Commit dafcf4ed authored by Gwendal Grignou's avatar Gwendal Grignou Committed by Jonathan Cameron
Browse files

iio: hrtimer: Allow sub Hz granularity 



Allow setting frequency below 1Hz or sub 1Hz precision.
Useful for slow sensors like ALS.

Test frequency is set properly:
modprobe iio-trig-hrtimer && \
mkdir /sys/kernel/config/iio/triggers/hrtimer/t1 && \
cd /sys/bus/iio/devices/triggerX ;
for i in 1 .1 .01 .001 ; do
  echo $i > sampling_frequency
  cat sampling_frequency
done

Signed-off-by: default avatarGwendal Grignou <gwendal@chromium.org>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210226014733.2108544-1-gwendal@chromium.org


Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent 7b3589f4

Documentation/iio/iio_configfs.rst

+1 −0
Original line number Diff line number Diff line
@@ -99,3 +99,4 @@ Each trigger can have one or more attributes specific to the trigger type. 


"hrtimer" trigger type doesn't have any configurable attribute from /config dir.

It does introduce the sampling_frequency attribute to trigger directory.

That attribute sets the polling frequency in Hz, with mHz precision.

drivers/iio/trigger/iio-trig-hrtimer.c

+23 −10
Original line number Diff line number Diff line
@@ -16,13 +16,16 @@ 
#include <linux/iio/trigger.h>

#include <linux/iio/sw_trigger.h>



/* Defined locally, not in time64.h yet. */

#define PSEC_PER_SEC   1000000000000LL



/* default sampling frequency - 100Hz */

#define HRTIMER_DEFAULT_SAMPLING_FREQUENCY 100



struct iio_hrtimer_info {

	struct iio_sw_trigger swt;

	struct hrtimer timer;

	unsigned long sampling_frequency;

	int sampling_frequency[2];

	ktime_t period;

};
@@ -38,7 +41,9 @@ ssize_t iio_hrtimer_show_sampling_frequency(struct device *dev, 
	struct iio_trigger *trig = to_iio_trigger(dev);

	struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);



	return snprintf(buf, PAGE_SIZE, "%lu\n", info->sampling_frequency);

	return iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO,

			ARRAY_SIZE(info->sampling_frequency),

			info->sampling_frequency);

}



static
@@ -48,18 +53,26 @@ ssize_t iio_hrtimer_store_sampling_frequency(struct device *dev, 
{

	struct iio_trigger *trig = to_iio_trigger(dev);

	struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);

	unsigned long val;

	int ret;

	unsigned long long val;

	u64 period;

	int integer, fract, ret;



	ret = kstrtoul(buf, 10, &val);

	ret = iio_str_to_fixpoint(buf, 100, &integer, &fract);

	if (ret)

		return ret;

	if (integer < 0 || fract < 0)

		return -ERANGE;



	val = fract + 1000 * integer;  /* mHz */



	if (!val || val > NSEC_PER_SEC)

	if (!val || val > UINT_MAX)

		return -EINVAL;



	info->sampling_frequency = val;

	info->period = NSEC_PER_SEC / val;

	info->sampling_frequency[0] = integer;  /* Hz */

	info->sampling_frequency[1] = fract * 1000;  /* uHz */

	period = PSEC_PER_SEC;

	do_div(period, val);

	info->period = period;  /* nS */



	return len;

}
@@ -135,8 +148,8 @@ static struct iio_sw_trigger *iio_trig_hrtimer_probe(const char *name) 
	hrtimer_init(&trig_info->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);

	trig_info->timer.function = iio_hrtimer_trig_handler;



	trig_info->sampling_frequency = HRTIMER_DEFAULT_SAMPLING_FREQUENCY;

	trig_info->period = NSEC_PER_SEC / trig_info->sampling_frequency;

	trig_info->sampling_frequency[0] = HRTIMER_DEFAULT_SAMPLING_FREQUENCY;

	trig_info->period = NSEC_PER_SEC / trig_info->sampling_frequency[0];



	ret = iio_trigger_register(trig_info->swt.trigger);

	if (ret)