Hi Guys, Sorry, I think the conversation went pretty far from my patch.
Concerning my original patch, do you have any more ideas or concerns? I'm not sure I have a clear idea what, if anything, needs to be changed. I was able to verify it on the TC2 platform without issue. Thanks again for all of your time. Sebastian On 22 May 2013 11:51, Sebastian Capella <sebastian.cape...@linaro.org>wrote: > Quoting Dave Martin (2013-05-22 11:22:36) > > Currently not. This partly depends on whether the target residency is > > supposed to be a hint about the rough order of magnitude of the expected > > idle period, or whether it's supposed to be a strict contract. > > > > In effect, I think it's a hint which steers the choice of powerdown > > state, rather than soemthing with a strong real-time guarantee attached > > to it. In that case shaving the firmware latency off this value before > > using it may not be worth it. If the specified target residency is > > small enough that this makes a significant difference, this suggests a > > very short period of actual powerdown, which may not outweigh its own > > overheads in terms of power-saving. > > > > Thanks Dave, Liviu, > > Sorry, you've caught me mixing terms and concepts. > > I agree, target residency to me also is more an estimate of the cost vs. > benefit for a state. > > The cstates also define a latency parameter that is used for limiting > selection of certain states by the governor. This is affected by QoS > constraints, which we use alot in embedded. This is the one needed for > realtime use that is tricky with host os' additional latency. > > Both latency and target residency would need some adjustment for > embedded mobile if we have additional overhead as it becomes very > important to squeeze this as much as possible. For latency, > microseconds count as we cannot allow a cstate which will fail to meet > our qos constraints. > > Thanks, > > Sebastian > >
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