ACPI Low Power S0 Idle capabilities are announced via FADT table and can
be used to inform the kernel about the presence of one or more Low Power
Idle (LPI) entries as descried in LPIT table. LPIT table can exist
independently even if the FADT S0 Idle flag is not set and thus it could
confuse user since the following cpuidle attributes are created.
/sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us
/sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us
Presence or absence of above attributes could mean that the given
platform supports S0ix state or not.
This change allows to create the above cpuidle attributes only if
FADT table supports Low Power S0 Idle.
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Export lpit_read_residency_count_address(), so that it can be used from
drivers built as module. With the recent changes, the builtin_pci
functionality of the intel_pmc_core driver is removed and now it can be
built as a module to read this exported interface to calculate the PMC base
address.
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: linux-acpi@vger.kernel.org
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Tested-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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>
