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-rw-r--r--Documentation/power/opp.txt25
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1*=============* 1Operating Performance Points (OPP) Library
2* OPP Library * 2==========================================
3*=============*
4 3
5(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated 4(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated
6 5
@@ -16,15 +15,31 @@ Contents
16 15
171. Introduction 161. Introduction
18=============== 17===============
181.1 What is an Operating Performance Point (OPP)?
19
19Complex SoCs of today consists of a multiple sub-modules working in conjunction. 20Complex SoCs of today consists of a multiple sub-modules working in conjunction.
20In an operational system executing varied use cases, not all modules in the SoC 21In an operational system executing varied use cases, not all modules in the SoC
21need to function at their highest performing frequency all the time. To 22need to function at their highest performing frequency all the time. To
22facilitate this, sub-modules in a SoC are grouped into domains, allowing some 23facilitate this, sub-modules in a SoC are grouped into domains, allowing some
23domains to run at lower voltage and frequency while other domains are loaded 24domains to run at lower voltage and frequency while other domains run at
24more. The set of discrete tuples consisting of frequency and voltage pairs that 25voltage/frequency pairs that are higher.
26
27The set of discrete tuples consisting of frequency and voltage pairs that
25the device will support per domain are called Operating Performance Points or 28the device will support per domain are called Operating Performance Points or
26OPPs. 29OPPs.
27 30
31As an example:
32Let us consider an MPU device which supports the following:
33{300MHz at minimum voltage of 1V}, {800MHz at minimum voltage of 1.2V},
34{1GHz at minimum voltage of 1.3V}
35
36We can represent these as three OPPs as the following {Hz, uV} tuples:
37{300000000, 1000000}
38{800000000, 1200000}
39{1000000000, 1300000}
40
411.2 Operating Performance Points Library
42
28OPP library provides a set of helper functions to organize and query the OPP 43OPP library provides a set of helper functions to organize and query the OPP
29information. The library is located in drivers/base/power/opp.c and the header 44information. The library is located in drivers/base/power/opp.c and the header
30is located in include/linux/opp.h. OPP library can be enabled by enabling 45is located in include/linux/opp.h. OPP library can be enabled by enabling