Re: [PATCH] iio: hid-sensor-trigger: Fix sometimes not powering up the sensor after resume

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Sun, 2018-04-15 at 15:58 +0100, Jonathan Cameron wrote:
> On Sat, 14 Apr 2018 17:09:09 +0200
> Hans de Goede <hdegoede@redhat.com> wrote:
> 
> > hid_sensor_set_power_work() powers the sensors back up after a
> > resume
> > based on the user_requested_state atomic_t.
> > 
> > But hid_sensor_power_state() treats this as a boolean flag, leading
> > to
> > the following problematic scenario:
> > 
> > 1) Some app starts using the iio-sensor in buffered / triggered
> > mode,
> >    hid_sensor_data_rdy_trigger_set_state(true) gets called, setting
> >    user_requested_state to 1.
> > 2) Something directly accesses a _raw value through sysfs, leading
> >    to a call to hid_sensor_power_state(true) followed by
> >    hid_sensor_power_state(false) call, this sets
> > user_requested_state
> >    to 1 followed by setting it to 0.
> > 3) Suspend/resume the machine, hid_sensor_set_power_work() now does
> >    NOT power the sensor back up because user_requested_state
> > (wrongly)
> >    is 0. Which stops the app using the sensor in buffered mode from
> >    receiving any new values.
> > 
> > This commit changes user_requested_state to a counter tracking how
> > many
> > times hid_sensor_power_state(true) was called instead, fixing this.
> > 
> > Cc: Bastien Nocera <hadess@hadess.net>
> > Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> > Signed-off-by: Hans de Goede <hdegoede@redhat.com>

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

Which App is doing like this?

Thanks,
Srinivas


> 
> Looks sensible to me.
> 
> I'll give it a few days at least though for others to comment.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  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 cfb6588565ba..4905a997a7ec 100644
> > --- a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
> > +++ b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
> > @@ -178,14 +178,14 @@ int hid_sensor_power_state(struct
> > hid_sensor_common *st, bool state)
> >  #ifdef CONFIG_PM
> >  	int ret;
> >  
> > -	atomic_set(&st->user_requested_state, state);
> > -
> >  	if (atomic_add_unless(&st->runtime_pm_enable, 1, 1))
> >  		pm_runtime_enable(&st->pdev->dev);
> >  
> > -	if (state)
> > +	if (state) {
> > +		atomic_inc(&st->user_requested_state);
> >  		ret = pm_runtime_get_sync(&st->pdev->dev);
> > -	else {
> > +	} else {
> > +		atomic_dec(&st->user_requested_state);
> >  		pm_runtime_mark_last_busy(&st->pdev->dev);
> >  		pm_runtime_use_autosuspend(&st->pdev->dev);
> >  		ret = pm_runtime_put_autosuspend(&st->pdev->dev);
> 
>