lkml.org 
[lkml]   [2014]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC/RFT][PATCH v2 0/6] PM / QoS: Introduce latency tolerance device PM QoS type
On Thu, Jan 23, 2014 at 02:34:59PM +0100, 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.

I tested this series on HSWULT and adding/removing QoS LTR requests from
both userspace and from a modified i2c-hid driver (calling
dev_pm_qos_add_ancestor_request()) and seems to work nicely -- When I read
back the HW LTR values they are what is expected.

Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>


\
 
 \ /
  Last update: 2014-01-24 16:41    [W:0.901 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site