linux-kernel - Re: [PATCH v2] PM / sleep: add configurable delay for pm

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Message-ID: <20150222122754.GA7955@amd>
Date:	Sun, 22 Feb 2015 13:27:54 +0100
From:	Pavel Machek <pavel@....cz>
To:	Brian Norris <computersforpeace@...il.com>
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>,
	Florian Fainelli <f.fainelli@...il.com>,
	Kevin Cernekee <cernekee@...il.com>,
	Chirantan Ekbote <chirantan@...omium.org>
Subject: Re: [PATCH v2] PM / sleep: add configurable delay for pm_test

On Sun 2015-02-22 00:26:54, Brian Norris 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.
> 
> This patch turns this 5 second delay into a configurable module
> parameter, so users can determine how long to wait in this
> pseudo-suspend state before resuming the system.
> 
> Example (wait 30 seconds);
> 
>   # echo 30 > /sys/module/suspend/parameters/pm_test_delay
>   # echo core > /sys/power/pm_test
>   # time echo mem  > /sys/power/state
>   ...
>   [   17.583625] suspend debug: Waiting for 30 second(s).
>   ...
>   real	0m30.381s
>   user	0m0.017s
>   sys	0m0.080s
> 
> Signed-off-by: Brian Norris <computersforpeace@...il.com>

Acked-by: Pavel Machek <pavel@....cz>

(Does this need documentation in kernel-parameters.txt or in place
where pm_test is documented?)

Thanks,
								Pavel
								

-- 
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