Locking in the clk API

[skannan@codeaurora.org (Saravana Kannan)]

On 01/11/2011 04:18 AM, Paul Mundt wrote:
> Again, you are approaching it from the angle that an atomic clock is a
> special requirement rather than the default behaviour. Sleeping for
> lookup, addition, and deletion are all quite acceptable, but
> enable/disable pairs have always been intended to be usable from atomic
> context. Anyone that doesn't count on that fact is either dealing with
> special case clocks (PLLs, root clocks, etc.) or simply hasn't bothered
> implementing any sort of fine grained runtime power management for their
> platform.

Paul,

I see you repeating this point a couple of times and I'm a bit confused 
how you handle the clock tree/dependencies.

Does your clock driver NOT hide the details of what root clock/PLL a 
branch clock is sourced from? If you do hide the details of the root/PLL 
source, how do you get the branch clk_enable() to be done atomically if 
the root/PLL enables are not possible in atomic context?

Is it simply a matter of your hardware having PLLs and root clocks that 
can be turned on/off quickly?

-Saravana

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