Re: [GIT PULL] ACPI and power management fixes for v3.9-rc1

Nishanth Menon
2013-02-26T16:10:56Z

On 16:55-20130226, Rafael J. Wysocki wrote:
> On Monday, February 25, 2013 09:31:45 PM Linus Torvalds wrote:
> > On Mon, Feb 25, 2013 at 7:17 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
[..]
>
> > This has become a huge problem, to the point that we have a
> > "Documentation/power/opp.txt" file THAT NEVER CLEARLY STATES WHAT THE
> > F*CK OPP ACTUALLY MEANS! What nice "documentation".
>
> It says that in "Introduction", but it would be clearer if the title of the
> doc was something like "Operating Performance Points (OPP) Library". Nishanth?
Yes indeed. Will the following help? I can post it as an official patch
if the direction is proper.
diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt
index 3035d00..4a17443 100644
--- a/Documentation/power/opp.txt
+++ b/Documentation/power/opp.txt
@@ -1,5 +1,5 @@
*=============*
-* OPP Library *
+* Operating Performance Points (OPP) Library *
*=============*

(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated
@@ -16,6 +16,8 @@ Contents

1. Introduction
===============
+1.1 What is an Operating Performance Point (OPP)?
+
Complex SoCs of today consists of a multiple sub-modules working in conjunction.
In an operational system executing varied use cases, not all modules in the SoC
need to function at their highest performing frequency all the time. To
@@ -25,6 +27,16 @@ more. The set of discrete tuples consisting of frequency and voltage pairs that
the device will support per domain are called Operating Performance Points or
OPPs.

+As an example:
+MPU device supports {300MHz at minimum voltage of 1V}, {800MHz at minimum
+voltage of 1.2V}, {1GHz at minimum voltage of 1.3V}
+We can represent these as three OPPs
+{300000, 1000000}
+{800000, 1200000}
+{1000000, 1300000}
+
+1.2 Operating Performance Points Library
+
OPP library provides a set of helper functions to organize and query the OPP
information. The library is located in drivers/base/power/opp.c and the header
is located in include/linux/opp.h. OPP library can be enabled by enabling

--
Regards,
Nishanth Menon