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@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
