path: root/Documentation
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authorRajneesh Bhardwaj <>2016-05-26 14:41:19 +0530
committerDarren Hart <>2016-05-27 11:47:56 -0700
commitb740d2e9233cb33626d3b62210bcfc6a34baa839 (patch)
treebb0ed870f77fef2bffaded52040e174578bd6caa /Documentation
parentff8651237f39cea60dc89b2d9f25d9ede3fc82c0 (diff)
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. 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 <> Signed-off-by: Vishwanath Somayaji <> Reviewed-by: Andy Shevchenko <> Signed-off-by: Darren Hart <>
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