iio: hid-sensor-hub: Implement batch mode

HID sensor hubs using Integrated Senor Hub (ISH) has added capability to
support batch mode. This allows host processor to go to sleep for extended
duration, while the sensor hub is storing samples in its internal buffers.

'Commit f4f4673b7535 ("iio: add support for hardware fifo")' implements
feature in IIO core to implement such feature. This feature is used in
bmc150-accel-core.c to implement batch mode. This implementation allows
software device buffer watermark to be used as a hint to adjust hardware
FIFO.

But HID sensor hubs don't allow to change internal buffer size of FIFOs.
Instead an additional usage id to set "maximum report latency" is defined.
This allows host to go to sleep upto this latency period without getting
any report. Since there is no ABI to set this latency, a new attribute
"hwfifo_timeout" is added so that user mode can specify a latency.

This change checks presence of usage id to get/set maximum report latency
and if present, it will expose hwfifo_timeout.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

2 files changed, 124 insertions, 0 deletions

diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
index 0e05f6d1e761..f5d4d786e193 100644
--- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
+++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
@@ -410,6 +410,48 @@ int hid_sensor_get_reporting_interval(struct hid_sensor_hub_device *hsdev,
 
 }
 
+static void hid_sensor_get_report_latency_info(struct hid_sensor_hub_device *hsdev,
+					       u32 usage_id,
+					       struct hid_sensor_common *st)
+{
+	sensor_hub_input_get_attribute_info(hsdev, HID_FEATURE_REPORT,
+					    usage_id,
+					    HID_USAGE_SENSOR_PROP_REPORT_LATENCY,
+					    &st->report_latency);
+
+	hid_dbg(hsdev->hdev, "Report latency attributes: %x:%x\n",
+		st->report_latency.index, st->report_latency.report_id);
+}
+
+int hid_sensor_get_report_latency(struct hid_sensor_common *st)
+{
+	int ret;
+	int value;
+
+	ret = sensor_hub_get_feature(st->hsdev, st->report_latency.report_id,
+				     st->report_latency.index, sizeof(value),
+				     &value);
+	if (ret < 0)
+		return ret;
+
+	return value;
+}
+EXPORT_SYMBOL(hid_sensor_get_report_latency);
+
+int hid_sensor_set_report_latency(struct hid_sensor_common *st, int latency_ms)
+{
+	return sensor_hub_set_feature(st->hsdev, st->report_latency.report_id,
+				      st->report_latency.index,
+				      sizeof(latency_ms), &latency_ms);
+}
+EXPORT_SYMBOL(hid_sensor_set_report_latency);
+
+bool hid_sensor_batch_mode_supported(struct hid_sensor_common *st)
+{
+	return st->report_latency.index > 0 && st->report_latency.report_id > 0;
+}
+EXPORT_SYMBOL(hid_sensor_batch_mode_supported);
+
 int hid_sensor_parse_common_attributes(struct hid_sensor_hub_device *hsdev,
 					u32 usage_id,
 					struct hid_sensor_common *st)
@@ -451,6 +493,8 @@ int hid_sensor_parse_common_attributes(struct hid_sensor_hub_device *hsdev,
 	} else
 		st->timestamp_ns_scale = 1000000000;
 
+	hid_sensor_get_report_latency_info(hsdev, usage_id, st);
+
 	hid_dbg(hsdev->hdev, "common attributes: %x:%x, %x:%x, %x:%x %x:%x %x:%x\n",
 		st->poll.index, st->poll.report_id,
 		st->report_state.index, st->report_state.report_id,
diff --git a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
index 0b5dea050239..16ade0a0327b 100644
--- a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
+++ b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
@@ -26,9 +26,84 @@
 #include <linux/hid-sensor-hub.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/trigger.h>
+#include <linux/iio/buffer.h>
 #include <linux/iio/sysfs.h>
 #include "hid-sensor-trigger.h"
 
+static ssize_t _hid_sensor_set_report_latency(struct device *dev,
+					      struct device_attribute *attr,
+					      const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct hid_sensor_common *attrb = iio_device_get_drvdata(indio_dev);
+	int integer, fract, ret;
+	int latency;
+
+	ret = iio_str_to_fixpoint(buf, 100000, &integer, &fract);
+	if (ret)
+		return ret;
+
+	latency = integer * 1000 + fract / 1000;
+	ret = hid_sensor_set_report_latency(attrb, latency);
+	if (ret < 0)
+		return len;
+
+	attrb->latency_ms = hid_sensor_get_report_latency(attrb);
+
+	return len;
+}
+
+static ssize_t _hid_sensor_get_report_latency(struct device *dev,
+					      struct device_attribute *attr,
+					      char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct hid_sensor_common *attrb = iio_device_get_drvdata(indio_dev);
+	int latency;
+
+	latency = hid_sensor_get_report_latency(attrb);
+	if (latency < 0)
+		return latency;
+
+	return sprintf(buf, "%d.%06u\n", latency / 1000, (latency % 1000) * 1000);
+}
+
+static ssize_t _hid_sensor_get_fifo_state(struct device *dev,
+					  struct device_attribute *attr,
+					  char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct hid_sensor_common *attrb = iio_device_get_drvdata(indio_dev);
+	int latency;
+
+	latency = hid_sensor_get_report_latency(attrb);
+	if (latency < 0)
+		return latency;
+
+	return sprintf(buf, "%d\n", !!latency);
+}
+
+static IIO_DEVICE_ATTR(hwfifo_timeout, 0644,
+		       _hid_sensor_get_report_latency,
+		       _hid_sensor_set_report_latency, 0);
+static IIO_DEVICE_ATTR(hwfifo_enabled, 0444,
+		       _hid_sensor_get_fifo_state, NULL, 0);
+
+static const struct attribute *hid_sensor_fifo_attributes[] = {
+	&iio_dev_attr_hwfifo_timeout.dev_attr.attr,
+	&iio_dev_attr_hwfifo_enabled.dev_attr.attr,
+	NULL,
+};
+
+static void hid_sensor_setup_batch_mode(struct iio_dev *indio_dev,
+					struct hid_sensor_common *st)
+{
+	if (!hid_sensor_batch_mode_supported(st))
+		return;
+
+	iio_buffer_set_attrs(indio_dev->buffer, hid_sensor_fifo_attributes);
+}
+
 static int _hid_sensor_power_state(struct hid_sensor_common *st, bool state)
 {
 	int state_val;
@@ -141,6 +216,9 @@ static void hid_sensor_set_power_work(struct work_struct *work)
 				       sizeof(attrb->raw_hystersis),
 				       &attrb->raw_hystersis);
 
+	if (attrb->latency_ms > 0)
+		hid_sensor_set_report_latency(attrb, attrb->latency_ms);
+
 	_hid_sensor_power_state(attrb, true);
 }
 
@@ -192,6 +270,8 @@ int hid_sensor_setup_trigger(struct iio_dev *indio_dev, const char *name,
 	attrb->trigger = trig;
 	indio_dev->trig = iio_trigger_get(trig);
 
+	hid_sensor_setup_batch_mode(indio_dev, attrb);
+
 	ret = pm_runtime_set_active(&indio_dev->dev);
 	if (ret)
 		goto error_unreg_trigger;