Re: [PATCH] gpio: omap-gpio: add support for pm_runtime autosuspend

[Kevin Hilman <khilman@deeprootsystems.com>]

Santosh Shilimkar <santosh.shilimkar@ti.com> writes:

[...]

> Just to summaries, there are 3 things we are talking here.

Santosh, thanks for the summary.  You are right on.

> 1. Delaying the idle with a timeout which $subject patch is
> trying to do to reduce latency for interrupts. That itself
> is reasonable.

I agree, this is reasonable.   IMO, adding autosuspend should be done as
an isolated patch and kept separate from any other cleanup or changes.

Also, as Jon mentioned, I think this should be done with a default
timeout of zero so that current behaviour is unchanged.  Tim can then
set the timeout from userspace for his usecase and everyone is happy.

> 2. Removal of the bank "mod_usage" which is also clubbed
> in $subject path. Ofcourse that break the current driver
> for idle. So that change needs to be made with better thought
> and in a separate patch. This is doable.

I had this discussion with Charu/Tarun during the last round of cleanup
because I didn't like this mod_usage either.  The alternative is to do a
'get' for every GPIO in the bank since runtime PM is doing the
usecounting already.  As Santosh said, this is fine for suspend, but for
idle it means calling 'put' for every enabled GPIO in the bank instead
of just forcing things with a single 'put.'

> 3. Removing omap_gpio_[prepare/resume]_for_idle() with soome thing
> better. For this one though, so far I have not come across a good
> solution. Ideas/Solution is welcome !!

I agree that the prepare/resume idle hooks a are ugly and should be
removed, but this needs quite a bit more thought.  In particular,
the 'remove triggering' stuff that is done needs pretty close
examination.

I'm not saying it can't be done, but patches to do this should be
separate, well described and well tested, especially with off-mode.

Kevin