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Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend

From Alan Stern <stern@rowland.harvard.edu>
Newsgroups linux.kernel
Subject Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend
Date 2015-09-22 17:30 +0200
Message-ID <qbxG3-P2-35@gated-at.bofh.it> (permalink)
References <qbwTF-86z-55@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Tue, 22 Sep 2015, Oliver Neukum wrote:

> > I'm not sure I understand what you're saying.  Are you suggesting that
> > this "inhibit" mechanism should involve a new callback different from
> 
> Yes, there is no necessary relation to power management. If you put
> your phone into your pocket, you will want to inhibit the touchscreen
> even if that doesn't save power.
> 
> > the existing runtime-PM callbacks?  And when this new callback is
> > invoked, drivers should cancel existing input requests (these devices
> > are input-only) and go to low power?
> 
> Cancel, yes, going to low power is a consequence which needn't bother
> the power subsystem.

Going to low power needn't involve the power subsystem?  That sounds 
weird.

>  You need a callback. If there are spurious
> events, the current heuristics will keep devices awake.
> You must discard them anyway, as they are spurious. There's no point
> in transporting over the bus at all. We can cease IO for input.
> 
> > This would create a parallel runtime-PM mechanism which is independent
> > of the existing one.  Is that really a good idea?
> 
> It isn't strictly PM. It helps PM to do a better job, but
> conceptually it is independent.

So my next question is: _How_ can this help PM to do a better job?  
That is, what are the mechanisms?

One you have already stated: Lack of spurious events will help prevent 
unwanted wakeups (or unwanted failures to go to sleep).

But Dmitry made a stronger claim: Inhibiting an input device should 
allow the device to go to low power.  I would like to know how we can 
implement this cleanly.  The most straightforward approach is to use 
runtime PM, but it's not obvious how this can be made to work with the 
current API.

Alan Stern

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[RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend Irina Tirdea <irina.tirdea@intel.com> - 2015-09-07 22:50 +0200
  Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-07 23:00 +0200
    RE: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend "Tirdea, Irina" <irina.tirdea@intel.com> - 2015-09-08 03:20 +0200
      Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.com> - 2015-09-08 09:40 +0200
        Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-08 23:00 +0200
          Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Ulf Hansson <ulf.hansson@linaro.org> - 2015-09-09 00:30 +0200
            Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-09 02:00 +0200
              Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Octavian Purdila <octavian.purdila@intel.com> - 2015-09-09 13:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-09 14:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.com> - 2015-09-09 16:00 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Octavian Purdila <octavian.purdila@intel.com> - 2015-09-09 17:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-09 22:00 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.com> - 2015-09-10 11:50 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Pavel Machek <pavel@ucw.cz> - 2015-09-21 14:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-09 17:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-09 22:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Colin Cross <ccross@google.com> - 2015-09-09 22:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Pavel Machek <pavel@ucw.cz> - 2015-09-21 14:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-21 16:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-09-21 18:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-21 18:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-09-21 19:00 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-21 19:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-09-21 20:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-21 22:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-09-21 23:00 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.com> - 2015-09-22 14:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-22 16:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.de> - 2015-09-22 16:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-22 17:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.de> - 2015-09-23 05:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Octavian Purdila <octavian.purdila@intel.com> - 2015-09-23 09:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-23 17:00 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-25 02:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-25 16:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-25 21:50 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-25 23:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-25 23:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-26 00:40 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-26 17:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-27 15:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-27 16:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-28 15:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-28 16:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-28 22:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-28 22:30 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Pavel Machek <pavel@ucw.cz> - 2015-10-04 17:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Pavel Machek <pavel@ucw.cz> - 2015-09-27 19:10 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-28 15:20 +0200
                Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Pavel Machek <pavel@ucw.cz> - 2015-09-21 22:30 +0200
      RE: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-08 16:50 +0200
        Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-08 16:50 +0200
          Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-08 17:10 +0200
            Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-08 22:30 +0200
              Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-09 17:30 +0200
        Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Oliver Neukum <oneukum@suse.com> - 2015-09-09 08:30 +0200
          Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing  runtime suspend Alan Stern <stern@rowland.harvard.edu> - 2015-09-09 16:40 +0200

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