Re: [PATCH v2] HID: i2c-hid: Fix suspend/resume when already runtime suspended

Doug Anderson
2015-03-10T16:15:28Z

Mika,

On Tue, Mar 10, 2015 at 5:23 AM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> On Mon, Mar 09, 2015 at 12:44:47PM -0700, Doug Anderson wrote:
>> If the i2c-hid device was runtime suspended and then the system
>> suspended itself we'd end up disabling interrupts twice (in
>> i2c_hid_runtime_suspend and i2c_hid_suspend) and not reenabling them
>> until later when the i2c-hid device was runtime resumed.
>> Unfortunately the i2c_hid_resume() calls i2c_hid_hwreset() and that
>> only works properly if interrupts are enabled.
>>
>> We can fix this by taking the advice from "runtime_pm.txt".
>> Specifically we'll change i2c-hid to always resume to full power.
>> This only works if our parents are also resumed to full power, but
>> given the suggestion in "runtime_pm.txt" this seems a reasonable
>> assumption.
>>
>> Signed-off-by: Doug Anderson <dianders@chromium.org>
>> ---
>> Note that this was tested on a 3.14 kernel with backports. Any
>> testing that folks can do on ToT is appreciated.
>>
>> Changes in v2:
>> - Move pm_runtime_enable() higher in resume
>
> Hmm, I tried on one machine with Atmel touch panel. I modified i2c-hid.c
> a bit to print out when it is running suspend/resume hooks. Here is what
> I got:
>
> [ 7.506455] i2c_hid i2c-ATML1000:00: PM: i2c-hid runtime suspend
>
> This is the initialization and after that the device is runtime
> suspended.
>
> Now I put the machine to system sleep (using echo mem >
> /sys/power/state):
>
> [ 26.988867] i2c_hid i2c-ATML1000:00: PM: i2c-hid runtime resume

Thanks for testing! Can you do a "dump_stack()" here? I'm curious
why it's deciding to runtime resume. Maybe something changed between
3.14 and ToT?

> [ 27.002957] i2c_hid i2c-ATML1000:00: PM: i2c-hid suspend
>
> So the PM core will kick the device out of runtime suspend before it
> suspends it again.
>
> Pressing power button will resume the device:
>
> [ 28.238934] i2c_hid i2c-ATML1000:00: PM: i2c-hid resume
> [ 29.941579] i2c_hid i2c-ATML1000:00: PM: i2c-hid runtime suspend
>
> and since the device is not being used, it will runtime suspend itself.
>
> In other words, I'm not sure if this patch is needed. It would be good
> if you could do similar testing using mainline kernel (if possible at
> all).

Unfortunately it's not so easy. For my platform suspend/resume is
just barely functional as it is, but then I'm on a board that's
further not supported upstream.

If folks upstream can't reproduce the problems then there's no reason
to take my patch...

-Doug