linux-kernel - Re: [linux-pm] [patch update 2 fix] PM: Introduce core framework for run-time PM of I/O devices

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Date:	Mon, 22 Jun 2009 10:15:41 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Greg KH <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [linux-pm] [patch update 2 fix] PM: Introduce core framework for run-time PM of I/O devices

Am Montag, 22. Juni 2009 08:20:43 schrieb Magnus Damm:
> I'd like to call pm_request_suspend() from interrupt context. I don't
> depend on it, but being able to perform runtime suspend directly from
> the ISR would be convenient from a device driver POV. I'm not sure if
> that should result in bus/device ->runtime_suspend() calls from
> interrupt context though.
>
> In my case the bus specific code for ->runtime_suspend() may just
> decrease the usage count of the powerdomain but refrain from calling
> the device ->runtime_suspend() callbacks until all devices in the
> powerdomain have been suspended. The bus/device runtime suspend
> callbacks do not need to be executed from interrupt context. Just
> noting that the device is idle is enough at interrupt time. This could
> be handled by generic code IMO.

>From practical experience doing USB power management I can tell
you that requesting suspension from interrupt makes things a lot
easier for driver writers.

	Regards
		Oliver

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