Hi Jonathan,
	I add more information about the patch:
	
Bug found: 
When we cat sensor incli sensor data with hysteresis value is 0, there always have streamed sensor data output,
But when system enter S3 and resume back, the streaming thread is still on but there is not streaming sensor data output.
Test data as below:
279: 2017-01-24 01:16:00.279385 *5* incli_3d: Min Delta: 99.779ms, Max Delta: 100.316ms, Received: 10/s, Overall: 170/16s; Sample values ,0.010546,-0.006712,2.797579
280: 2017-01-24 01:16:41.211385 *5* incli_3d: Min Delta: 100.16ms, Max Delta: 40924.6ms, Received: 2/s, Overall: 172/19s; Sample values ,0.010546,-0.006712,2.797579
281: 2017-01-24 01:16:42.219892 *5* incli_3d: Min Delta: 0.023ms, Max Delta: 543.28ms, Received: 2/s, Overall: 174/20s; Sample values ,0.010546,-0.006712,2.797579
282: 2017-01-24 01:16:42.755548 *4* CIIOSensorInform::sensor_wait_event poll timeout
283: 2017-01-24 01:16:43.223062 *5* incli_3d: Min Delta: --, Max Delta: --, Received: 0/s, Overall: 174/21s
284: 2017-01-24 01:16:43.756980 *4* CIIOSensorInform::sensor_wait_event poll timeout
285: 2017-01-24 01:16:44.225527 *5* incli_3d: Min Delta: --, Max Delta: --, Received: 0/s, Overall: 174/22s
286: 2017-01-24 01:16:44.758467 *4* CIIOSensorInform::sensor_wait_event poll timeout
287: 2017-01-24 01:16:45.228082 *5* incli_3d: Min Delta: --, Max Delta: --, Received: 0/s, Overall: 174/23s
288: 2017-01-24 01:16:45.759958 *4* CIIOSensorInform::sensor_wait_event poll timeout

Root cause: 
when sensor resume back from S3, the sensor property user set is lost.
For example, if we set sensor hysteresis value to be 0, then let system enter S3, when resume back, the hysteresis value will be not 0 but the default value 1.

this is not what we want, resume back from S3 should not lose the properties which is set before S3, just because the property setting sequence lead to this lose.

This is patch is a fix patch and needed for stable.

Thanks a lot!

BR
Song Hongyan


-----Original Message-----
From: Jonathan Cameron [mailto:jic23@kernel.org] 
Sent: Sunday, February 26, 2017 12:52 AM
To: Pandruvada, Srinivas <redacted>; linux-input@vger.kernel.org; Song, Hongyan <redacted>; linux-iio@vger.kernel.org
Cc: jikos@kernel.org
Subject: Re: [PATCH] iio: hid-sensor-trigger: Change get poll value function order to avoid sensor properties losing after resume from S3

On 22/02/17 05:40, Pandruvada, Srinivas wrote:

On Wed, 2017-02-22 at 17:17 +0800, Song Hongyan wrote:

quoted

In function _hid_sensor_power_state(), when
hid_sensor_read_poll_value()
is called, sensor's all properties will be updated by the value from 
sensor hardware/firmware.
In some implementation, sensor hardware/firmware will do a power 
cycle during S3. In this case, after resume, once
hid_sensor_read_poll_value()
is called, sensor's all properties which are kept by driver during S3 
will be changed to default value.
But instead, if a set feature function is called first, sensor 
hardware/firmware will be recovered to the last status. So change the
sensor_hub_set_feature() calling order to behind of set feature 
function to avoid sensor properties lose.

Signed-off-by: Song Hongyan <redacted>

Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

Hi Song,

The patch message, whilst excellent on the technical detail, gives me no sense of urgency on this. Is this a fix we want to have heading for stable ASAP or are we looking at something seen in some developmental hardware for example?
Links to bug reports, or examples of hardware suffering from the issue are always helpful as well.

Also for something like this a 'fixes' tag is very helpful when people are looking to back port it.

Anyhow, I'm going to hold off on taking this one until I have more information. Right now it makes little difference as the next fixes pull request from me will probably not be until next weekend.

Thanks,

Jonathan

quoted

---
 drivers/iio/common/hid-sensors/hid-sensor-trigger.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c

b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
index a3cce3a..ecf592d 100644

--- a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
+++ b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c

@@ -51,8 +51,6 @@ static int _hid_sensor_power_state(struct 

hid_sensor_common *st, bool state)
 			st->report_state.report_id,
 			st->report_state.index,
 			HID_USAGE_SENSOR_PROP_REPORTING_STATE_ALL_EV
ENTS_ENUM);
-
-		poll_value = hid_sensor_read_poll_value(st);
 	} else {
 		int val;
 

@@ -89,7 +87,9 @@ static int _hid_sensor_power_state(struct 

hid_sensor_common *st, bool state)
 	sensor_hub_get_feature(st->hsdev, st->power_state.report_id,
 			       st->power_state.index,
 			       sizeof(state_val), &state_val);
-	if (state && poll_value)
+	if (state)
+		poll_value = hid_sensor_read_poll_value(st);
+	if (poll_value > 0)
 		msleep_interruptible(poll_value * 2);
 
 	return 
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quoted

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