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    SubjectRe: Attempted summary of suspend-blockers LKML thread
    On Thu, 5 Aug 2010, Brian Swetland wrote:

    > On Thu, Aug 5, 2010 at 6:01 PM, <> wrote:
    >> On Thu, 5 Aug 2010, Brian Swetland wrote:
    >>> On Thu, Aug 5, 2010 at 5:16 PM,  <> wrote:
    >>>>>> So for an mp3 playback, does an Android suspend between data fetches?
    >>>>> It can if the latency is long enough (which is why I point out low
    >>>>> power audio which is usually high latency).  For low latency (system
    >>>>> sounds, etc) 10-25ms between buffers it's not practical to fully
    >>>>> suspend but we will go to the lowest power state in idle if possible.
    >>>> the playback is able to continue even with all the clocks stopped? that
    >>>> surprises me. I would hav expected it to be able to sleep while playing
    >>>> audio, but not do a full suspend.
    >>> Obviously not all clocks are stopped (the DSP and codec are powered
    >>> and clocked, for example), but yeah we can clock gate and power gate
    >>> the cpu and most other peripherals while audio is playing on a number
    >>> of ARM SoC designs available today (and the past few years).
    >> does this then mean that you have multiple variations of suspend?
    >> for example, one where the audio stuff is left powered, and one where it
    >> isn't?
    > While the cpu (and the bulk of the system) is suspended, it's not
    > uncommon for some peripherals to continue to operate -- for example a
    > cellular radio, gps, low power audio playback, etc. Details will vary
    > depending on the SoC and board design. It's not so much a different
    > suspend mode (the system is still suspended), just a matter of whether
    > a peripheral can operate independently (and if it is lower power for
    > it to do so).

    this helps, but isn't quite what I was trying to ask.

    on a given piece of hardware, does suspend always leave the same
    peripherals on, or do you sometimes power more things down than other
    times when suspending?

    David Lang
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