From dafcf4ed8392476099c9e95642d2daa6e61ee1b6 Mon Sep 17 00:00:00 2001
From: Gwendal Grignou <gwendal@chromium.org>
Date: Thu, 25 Feb 2021 17:47:33 -0800
Subject: [PATCH] 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>
---
Documentation/iio/iio_configfs.rst | 1 +
drivers/iio/trigger/iio-trig-hrtimer.c | 33 ++++++++++++++++++--------
2 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/Documentation/iio/iio_configfs.rst b/Documentation/iio/iio_configfs.rst
index dbc61f35ea051..b276397af797e 100644
--- a/Documentation/iio/iio_configfs.rst
+++ b/Documentation/iio/iio_configfs.rst
@@ -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.
diff --git a/drivers/iio/trigger/iio-trig-hrtimer.c b/drivers/iio/trigger/iio-trig-hrtimer.c
index 410de837d0417..aa8cc7391a60d 100644
--- a/drivers/iio/trigger/iio-trig-hrtimer.c
+++ b/drivers/iio/trigger/iio-trig-hrtimer.c
@@ -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)
--
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