platform/x86: Add PMC Driver for Intel Core SoC

platform/x86: Add PMC Driver for Intel Core SoC

This patch adds the Power Management Controller driver as a PCI driver
for Intel Core SoC architecture.

This driver can utilize debugging capabilities and supported features
as exposed by the Power Management Controller.

Please refer to the below specification for more details on PMC features.
http://www.intel.in/content/www/in/en/chipsets/100-series-chipset-datasheet-vol-2.html

The current version of this driver exposes SLP_S0_RESIDENCY counter.
This counter can be used for detecting fragile SLP_S0 signal related
failures and take corrective actions when PCH SLP_S0 signal is not
asserted after kernel freeze as part of suspend to idle flow
(echo freeze > /sys/power/state).

Intel Platform Controller Hub (PCH) asserts SLP_S0 signal when it
detects favorable conditions to enter its low power mode. As a
pre-requisite the SoC should be in deepest possible Package C-State
and devices should be in low power mode. For example, on Skylake SoC
the deepest Package C-State is Package C10 or PC10. Suspend to idle
flow generally leads to PC10 state but PC10 state may not be sufficient
for realizing the platform wide power potential which SLP_S0 signal
assertion can provide.

SLP_S0 signal is often connected to the Embedded Controller (EC) and the
Power Management IC (PMIC) for other platform power management related
optimizations.

In general, SLP_S0 assertion == PC10 + PCH low power mode + ModPhy Lanes
power gated + PLL Idle.

As part of this driver, a mechanism to read the SLP_S0_RESIDENCY is exposed
as an API and also debugfs features are added to indicate SLP_S0 signal
assertion residency in microseconds.

echo freeze > /sys/power/state
wake the system
cat /sys/kernel/debug/pmc_core/slp_s0_residency_usec

Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>
Signed-off-by: Vishwanath Somayaji <vishwanath.somayaji@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>