Re: [PATCH 0/8] Suspend block api (version 6)

[Kevin Hilman]

"Rafael J. Wysocki" <rjw@xxxxxxx> writes:

> On Tuesday 04 May 2010, Mark Brown wrote:
>> On Tue, May 04, 2010 at 11:06:39AM -0700, Kevin Hilman wrote:
>> 
>> > With opportunistic suspend, all of this flexibility is gone, and the
>> > device/subsystem is told to go into the lowest power, highest latency
>> > state, period.
>> 
>> Well, half the problem I have is that unfortunately it's not a case of
>> doing that period.  The prime example I'm familiar with is that for
>> understandable reasons users become irate when you power down the audio
>> CODEC while they're in the middle of a call so if opportunistic PM is in
>> use then the audio subsystem needs some additional help interpreting a
>> suspend request so that it can figure out how to handle it.  Similar
>> issues apply to PMICs, though less pressingly for various reasons.
>> 
>> Just to be clear, I do understand and mostly agree with the idea that
>> opportunistic suspend presents a reasonable workaround for our current
>> inability to deliver good power savings with runtime PM methods on many
>> important platforms but I do think that if we're going to make this
>> standard Linux PM functionality then we need to be clearer about how
>> everything is intended to hang together.
>
> At the moment the rule of thumb is: if you don't need the opportunistic
> suspend, don't use it.  It is not going to be enabled by default on anything
> other than Android right now.

Sure, but there are driver authors and subsystem maintainers who care
about optimal PM in "normal" Linux *and* in Android.

As a PM maintainer for an embedded platform (OMAP) used in both, I
certainly care about both, so "disable it if you don't like it" is not
really an option.

IMO, driver/subsystem authors should not have to care if the userspace
is Android or not.  We should be working towards a world where Android
is not a special case.

Kevin
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