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    SubjectRe: [PATCH 0/8] Suspend block api (version 6)
    On Mon, May 03, 2010 at 09:40:26AM -0700, Kevin Hilman wrote:

    > At least from the kernel perspective, both suspend blockers and
    > runtime PM have the same goal. Given that, which framework should the
    > driver writer target? Both? Seems like duplicate effort. Using
    > suspend blockers assumes the system is in opportunitstic suspend mode
    > and (at least in the keypad example given) assumes a suspend-blocker
    > aware userspace (Android.) Without both, targeted power savings will
    > not be acheived.

    The other concern here is that for many mobile systems the actual
    semantic intended by "suspend" as it's currently used is more runtime PM
    like than full suspend - the classic example of this is that when
    suspending while on a call in a phone you don't want to suspend the
    modem or audio CODEC, you want to leave them running. If you use a full
    system suspend then the drivers for affected components have to play
    guessing games (or add currently non-standard knobs for apps to twiddle)
    to decide if the system intends them to actually implement the suspend
    or not but with runtime PM it all falls out very naturally without any
    effort on the part of the driver.

    > To me, runtime PM is a generic and flexible approach that can be used
    > with any userspace. Driver writers should not have to care whether
    > the system is in "opportunistic" mode or about whether userspace is
    > suspend blocker capable. They should only have to think about when
    > the device is (or should be) idle.

    I fully agree with this. We do need to ensure that a runtime PM based
    system can suspend the CPU core and RAM as well as system suspend can
    but that seems doable.

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