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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: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210226014733.2108544-1-gwendal@chromium.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Gwendal Grignou 2021-02-25 17:47:33 -08:00 committed by Jonathan Cameron
parent 7b3589f49b
commit dafcf4ed83
2 changed files with 24 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/iio/iio_configfs.rst
View File

@ -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.

33
drivers/iio/trigger/iio-trig-hrtimer.c
View File

@ -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;
if (!val || val > NSEC_PER_SEC)
val = fract + 1000 * integer; /* mHz */
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)