idx].mclk_div];
st->samp_freq = DIV_ROUND_CLOSEST(st->mclk_freq,
ad7768_clk_config[idx].clk_div);
@@ -544,8 +576,13 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
int *val, int *val2, long info)
{
struct ad7768_state *st = iio_priv(indio_dev);
+ const struct iio_scan_type *scan_type;
int scale_uv, ret;
+ scan_type = iio_get_current_scan_type(indio_dev, chan);
+ if (IS_ERR(scan_type))
+ return PTR_ERR(scan_type);
+
switch (info) {
case IIO_CHAN_INFO_RAW:
ret = iio_device_claim_direct_mode(indio_dev);
@@ -554,7 +591,7 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
ret = ad7768_scan_direct(indio_dev);
if (ret >= 0)
- *val = sign_extend32(ret, chan->scan_type.realbits - 1);
+ *val = sign_extend32(ret, scan_type->realbits - 1);
iio_device_release_direct_mode(indio_dev);
if (ret < 0)
@@ -568,7 +605,7 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
return scale_uv;
*val = (scale_uv * 2) / 1000;
- *val2 = chan->scan_type.realbits;
+ *val2 = scan_type->realbits;
return IIO_VAL_FRACTIONAL_LOG2;
@@ -612,11 +649,21 @@ static const struct attribute_group ad7768_group = {
.attrs = ad7768_attributes,
};
+static int ad7768_get_current_scan_type(const struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan)
+{
+ struct ad7768_state *st = iio_priv(indio_dev);
+
+ return st->dec_rate == 8 ? AD7768_SCAN_TYPE_HIGH_SPEED :
+ AD7768_SCAN_TYPE_NORMAL;
+}
+
static const struct iio_info ad7768_info = {
.attrs = &ad7768_group,
.read_raw = &ad7768_read_raw,
.write_raw = &ad7768_write_raw,
.read_label = ad7768_read_label,
+ .get_current_scan_type = &ad7768_get_current_scan_type,
.debugfs_reg_access = &ad7768_reg_access,
};
--
2.34.1
