linux-kernel - Re: [PATCH] PM / sleep: add configurable delay for pm

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Date:	Thu, 4 Sep 2014 10:54:50 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki\"" <rjw@...ysocki.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH] PM / sleep: add configurable delay for pm_test

On Thu, Sep 04, 2014 at 09:14:12AM +0200, Pavel Machek wrote:
> > When CONFIG_PM_DEBUG=y, we provide a sysfs file (/sys/power/pm_test) for
> > selecting one of a few suspend test modes, where rather than entering a
> > full suspend state, the kernel will perform some subset of suspend
> > steps, wait 5 seconds, and then resume back to normal operation.
> > 
> > This mode is useful for (among other things) observing the state of the
> > system just before entering a sleep mode, for debugging or analysis
> > purposes. However, a constant 5 second wait is not sufficient for some
> > sorts of analysis; for example, on an SoC, one might want to use
> > external tools to probe the power states of various on-chip controllers
> > or clocks.
> 
> When you are doing this kind of analysis, perhaps directly modifying
> kernel source is the way to go ...?

That's what I've been doing for now, but I have a few engineers who need
to do this sort of testing and aren't kernel developers. I could
continue to maintain my own patch for this, but I just thought I'd see
what others thought.

Is there a good reason this can't be in mainline? These features are
hidden behind a Kconfig symbol called PM_DEBUG anyway, and I think this
classifies as a pretty simple extension to the limited existing PM
debugging options.

Regards,
Brian
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