en Copyright 2015 Java http://172.16.0.5:8080/history/linux-6.15/Documentation/ABI/testing/sysfs-devices-lpss_ltr#2e0f8822 ACPI / LPSS: Add support for exposing LTR registers to user spaceDevices on the Intel Lynxpoint Low Power Subsystem (LPSS) haveregisters providing access to LTR (Latency Tolerance Reporting)functionality that allows software to monitor and possibly influencethe aggressiveness of the platform's active-state power management.For each LPSS device, there are two modes of operation related to LTR,the auto mode and the software mode. In the auto mode the LTR isset up by the platform firmware and managed by hardware. Softwarecan only read the LTR register values to monitor the platform'sbehavior. In the software mode it is possible to use LTR to controlthe extent to which the platform will use its built-in powermanagement features.This changeset adds support for reading the LPSS devices' LTRregisters and exposing their values to user space for monitoring anddiagnostics purposes. It re-uses the MMIO mappings created to accessthe LPSS devices' clock registers for reading the values of the LTRregisters and exposes them to user space through sysfs deviceattributes. Namely, a new atrribute group, lpss_ltr, is created foreach LPSS device. It contains three new attributes: ltr_mode,auto_ltr, sw_ltr. The value of the ltr_mode attribute reflects theLTR mode being used at the moment (software vs auto) and the othertwo contain the actual register values (raw) whose meaning dependson the LTR mode. All of these attributes are read-only.Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> List of files: /linux-6.15/Documentation/ABI/testing/sysfs-devices-lpss_ltr Wed, 06 Mar 2013 22:46:28 +0000 Rafael J. Wysocki <rafael.j.wysocki@intel.com>