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    SubjectRe: Locking in the clk API
    On 01/11/2011 01:16 AM, Russell King - ARM Linux wrote:
    > On Tue, Jan 11, 2011 at 10:16:42AM +0800, Jeremy Kerr wrote:
    >> At present, we can satisfy these with:
    >>
    >> * clk_enable: may sleep
    >
    > I object to this as one of the purposes behind the clk API is to allow
    > power savings to be made, and unless we can perform clk enable/disable
    > from atomic contexts, the best you can do is enable the clock when the
    > device is probed and disable it when it's released.

    Since dev_pm_ops.suspend is not atomic anymore (am I wrong?), what is
    the atomic context that you are having in mind that's related to power
    savings? How often do we really need to call clk enable/disable in that
    atomic context?

    If the system VDD needed to be increased when a clock/core in enabled
    (in reality, when a core is enabled), how do we make sure that the
    voltage is reduced when the clock/core is turned off? Do we simply punt
    the voltage change problem to the driver and say "not our problem"?

    I'm not saying that the voltage change should or shouldn't be handled by
    the clock driver. But it looks like the same methods used to handle the
    voltage change problem could be applied to how we could handle the clk
    enable/disable problem.

    -Saravana

    --
    Sent by an employee of the Qualcomm Innovation Center, Inc.
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.


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