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authorDavid S. Miller <davem@davemloft.net>2013-03-12 13:52:22 +0400
committerDavid S. Miller <davem@davemloft.net>2013-03-12 13:52:22 +0400
commite5f2ef7ab4690d2e8faaf5fd203c5ecd70c3abaf (patch)
tree3558f68717c70a67e18c3274bb17709a353d036f /Documentation/power/opp.txt
parent30129cf28a5c99f9cb7c168f0d280f147fd6cc8b (diff)
parent3da889b616164bde76a37350cf28e0d17a94e979 (diff)
downloadlinux-e5f2ef7ab4690d2e8faaf5fd203c5ecd70c3abaf.tar.xz
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Conflicts: drivers/net/ethernet/intel/e1000e/netdev.c Minor conflict in e1000e, a line that got fixed in 'net' has been removed in 'net-next'. Signed-off-by: David S. Miller <davem@davemloft.net>
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@@ -1,6 +1,5 @@
-*=============*
-* OPP Library *
-*=============*
+Operating Performance Points (OPP) Library
+==========================================
(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated
@@ -16,15 +15,31 @@ 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
facilitate this, sub-modules in a SoC are grouped into domains, allowing some
-domains to run at lower voltage and frequency while other domains are loaded
-more. The set of discrete tuples consisting of frequency and voltage pairs that
+domains to run at lower voltage and frequency while other domains run at
+voltage/frequency pairs that are higher.
+
+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:
+Let us consider an MPU device which supports the following:
+{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 as the following {Hz, uV} tuples:
+{300000000, 1000000}
+{800000000, 1200000}
+{1000000000, 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