linux-kernel - [PATCH 14/15] hwmon, fam15h_power: add documentation for accumulated power algorithm

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Date:	Thu, 27 Aug 2015 16:07:45 +0800
From:	Huang Rui <ray.huang@....com>
To:	Borislav Petkov <bp@...e.de>, Jean Delvare <jdelvare@...e.de>,
	"Guenter Roeck" <linux@...ck-us.net>,
	Andy Lutomirski <luto@...capital.net>,
	"Andreas Herrmann" <herrmann.der.user@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	John Stultz <john.stultz@...aro.org>,
	Frédéric Weisbecker <fweisbec@...il.com>
CC:	<lm-sensors@...sensors.org>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>,
	Andreas Herrmann <herrmann.der.user@...glemail.com>,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	Borislav Petkov <bp@...en8.de>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>, Tony Li <tony.li@....com>,
	Huang Rui <ray.huang@....com>
Subject: [PATCH 14/15] hwmon, fam15h_power: add documentation for accumulated power algorithm

This patch adds the description to explain the accumulated power
algorithm.

Signed-off-by: Huang Rui <ray.huang@....com>
---
 Documentation/hwmon/fam15h_power | 45 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/Documentation/hwmon/fam15h_power b/Documentation/hwmon/fam15h_power
index 42bf04e..dc2bc69 100644
--- a/Documentation/hwmon/fam15h_power
+++ b/Documentation/hwmon/fam15h_power
@@ -45,3 +45,48 @@ This driver provides ProcessorPwrWatts and CurrPwrWatts:
 On multi-node processors the calculated value is for the entire
 package and not for a single node. Thus the driver creates sysfs
 attributes only for internal node0 of a multi-node processor.
+
+2) Accumulated Power Mechanism
+
+This driver also introduces an algorithm that should be used to
+calculate the average power consumed by a processor during a
+measurement interval Tm. The feature of accumulated power mechanism is
+indicated by CPUID Fn8000_0007_EDX[12].
+
+* Tsample: compute unit power accumulator sample period
+* Tref: the PTSC counter period
+* PTSC: performance timestamp counter
+* N: the ratio of compute unit power accumulator sample period to the
+  PTSC period
+* Jmax: max compute unit accumulated power which is indicated by
+  MaxCpuSwPwrAcc MSR C001007b
+* Jx/Jy: compute unit accumulated power which is indicated by
+  CpuSwPwrAcc MSR C001007a
+* Tx/Ty: the value of performance timestamp counter which is indicated
+  by CU_PTSC MSR C0010280
+* PwrCPUave: CPU average power
+
+i. Determine the ratio of Tsample to Tref by executing CPUID Fn8000_0007.
+	N = value of CPUID Fn8000_0007_ECX[CpuPwrSampleTimeRatio[15:0]].
+
+ii. Read the full range of the cumulative energy value from the new
+MSR MaxCpuSwPwrAcc.
+	Jmax = value returned.
+iii. At time x, SW reads CpuSwPwrAcc MSR and samples the PTSC.
+	Jx = value read from CpuSwPwrAcc and Tx = value read from
+PTSC.
+
+iv. At time y, SW reads CpuSwPwrAcc MSR and samples the PTSC.
+	Jy = value read from CpuSwPwrAcc and Ty = value read from
+PTSC.
+
+v. Calculate the average power consumption for a compute unit over
+time period (y-x). Unit of result is uWatt.
+	if (Jy < Jx) // Rollover has occurred
+		Jdelta = (Jy + Jmax) - Jx
+	else
+		Jdelta = Jy - Jx
+	PwrCPUave = N * Jdelta * 1000 / (Ty - Tx)
+
+This driver provides PwrCPUave:
+* power1_acc (PwrCPUave)
-- 
1.9.1

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