How to use generic power domains (pm_genpd)

[Rickard Andersson <rickard.andersson@stericsson.com>]

Hi,

I am currently looking at genpd to see if it can be used in my case
(U8500) and I have some questions.

I want to model a powerdomain that is tied to the CPU (the CPU can not
be turned on without this power domain being on) so I would like to use
pm_genpd_attach_cpuidle(..). One problem with using this function is
that my powerdomain can be attached to several cpuidle sleep states and
genpd does not seem to handle that case? (genpd does only seem to handle
being connected to one cpuidle state.)

Another thing that I am trying to find out is if genpd works ok if a
driver in the power domain does pm_runtime_get_sync(..) in interrupt
context? When looking at pm_genpd_runtime_resume(..) it looks like the
function will never call __pm_genpd_poweron(..) in the interrupt context
case. If I understand it correctly this means that the cpuidle
connection code "genpd->cpu_data->idle_state->disabled = true" is never
executed?
Also in __pm_genpd_poweron(..) it seems non otimal from power
consumption point of view to call cpuidle_pause_and_lock(..) as soon as
the cpuidle connected power domain is turned on because
cpuidle_pause_and_lock(..) calls kick_all_cpus_sync(). This means that
all CPU's in sleep will be woken up just because another CPU enables
this power domain.

Thanks in advance
Rickard