linux-kernel - Re: [PATCH v7] platform:x86: Add PMC Driver for Intel Core SoC

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Date:	Thu, 26 May 2016 10:09:11 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>
Cc:	platform-driver-x86@...r.kernel.org,
	andriy.shevchenko@...ux.intel.com, linux-kernel@...r.kernel.org,
	olof@...om.net, tglx@...utronix.de, hpa@...or.com,
	dbasehore@...gle.com, vishwanath.somayaji@...el.com
Subject: Re: [PATCH v7] platform:x86: Add PMC Driver for Intel Core SoC

On Thu, May 26, 2016 at 02:41:19PM +0530, Rajneesh Bhardwaj wrote:
> 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@...el.com>
> Signed-off-by: Vishwanath Somayaji <vishwanath.somayaji@...el.com>

Queued for 4.7. Thank you.

-- 
Darren Hart
Intel Open Source Technology Center