On Wed, 25 Jul 2007, Benjamin Herrenschmidt wrote:
On Tue, 2007-07-24 at 13:14 -0700, david@xxxxxxx wrote:
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?
A parent power state defines what states children can be in. For
example. A way to express those dependencies would be nice. Or
alternatiely, the power state of all the children defines the power
state a parent can go in automatically.
Ok, I see tow things here.
1. do you really want to try and propogate things like this from one to
the other, or would it be good enough to flag the issue and let the
software selecting the modes implement this contraint?
2. how can you standardize the requirements?
at the very least you have
for this mode all children must be off
for this mode all children must be in a mode that includes a 'suspended'
flag (this could be made implicit by saying that you must suspend children
before parents) and then just flagging the 'suspended, but not off' modes)
what requirements are needed? (I'm sure that there are others, but
hopefully it's possible to avoid requirements like 'the clock speed for
device A must be >X to allow device B to operate in mode Y')
David Lang
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