lkml.org 
[lkml]   [2010]   [May]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH]PM QOS refresh against next-20100430
On Mon 2010-05-03 10:42:50, Jonathan Corbet wrote:
> On Mon, 03 May 2010 09:40:11 -0700
> Kevin Hilman <khilman@deeprootsystems.com> 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


\
 
 \ /
  Last update: 2010-05-04 09:55    [W:0.055 / U:0.780 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site