On Mon 2010-05-03 10:42:50, Jonathan Corbet wrote: > On Mon, 03 May 2010 09:40:11 -0700 > Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> wrote: > > > > One question, though... one clear use of this API is for drivers to > > > say "don't go into C3 or deeper because things go wrong"; I'm about to > > > add another one of those. It works, but the use of a > > > PM_QOS_CPU_DMA_LATENCY requirement with a hard-coded number that one > > > hopes is small enough seems a bit...indirect. I wonder if it would be > > > clearer and more robust to add a new requirement^Wrequest type saying > > > "the quality of service I need is shallow sleeps only"? > > > > The problem with that is portability. > > > > What does "shallow" mean? > > Well, shallow could mean that the state lacks the CPUIDLE_FLAG_DEEP > flag; that should be relatively portable. In any case, it seems more > so than "if I put in a 55us latency requirement, I'll stay out of C3". While C3 has maximum allowed latency (101usec, iirc), I believe there's no minimum, so someone could create platform with really quick C3 with perhaps only 10usec to enter... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
