On Tue, 24 Jul 2007, Benjamin Herrenschmidt wrote:
On Sun, 2007-07-22 at 10:26 -0700, Arjan van de Ven wrote:
On Sat, 2007-07-21 at 23:49 -0700, david@xxxxxxx wrote:
this approach would allow the transition of ALL drivers to the new mode of
operation in one fell swoop, and then adding additional power management
features is just adding to the existing list rather then implementing new
functions.
I have a concern with this approach though. It seems to assume that
there is one global thing somewhere that sets the system state; in my
experience that is the wrong approach; in fact there is a very definite
evidence that there are many decisions on power that are to be made
local at a high frequency. An example of this is the processor speed;
the ondemand governer does exactly this for the cpus that can switch
speeds fast; it's just impossible to beat such a local, fast decision
with anything on a global scale.
On the other hand, some things (the high level goals and constraints)
are obviously global.
I think we need a set of constraints that trickle down the power tree
and limit what a given driver can do locally.
what sort of contraints are you thinking of?
David Lang
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