From: Alan Stern <stern@rowland.harvard.edu>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ulf Hansson <ulf.hansson@linaro.org>,
Kevin Hilman <khilman@linaro.org>,
Russell King <rmk+kernel@arm.linux.org.uk>,
Krzysztof Kozlowski <k.kozlowski@samsung.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/2] PM / Runtime: Add pm_runtime_enable_recursive
Date: Sat, 4 Jul 2015 10:37:55 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1507041021080.19175-100000@netrider.rowland.org> (raw)
In-Reply-To: <1564143.gqjAhPtVFo@vostro.rjw.lan>
On Sat, 4 Jul 2015, Rafael J. Wysocki wrote:
> > >> > Perhaps the pm_runtime_suspended_if_enabled() test should be changed to
> > >> > pm_runtime_status_suspended(). Then it won't matter whether the
> > >> > descendant devices are enabled for runtime PM.
> > >>
> > >> Yeah, that would remove the need for messing with the runtime PM
> > >> enable status of descendant devices, but I wonder why Rafael went that
> > >> way initially.
> > >
> > > I forget the details. Probably it was just to be safe. We probably
> > > thought that if a device was disabled for runtime PM then its runtime
> > > PM status might not be accurate. But if direct_complete is set then it
> > > may be reasonable to assume that the runtime PM status _is_ accurate.
> >
> > Cool.
>
> We're walking a grey area here. What exactly does power.direct_complete mean
> for devices whose runtime PM is disabled?
> > Let's see what Rafael thinks about these two issues. It seems to me
> > that the hardest part is dealing with drivers/subsystems that have no
> > runtime PM support. In such cases, we have to be very careful not to
> > use direct_complete unless we know that the device does no power
> > management at all.
>
> Precisely.
All right, we can make a decision and document it. The following seems
reasonable to me:
If dev->power.direct_complete is set then the PM core will
assume that dev->power.rpm_status is accurate even when
dev->power.disable_depth > 0. The core will obey the
.direct_complete setting regardless of .disable_depth.
As a consequence, devices that support system sleep but don't
support runtime PM must _never_ have .direct_complete set.
On the other hand, if a device (such as a "virtual" device)
requires no callbacks for either system sleep or runtime PM,
then there is no harm in setting .direct_complete. Indeed,
doing so may help speed up an ancestor device's sleep
transition.
How does that sound?
Alan Stern
next prev parent reply other threads:[~2015-07-05 9:24 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-19 14:11 [PATCH v3 0/2] PM: direct_complete_default and pm_runtime_enable_recursive Tomeu Vizoso
2015-05-19 14:11 ` [PATCH v3 1/2] PM / sleep: Add power.direct_complete_default flag Tomeu Vizoso
2015-05-19 17:50 ` Alan Stern
2015-05-19 20:47 ` Ulf Hansson
2015-05-19 23:38 ` Rafael J. Wysocki
2015-05-19 14:11 ` [PATCH v3 2/2] PM / Runtime: Add pm_runtime_enable_recursive Tomeu Vizoso
2015-05-19 17:49 ` Alan Stern
2015-05-19 23:39 ` Rafael J. Wysocki
2015-05-20 9:03 ` Tomeu Vizoso
2015-05-20 14:24 ` Alan Stern
2015-07-02 13:59 ` Tomeu Vizoso
2015-07-02 15:21 ` Alan Stern
2015-07-03 8:11 ` Tomeu Vizoso
2015-07-03 14:16 ` Alan Stern
2015-07-03 14:22 ` Tomeu Vizoso
2015-07-03 15:11 ` Alan Stern
2015-07-04 0:32 ` Rafael J. Wysocki
2015-07-04 0:31 ` Rafael J. Wysocki
2015-07-04 14:37 ` Alan Stern [this message]
2015-07-05 23:36 ` Rafael J. Wysocki
2015-07-07 0:07 ` Rafael J. Wysocki
2015-07-07 14:55 ` Alan Stern
2015-07-07 22:06 ` Rafael J. Wysocki
2015-07-08 20:31 ` Alan Stern
2015-07-14 13:19 ` Tomeu Vizoso
2015-07-14 21:57 ` Alan Stern
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.44L0.1507041021080.19175-100000@netrider.rowland.org \
--to=stern@rowland.harvard.edu \
--cc=dmitry.torokhov@gmail.com \
--cc=gregkh@linuxfoundation.org \
--cc=k.kozlowski@samsung.com \
--cc=khilman@linaro.org \
--cc=laurent.pinchart@ideasonboard.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=pavel@ucw.cz \
--cc=rjw@rjwysocki.net \
--cc=rmk+kernel@arm.linux.org.uk \
--cc=tomeu.vizoso@collabora.com \
--cc=ulf.hansson@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).