patch "iio: hid-sensor-trigger: Fix the race with user space powering up" added to staging-linus

patch "iio: hid-sensor-trigger: Fix the race with user space powering up" added to staging-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    iio: hid-sensor-trigger: Fix the race with user space powering up

to my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From f1664eaacec31035450132c46ed2915fd2b2049a Mon Sep 17 00:00:00 2001
From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Date: Sat, 12 Aug 2017 09:09:21 -0700
Subject: iio: hid-sensor-trigger: Fix the race with user space powering up
 sensors

It has been reported for a while that with iio-sensor-proxy service the
rotation only works after one suspend/resume cycle. This required a wait
in the systemd unit file to avoid race. I found a Yoga 900 where I could
reproduce this.

The problem scenerio is:
- During sensor driver init, enable run time PM and also set a
  auto-suspend for 3 seconds.
	This result in one runtime resume. But there is a check to avoid
a powerup in this sequence, but rpm is active
- User space iio-sensor-proxy tries to power up the sensor. Since rpm is
  active it will simply return. But sensors were not actually
powered up in the prior sequence, so actaully the sensors will not work
- After 3 seconds the auto suspend kicks

If we add a wait in systemd service file to fire iio-sensor-proxy after
3 seconds, then now everything will work as the runtime resume will
actually powerup the sensor as this is a user request.

To avoid this:
- Remove the check to match user requested state, this will cause a
  brief powerup, but if the iio-sensor-proxy starts immediately it will
still work as the sensors are ON.
- Also move the autosuspend delay to place when user requested turn off
  of sensors, like after user finished raw read or buffer disable

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Tested-by: Bastien Nocera <hadess@hadess.net>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/common/hid-sensors/hid-sensor-trigger.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
index 16ade0a0327b..0e4b379ada45 100644
--- a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
+++ b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
@@ -111,8 +111,6 @@ static int _hid_sensor_power_state(struct hid_sensor_common *st, bool state)
 	s32 poll_value = 0;
 
 	if (state) {
-		if (!atomic_read(&st->user_requested_state))
-			return 0;
 		if (sensor_hub_device_open(st->hsdev))
 			return -EIO;
 
@@ -161,6 +159,9 @@ static int _hid_sensor_power_state(struct hid_sensor_common *st, bool state)
 				       &report_val);
 	}
 
+	pr_debug("HID_SENSOR %s set power_state %d report_state %d\n",
+		 st->pdev->name, state_val, report_val);
+
 	sensor_hub_get_feature(st->hsdev, st->power_state.report_id,
 			       st->power_state.index,
 			       sizeof(state_val), &state_val);
@@ -182,6 +183,7 @@ int hid_sensor_power_state(struct hid_sensor_common *st, bool state)
 		ret = pm_runtime_get_sync(&st->pdev->dev);
 	else {
 		pm_runtime_mark_last_busy(&st->pdev->dev);
+		pm_runtime_use_autosuspend(&st->pdev->dev);
 		ret = pm_runtime_put_autosuspend(&st->pdev->dev);
 	}
 	if (ret < 0) {
@@ -285,8 +287,6 @@ int hid_sensor_setup_trigger(struct iio_dev *indio_dev, const char *name,
 	/* Default to 3 seconds, but can be changed from sysfs */
 	pm_runtime_set_autosuspend_delay(&attrb->pdev->dev,
 					 3000);
-	pm_runtime_use_autosuspend(&attrb->pdev->dev);
-
 	return ret;
 error_unreg_trigger:
 	iio_trigger_unregister(trig);
-- 
2.14.1