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. > > The new rules for making the idleness decision are simple: > > 1. system may suspend if and only if no suspend blockers are held > > 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 _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
