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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 16-04-18 00:34, Srinivas Pandruvada wrote:
> 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?

No app, just something I noticed while manually testing the
accelerometer while iio-sensor-proxy was also active.

Regards,

Hans



> 
> 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);
>>
>>