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Add functionality to read LPIT table, which provides: - Sysfs interface to read residency counters via /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us Here the count "low_power_idle_cpu_residency_us" shows the time spent by CPU package in low power state. This is read via MSR interface, which points to MSR for PKG C10. Here the count "low_power_idle_system_residency_us" show the count the system was in low power state. This is read via MMIO interface. This is mapped to SLP_S0 residency on modern Intel systems. This residency is achieved only when CPU is in PKG C10 and all functional blocks are in low power state. It is possible that none of the above counters present or anyone of the counter present or all counters present. For example: On my Kabylake system both of the above counters present. After suspend to idle these counts updated and prints: 6916179 6998564 This counter can be read by tools like turbostat to display. Or it can be used to debug, if modern systems are reaching desired low power state. - Provides an interface to read residency counter memory address This address can be used to get the base address of PMC memory mapped IO. This is utilized by intel_pmc_core driver to print more debug information. In addition, to avoid code duplication to read iomem, removed the read of iomem from acpi_os_read_memory() in osl.c and made a common function acpi_os_read_iomem(). This new function is used for reading iomem in in both osl.c and acpi_lpit.c. Link: http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.