Re: [PATCH] iio: hid-sensor-trigger: Fix the race with user space powering up sensors

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 12 Aug 2017 09:09:21 -0700
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> wrote:

> 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>
> 
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan
> ---
> Changes:
> Removed RFT and added Tested-by tag.
> 
>  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 16ade0a..0e4b379 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);