Re: [PATCH v4 5/7] iio: hid-sensors: use asynchronous resume

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

On Mon, 2016-08-15 at 10:53 -0700, Dmitry Torokhov wrote:
> On Mon, Aug 15, 2016 at 10:29:23AM -0700, Srinivas Pandruvada wrote:
> > 
> > On Mon, 2016-08-15 at 10:14 -0700, Dmitry Torokhov wrote:
> > > 
> > > On Mon, Aug 15, 2016 at 9:42 AM, Srinivas Pandruvada
> > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > 
> > > > 
> > > > On Mon, 2016-08-15 at 08:45 -0700, Dmitry Torokhov wrote:
> > > > > 
> > > > > 
> > > > > On Mon, Aug 15, 2016 at 7:52 AM, Jonathan Cameron <jic23@kern
> > > > > el.o
> > > > > rg>
> > > > > wrote:
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > On 15/08/16 15:07, Jonathan Cameron wrote:
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > On 07/08/16 11:15, Jiri Kosina wrote:
> > > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > On Sun, 7 Aug 2016, Srinivas Pandruvada wrote:
> > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > Some platforms power off sensor hubs during S3
> > > > > > > > > suspend,
> > > > > > > > > which
> > > > > > > > > will require
> > > > > > > > > longer time to resume. This hurts system resume time,
> > > > > > > > > so
> > > > > > > > > resume
> > > > > > > > > asynchronously.
> > > > > > > > > 
> > > > > > > > > Signed-off-by: Srinivas Pandruvada <srinivas.pandruva
> > > > > > > > > da@l
> > > > > > > > > inux
> > > > > > > > > .intel.com>
> > > > > > > > Jonathan, are you going to cherry-pick this patch from
> > > > > > > > the
> > > > > > > > series?
> > > > > > > > Alternatively, if you're okay with it, I can pull it in
> > > > > > > > together with the
> > > > > > > > whole set with your Acked-by or Reviewed-by.
> > > > > > > > 
> > > > > > > I'll take it via IIO. Got a bit of catching up to do
> > > > > > > (been on
> > > > > > > holiday)
> > > > > > Applied to the togreg branch of iio.git - initially pushed
> > > > > > out
> > > > > > as
> > > > > > testing for the autobuilders to play with it.
> > > > > > This one is not really connected to the others so makes
> > > > > > sense
> > > > > > to
> > > > > > take it separately.
> > > > > > 
> > > > > > I'm out of my depth on the rest of the patches in this
> > > > > > series
> > > > > > and don't have time to learn enough to follow them! Sorry I
> > > > > > can't help on that front.
> > > > > About this patch: me sees a new work, me does not see new
> > > > > calls
> > > > > to
> > > > > cancel_work_sync() or flush_work() anywhere, me gets worried.
> > > > This work is scheduled during resume and is not delayed call.
> > > > Only
> > > > time
> > > > really we need to cancel or flush if module is unloaded before
> > > > resume
> > > > work, not sure if this case realistic. Do you see any other
> > > > case
> > > > possible?
> > > Runtime resume can happen at any time, I can unload module or
> > > unbind
> > > it at any time. I also wasn't aware that our implementation goal
> > > for
> > > locking rules/lifetime rules/etc was "realistic" instead of
> > > "correct".
> > This is not for runtime_resume, this is for regular S3 suspend. But
> > I
> > agree, I will submit a patch for correctness.
> Thinking about it some more: if you are off-loading powering up the
> hub
> to work structure it means that the hub is not actually powered up
> when
> the rest of the system thinks it is, which may cause subsequent
> requests
> to it fail.
> 
> You need to make sure noone is actually interacting with the device
> until you are done powering it up.
This will happen as the input request will be waiting till sensor is
powered up and response is received.

Thanks,
Srinivas


> 
> Thanks.
>