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Date:	Thu, 06 Feb 2014 14:22:10 +0100
From:	"Rafael J. Wysocki" <>
To:	Linux PM list <>
Cc:	ACPI Devel Maling List <>,
	LKML <>,
	Mika Westerberg <>
Subject: [PATCH v3 0/6] PM / QoS: Introduce latency tolerance device PM QoS type

On Thursday, January 23, 2014 02:34:59 PM Rafael J. Wysocki wrote:
> On Friday, January 17, 2014 03:42:13 PM Rafael J. Wysocki wrote:
> > Hi All,
> > 
> > On some platforms hardware may switch to an energy-saving mode on the fly
> > on the basis of certain utilization metrics used by it.  That usually is
> > desirable from the energy conservation standpoint, but it generally causes
> > latencies to increase which may adversely affect some operations.  For this
> > reason, the platforms in question usually provide some interfaces for software
> > to indicate its latency tolerance and possibly to prevent the energy-saving
> > modes from being selected too aggressively.
> > 
> > The following series of patches introduces a device PM QoS type allowing
> > those interfaces to be used by kernel code and user space.  It is designed
> > in analogy with the existing resume latency device PM QoS type, which allows
> > some pieces of the existing device PM QoS code to be re-used and makes the
> > new user space interface fit into the existing framework.
> > 
> > Patch [1/5] modifies the names of symbols, variables, functions and structure
> > fields associated with the existing resume latency device PM QoS type to
> > avoid any confusion with the new one introduced by the subsequent patches.
> > 
> > Patch [2/5] introduces a new field in struct pm_qos_constraints for specifying
> > a special value to be returned as the effective requirement when the given list
> > of PM QoS requirements is empty.  That field is necessary for the new latency
> > tolerance device PM QoS type.
> > 
> > Patch [3/5] introduces the latency tolerance device PM QoS type along with
> > documentation.
> > 
> > Patch [4/5] modifies the ACPI LPSS (Low-Power Subsystem) driver to hook up
> > LPSS devices to the new latency tolerance device PM QoS interface.
> > 
> > Patch [5/5] modifies the dev_pm_qos_add_ancestor_request() routine so that it
> > can be used by drivers of devices without hardware latency tolerance support
> > for specifying their requirements via the ancestors of those devies.
> As usual, testing uncovered some issues, so an updated series follows.

OK, no comments - no objections.  Cool! :-)

Time for a non-RFC submission I guess.

The following series is almost the same as the previous one except for patch
[5/6] that fixes a bug (LPSS_LTR_SNOOP_REQ has to be set along with
LPSS_LTR_SNOOP_LAT_1US) and introduces a cutoff value such that all above it
will mean "no requirement".


I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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