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    SubjectRe: [PATCH 0/8] Suspend block api (version 6)
    On Monday 03 May 2010, Mark Brown wrote:
    > 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.

    I _think_ it would be hard at least. On ACPI-based systems it's not doable at
    all AFAICS.

    However, the real question is whether or not the opportunistic suspend feature
    is worth adding to the kernel as such and I think it is.

    To me, it doesn't duplicate the runtime PM framework which is aimed at the power
    management of individual devices rather than the system as a whole.


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