On Wed, 02 Jun 2010 15:41:11 -0500 James Bottomley <[email protected]> wrote:
> On Wed, 2010-06-02 at 21:47 +0200, Florian Mickler wrote: > > On Wed, 02 Jun 2010 10:05:11 -0500 > > James Bottomley <[email protected]> wrote: > > > > > On Tue, 2010-06-01 at 21:41 -0700, Arve Hjønnevåg wrote: > > > > No, they have to be two separate constraints, otherwise a constraint > > > > to block suspend would override a constraint to block a low power idle > > > > mode or the other way around. > > > > > > Depends. If you block the system from going into low power idle, does > > > that mean you still want it to be fully suspended? > > > > > > If yes, then we do have independent constraints. If not, they have a > > > hierarchy: > > > > > > * Fully Interactive (no low power idle or suspend) > > > * Partially Interactive (may go into low power idle but not > > > suspend) > > > * None (may go into low power idle or suspend) > > > > > > Which is expressable as a ternary constraint. > > > > > > James > > > > > > > But unblocking suspend at the moment is independent to getting idle. > > If you have the requirement to stay in the highest-idle level (i.e. > > best latency you can get) that does not (currently) mean, that you can > > not suspend. > > I don't understand that as a reason. If we looks at this a qos > constraints, you're saying that the system may not drop into certain low > power states because it might turn something off that's currently being > used by a driver or a process. Suspend is certainly the lowest state of > that because it turns everything off, why would it be legal to drop into > that? > > I also couldn't find this notion of separation of idleness power from > suspend blocking in the original suspend block patch set ... if you can > either tell me where it is, or give me an example of the separated use > cases, I'd understand better. > > > To preserve that explicit fall-through while still having working > > run-time-powermanagement I think the qos-constraints need to be > > separated. > > OK, as above, why? or better yet, just give an example. Hm. Maybe it is me who doesn't understand. With proposed patchset: 1. As soon as we unblock suspend we go down. (i.e. suspending) 2. While suspend is blocked, the idle-loop does it's things. (i.e. runtime power managment -> can give same power-result as suspend) possible cases: 1: - qos-latency-constraints: 1ms, [here: forbids anything other than C1 idle state.] - suspend is blocked 2: - qos latency-constraints: as in 1 - suspend unblocked 3: - qos latency-constraints: infinity, cpu in lowest power state. - suspend is blocked 4: - qos latency-constraints: infinity, cpu in lowest power state. - suspend unblocked in case 2 and 4 we would suspend, regardeless of the qos-latency. in case 1 and 3 we would stay awake, regardeless of the qos-latency constraint. If only one constraint, then case 2 (or 3) wouldn't be possible. But it is possible now. A possible use case as an example? (hmm... i'm trying my imagination hard now): Your sound needs low latency, so that could be a cause for the qos-latency constraint. And unblocking suspend could nonetheless happen: For example... you have an firefox open and don't want to prevent suspend for that case when the display is turned off Cheers, Flo -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
