iio:core: timestamping clock selection support

Adds a new per-device sysfs attribute "current_timestamp_clock" to allow
userspace to select a particular POSIX clock for buffered samples and
events timestamping.

Following clocks, as listed in clock_gettime(2), are supported:
CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_MONOTONIC_RAW,
CLOCK_REALTIME_COARSE, CLOCK_MONOTONIC_COARSE, CLOCK_BOOTTIME and
CLOCK_TAI.

Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Acked-by: Sanchayan Maity <maitysanchayan@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 175 insertions, 4 deletions

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 2a85bd888619..f914d5d140e4 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -178,6 +178,86 @@ ssize_t iio_read_const_attr(struct device *dev,
 }
 EXPORT_SYMBOL(iio_read_const_attr);
 
+static int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
+{
+	int ret;
+	const struct iio_event_interface *ev_int = indio_dev->event_interface;
+
+	ret = mutex_lock_interruptible(&indio_dev->mlock);
+	if (ret)
+		return ret;
+	if ((ev_int && iio_event_enabled(ev_int)) ||
+	    iio_buffer_enabled(indio_dev)) {
+		mutex_unlock(&indio_dev->mlock);
+		return -EBUSY;
+	}
+	indio_dev->clock_id = clock_id;
+	mutex_unlock(&indio_dev->mlock);
+
+	return 0;
+}
+
+/**
+ * iio_get_time_ns() - utility function to get a time stamp for events etc
+ * @indio_dev: device
+ */
+s64 iio_get_time_ns(const struct iio_dev *indio_dev)
+{
+	struct timespec tp;
+
+	switch (iio_device_get_clock(indio_dev)) {
+	case CLOCK_REALTIME:
+		ktime_get_real_ts(&tp);
+		break;
+	case CLOCK_MONOTONIC:
+		ktime_get_ts(&tp);
+		break;
+	case CLOCK_MONOTONIC_RAW:
+		getrawmonotonic(&tp);
+		break;
+	case CLOCK_REALTIME_COARSE:
+		tp = current_kernel_time();
+		break;
+	case CLOCK_MONOTONIC_COARSE:
+		tp = get_monotonic_coarse();
+		break;
+	case CLOCK_BOOTTIME:
+		get_monotonic_boottime(&tp);
+		break;
+	case CLOCK_TAI:
+		timekeeping_clocktai(&tp);
+		break;
+	default:
+		BUG();
+	}
+
+	return timespec_to_ns(&tp);
+}
+EXPORT_SYMBOL(iio_get_time_ns);
+
+/**
+ * iio_get_time_res() - utility function to get time stamp clock resolution in
+ *                      nano seconds.
+ * @indio_dev: device
+ */
+unsigned int iio_get_time_res(const struct iio_dev *indio_dev)
+{
+	switch (iio_device_get_clock(indio_dev)) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_RAW:
+	case CLOCK_BOOTTIME:
+	case CLOCK_TAI:
+		return hrtimer_resolution;
+	case CLOCK_REALTIME_COARSE:
+	case CLOCK_MONOTONIC_COARSE:
+		return LOW_RES_NSEC;
+	default:
+		BUG();
+	}
+}
+EXPORT_SYMBOL(iio_get_time_res);
+
 static int __init iio_init(void)
 {
 	int ret;
@@ -990,11 +1070,91 @@ static ssize_t iio_show_dev_name(struct device *dev,
 
 static DEVICE_ATTR(name, S_IRUGO, iio_show_dev_name, NULL);
 
+static ssize_t iio_show_timestamp_clock(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	const struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	const clockid_t clk = iio_device_get_clock(indio_dev);
+	const char *name;
+	ssize_t sz;
+
+	switch (clk) {
+	case CLOCK_REALTIME:
+		name = "realtime\n";
+		sz = sizeof("realtime\n");
+		break;
+	case CLOCK_MONOTONIC:
+		name = "monotonic\n";
+		sz = sizeof("monotonic\n");
+		break;
+	case CLOCK_MONOTONIC_RAW:
+		name = "monotonic_raw\n";
+		sz = sizeof("monotonic_raw\n");
+		break;
+	case CLOCK_REALTIME_COARSE:
+		name = "realtime_coarse\n";
+		sz = sizeof("realtime_coarse\n");
+		break;
+	case CLOCK_MONOTONIC_COARSE:
+		name = "monotonic_coarse\n";
+		sz = sizeof("monotonic_coarse\n");
+		break;
+	case CLOCK_BOOTTIME:
+		name = "boottime\n";
+		sz = sizeof("boottime\n");
+		break;
+	case CLOCK_TAI:
+		name = "tai\n";
+		sz = sizeof("tai\n");
+		break;
+	default:
+		BUG();
+	}
+
+	memcpy(buf, name, sz);
+	return sz;
+}
+
+static ssize_t iio_store_timestamp_clock(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t len)
+{
+	clockid_t clk;
+	int ret;
+
+	if (sysfs_streq(buf, "realtime"))
+		clk = CLOCK_REALTIME;
+	else if (sysfs_streq(buf, "monotonic"))
+		clk = CLOCK_MONOTONIC;
+	else if (sysfs_streq(buf, "monotonic_raw"))
+		clk = CLOCK_MONOTONIC_RAW;
+	else if (sysfs_streq(buf, "realtime_coarse"))
+		clk = CLOCK_REALTIME_COARSE;
+	else if (sysfs_streq(buf, "monotonic_coarse"))
+		clk = CLOCK_MONOTONIC_COARSE;
+	else if (sysfs_streq(buf, "boottime"))
+		clk = CLOCK_BOOTTIME;
+	else if (sysfs_streq(buf, "tai"))
+		clk = CLOCK_TAI;
+	else
+		return -EINVAL;
+
+	ret = iio_device_set_clock(dev_to_iio_dev(dev), clk);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static DEVICE_ATTR(current_timestamp_clock, S_IRUGO | S_IWUSR,
+		   iio_show_timestamp_clock, iio_store_timestamp_clock);
+
 static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 {
 	int i, ret = 0, attrcount, attrn, attrcount_orig = 0;
 	struct iio_dev_attr *p;
-	struct attribute **attr;
+	struct attribute **attr, *clk = NULL;
 
 	/* First count elements in any existing group */
 	if (indio_dev->info->attrs) {
@@ -1009,16 +1169,25 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 	 */
 	if (indio_dev->channels)
 		for (i = 0; i < indio_dev->num_channels; i++) {
-			ret = iio_device_add_channel_sysfs(indio_dev,
-							   &indio_dev
-							   ->channels[i]);
+			const struct iio_chan_spec *chan =
+				&indio_dev->channels[i];
+
+			if (chan->type == IIO_TIMESTAMP)
+				clk = &dev_attr_current_timestamp_clock.attr;
+
+			ret = iio_device_add_channel_sysfs(indio_dev, chan);
 			if (ret < 0)
 				goto error_clear_attrs;
 			attrcount += ret;
 		}
 
+	if (indio_dev->event_interface)
+		clk = &dev_attr_current_timestamp_clock.attr;
+
 	if (indio_dev->name)
 		attrcount++;
+	if (clk)
+		attrcount++;
 
 	indio_dev->chan_attr_group.attrs = kcalloc(attrcount + 1,
 						   sizeof(indio_dev->chan_attr_group.attrs[0]),
@@ -1039,6 +1208,8 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 		indio_dev->chan_attr_group.attrs[attrn++] = &p->dev_attr.attr;
 	if (indio_dev->name)
 		indio_dev->chan_attr_group.attrs[attrn++] = &dev_attr_name.attr;
+	if (clk)
+		indio_dev->chan_attr_group.attrs[attrn++] = clk;
 
 	indio_dev->groups[indio_dev->groupcounter++] =
 		&indio_dev->chan_attr_group;