Intel platforms use Low Power Idle Table (LPIT) to enumerate platform
Low Power Idle states. There are two types of low power residencies
a) CPU PKG C10 - read via MSR (Function fixed hardware interface)
b) Platform Controller Hub (PCH) SLP_S0 - read via memory mapped
Ref. https://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf
System sleep time (SLP_S0 signal asserted) is measured in ticks,
varies in every platform and based on PMC clock.
BUG=b:300440936
TEST=check kernel cpuidle sysfs for non-zero residency after s0ix cycle
and both must match
cat /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us
cat /sys/kernel/debug/pmc_core/slp_s0_residency_usec
Change-Id: I401dd4a09a67d81a9ea3a56cd22f1a681e2a9349
Signed-off-by: Sukumar Ghorai <sukumar.ghorai@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78164
Reviewed-by: Subrata Banik <subratabanik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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