On 22 October 2015 at 02:54, Rafael J. Wysocki [off-list ref] wrote:

On Tuesday, October 20, 2015 06:21:55 PM Tomeu Vizoso wrote:

quoted

On 20 October 2015 at 18:04, Alan Stern [off-list ref] wrote:

quoted

On Tue, 20 Oct 2015, Mark Brown wrote:

quoted

On Tue, Oct 20, 2015 at 10:40:03AM -0400, Alan Stern wrote:

quoted

Furthermore, that applies only to devices that use synchronous suspend.
Async suspend is becoming common, and there the only restrictions are
parent-child relations plus whatever explicit requirements that drivers
impose by calling device_pm_wait_for_dev().

Hrm, this is the first I'd noticed that feature though I see the initial
commit dates from January.

Async suspend and device_pm_wait_for_dev() were added in January 2010,
not 2015!

quoted

 It looks like most of the users are PCs at
the minute but we should be using it more widely for embedded things,
there's definitely some cases I'm aware of where it will allow us to
remove some open coding.

It does seem like we want to be feeding dependency information we
discover for probing way into the suspend dependencies...

Rafael has been thinking about a way to do this systematically.
Nothing concrete has emerged yet.

This iteration of the series would make this quite easy, as
dependencies are calculated before probes are attempted:

https://lkml.org/lkml/2015/6/17/311

Well, if you know how to represent "links" between devices, the mechanism
introduced here doesn't really add much value, because in that case the
core knows what the dependencies are in the first place and can only
defer the probes that have to be deferred.

By "here" you mean what you are proposing for ordering device
suspends, or on-demand probing?

If you meant that probing on-demand is unneeded if we already have
dependency information, I agree with you and that's why I only pushed
forward on-demand, as the approach linked above introduced some
duplication when inferring the dependencies. Maybe that could be
avoided without too much refactoring.

In any case, Thierry mentioned the other day in #tegra that one could
also collect dependency information as a follow up to the on-demand
series by calling device_depend() or such instead of
of_device_probe().

Regards,

Tomeu

Thanks,
Rafael

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/