lkml.org 
[lkml]   [2010]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 0/8] Suspend block api (version 6)
    * Rafael J. Wysocki <rjw@sisk.pl> [100510 13:27]:
    > On Monday 10 May 2010, Kevin Hilman wrote:
    > > Hello,
    >
    > Hi Kevin,
    >
    > > I think many folks are still confused about exactly the problem being
    > > solved by this series as well as mixed up between opportunistic
    > > suspend and suspend blockers. Also, how this series impatcs the rest
    > > of the kernel (especially PM-aware drivers and subsystems) has caused
    > > a bit of confusion.
    > >
    > > To help with the confusion, I think a much clearer description of the
    > > problem being solved and the proposed solution is needed.
    > >
    > > To that end, I created a starting point for that below which
    > > summarizes how I understand the problem and the proposed solution, but
    > > of course this should be filled out in more detail and updated as part
    > > of the documentation that goes with this series.
    > >
    > > Hope this helps improve the understanding of this feature,
    >
    > Yes, I think this is helpful.
    >
    > > Table of Contents
    > > =================
    > > 1 Problem Statement
    > > 2 Solution: Opportunistic suspend
    > > 2.1 When to use a suspend blocker
    > > 2.2 Usage in PM aware drivers
    > >
    > >
    > > 1 Problem Statement
    > > ~~~~~~~~~~~~~~~~~~~~
    > >
    > > Want to to hit deep power state, even when the system is not actually
    > > idle.
    > >
    > > Why?
    > >
    > > - some hardware is not capable of deep power states in idle
    > > - difficulty getting userspace and/or kernel to be idle
    > >
    > > 2 Solution: Opportunistic suspend
    > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > >
    > > Create an additional "idle path" which has new rules for determining
    > > idleness. When this new "idle" is reached, trigger full-system
    > > suspend. Since a suspend is triggered whenever the opportunity
    > > arises, this is called opportunistic suspend.

    I agree, this is is the right way to handle when to enter suspend.

    Especially if the system needs to run while waiting for something
    to happen before being able to suspend.

    > > The new rules for making the idleness decision are simple:
    > >
    > > 1. system may suspend if and only if no suspend blockers are held

    To me it sounds like this should only be allowed to happen when you do:

    # echo 1 > /sys/power/suspend_while_idle

    As it kills the timers and leads to non-standard behaviour of the apps
    as they won't run :)

    And then the remaining question is how to make sure the use cases
    below can be handled in a clean way.

    > > 2.1 When to use a suspend blocker
    > > ==================================
    > >
    > > [A list of reasons why suspend blockers might be used would be very
    > > helpful here.]
    > >
    > > - ensure wakeup events propagate to userspace (e.g. keypad example in doc)
    > >
    > > - screen is on
    > >
    > > - someone mentioned "Google use cases"
    > > (would be nice to hear about more of these)
    >
    > Yes, I think the Android developers know quite a few cases where suspend
    > blockers are useful.
    >
    > > 2.2 Usage in PM aware drivers
    > > ==============================
    > >
    > > [An example of how a driver already using runtime PM would use
    > > a suspend blocker would also be helpful.
    >
    > When we have any drivers using both in the tree, they will be used as examples
    > here.
    >
    > Thanks,
    > Rafael
    > --
    > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html
    > Please read the FAQ at http://www.tux.org/lkml/


    \
     
     \ /
      Last update: 2010-05-12 10:15    [W:0.033 / U:153.224 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site