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    SubjectRe: [PATCH] CPU C-state breakage with PM Qos change
    On Fri, Feb 03, 2012 at 03:04:43PM +0100, Pihet-XID, Jean wrote:
    > Looping in linux-pm
    >
    > On Fri, Feb 3, 2012 at 1:14 AM, Venkatesh Pallipadi <venki@google.com> wrote:
    > > Looks like change "PM QoS: Move and rename the implementation files"
    > > made pm_qos depend on CONFIG_PM which depends on
    > > PM_SLEEP || PM_RUNTIME
    > >
    > > That breaks CPU C-states with kernels not having these CONFIGs, causing CPUs
    > > to spend time in Polling loop idle instead of going into deep C-states,
    > > consuming way way more power. This is with either acpi idle or intel idle
    > > enabled.
    > >
    > > Either CONFIG_PM should be enabled with any pm_qos users or
    > > the !CONFIG_PM pm_qos_request() should return sane defaults not to break
    > > the existing users. Here's is the patch for the latter option.
    > I think the real question is whether PM QoS should be functional in
    > all cases (as is ACPI) or whether only if certain options are set
    > (CONFIG_PM).
    > In the current code if CONFIG_PM is not enabled, a dummy PM QoS API is
    > provided as function stubs in order for the build to succeed.
    >
    > Rafael, Mark,
    > What do you think? Should PM QoS be enabled in all cases? Are there
    > any known dependencies with CONFIG_PM?

    Yes I do think pm_qos interfaces should be enabled all the time and be
    independent of CONFIG_PM. Also, I still am not a fan of the renaming
    patch but, as the argument for and against renaming cannot be based on
    quantifiable things I've chosen not to let it bother me.

    I think Venki's change is a band aid and we should fix it right by not
    having a dependency on config_pm for the interface to behave.

    I'll take a look at why there is now a dependency before I have more to
    say.

    --mark


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