On Tue, Dec 15 2015 at 03:07 -0700, Marc Titinger wrote:
On 10/12/2015 17:53, Ulf Hansson wrote:
On 17 November 2015 at 23:37, Lina Iyer <lina.i...@linaro.org> wrote:
Similarly, devices can register power-states into the cluster domain, in
a manner consistent with idle-states.
I don't get this. Can you please elaborate?
Alexes addition of "power states" to the power domains was to have a
better representation of features of power controllers. For instance
QoS may prevent to enter/exit complete power-off, but setting the core
voltage to say 0.7v is feasible in terms of timing, and still better
than full-power-on etc... Hence the domain has a list of possible
states to chose upon, between full power-on and full-power-off, and
genpd will call the platform code for this.
Now, this patch maps the idle-states as possible power states for the
domain: upon the last CPU runtime_put, the domain can chose the
deepest
state that can be reached given the enter/exit time available, and
call the platform code for this. This selected state can be any of:
* cluster-sleep (power OFF)
* cluster-retention A (L2RAM retention for instance)
* cluster-retention B (some device is still on, like PMU or bus
analyzer, healthckeck IP etc...)
...
* cluster-on, but lower voltage A
* cluster-on, but lower voltage B
etc...
Put short: CPUs, like any other devices in the domain may register a
power state.
This is a attempt to address device-retention states for devices that
are not hooked to runtime-pm, but feature a retention state handled by
the same firmware that handles idle-states. For instance a L2 caches.
I guess whether devices may use runtime PM or not, they still can be
attached to a PM domain with multiple power states?
yes.
From what I understand, it seems like you want to have a constraint on a
domain state based on the device's idle state. This seems more like a
job for a governor. You could write a governor that chooses the domain
state based on these dependencies.
I am not sure this can be solved generically without increasing the
complexity of genpd idle states.
Thanks,
Lina
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