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iio: ina2xx: provide a sysfs parameter to allow async readout of the ADCs

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This can lead to repeated or skipped samples depending on the clock beat
between the capture thread and the chip sampling clock, but will also spare
reading/waiting for the Capture Ready Flag and improve the available i2c
bandwidth for reading measurements.

Output of iio_info:
...snip...
4 device-specific attributes found:
  attr 0: in_oversampling_ratio value: 4
  attr 1: in_allow_async_readout value: 0
  attr 2: integration_time_available value: 140 204 332 588 1100 2116...
  attr 3: in_sampling_frequency value: 114

Signed-off-by: Marc Titinger <mtitinger@baylibre.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Marc Titinger 2015-12-07 10:09:35 +01:00 committed by Jonathan Cameron
parent c43a102e67
commit f9993c0771
1 changed files with 45 additions and 9 deletions
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54
drivers/iio/adc/ina2xx-adc.c
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@ -116,6 +116,7 @@ struct ina2xx_chip_info {
s64 prev_ns; /* track buffer capture time, check for underruns*/
int int_time_vbus; /* Bus voltage integration time uS */
int int_time_vshunt; /* Shunt voltage integration time uS */
bool allow_async_readout;
};
static const struct ina2xx_config ina2xx_config[] = {
@ -322,6 +323,33 @@ _err:
}
static ssize_t ina2xx_allow_async_readout_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct ina2xx_chip_info *chip = iio_priv(dev_to_iio_dev(dev));
return sprintf(buf, "%d\n", chip->allow_async_readout);
}
static ssize_t ina2xx_allow_async_readout_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t len)
{
struct ina2xx_chip_info *chip = iio_priv(dev_to_iio_dev(dev));
bool val;
int ret;
ret = strtobool((const char *) buf, &val);
if (ret)
return ret;
chip->allow_async_readout = val;
return len;
}
#define INA2XX_CHAN(_type, _index, _address) { \
.type = (_type), \
.address = (_address), \
@ -390,16 +418,17 @@ static int ina2xx_work_buffer(struct iio_dev *indio_dev)
* GPIO a triggered buffer could be used instead.
* For now, we pay for that extra read of the ALERT register
*/
do {
ret = regmap_read(chip->regmap, INA226_ALERT_MASK,
&alert);
if (ret < 0)
return ret;
if (!chip->allow_async_readout)
do {
ret = regmap_read(chip->regmap, INA226_ALERT_MASK,
&alert);
if (ret < 0)
return ret;
alert &= INA266_CVRF;
trace_printk("Conversion ready: %d\n", !!alert);
alert &= INA266_CVRF;
trace_printk("Conversion ready: %d\n", !!alert);
} while (!alert);
} while (!alert);
/*
* Single register reads: bulk_read will not work with ina226
@ -444,7 +473,8 @@ static int ina2xx_capture_thread(void *data)
* Poll a bit faster than the chip internal Fs, in case
* we wish to sync with the conversion ready flag.
*/
sampling_us -= 200;
if (!chip->allow_async_readout)
sampling_us -= 200;
do {
buffer_us = ina2xx_work_buffer(indio_dev);
@ -469,6 +499,7 @@ static int ina2xx_buffer_enable(struct iio_dev *indio_dev)
1000000/sampling_us, chip->avg);
trace_printk("Expected work period: %u us\n", sampling_us);
trace_printk("Async readout mode: %d\n", chip->allow_async_readout);
chip->prev_ns = iio_get_time_ns();
@ -510,7 +541,12 @@ static int ina2xx_debug_reg(struct iio_dev *indio_dev,
static IIO_CONST_ATTR_INT_TIME_AVAIL \
("0.000140 0.000204 0.000332 0.000588 0.001100 0.002116 0.004156 0.008244");
static IIO_DEVICE_ATTR(in_allow_async_readout, S_IRUGO | S_IWUSR,
ina2xx_allow_async_readout_show,
ina2xx_allow_async_readout_store, 0);
static struct attribute *ina2xx_attributes[] = {
&iio_dev_attr_in_allow_async_readout.dev_attr.attr,
&iio_const_attr_integration_time_available.dev_attr.attr,
NULL,
};