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| -rw-r--r-- | Documentation/power/opp.txt | 25 |
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| 1 | *=============* | 1 | Operating 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 | ||
| 17 | 1. Introduction | 16 | 1. Introduction |
| 18 | =============== | 17 | =============== |
| 18 | 1.1 What is an Operating Performance Point (OPP)? | ||
| 19 | |||
| 19 | Complex SoCs of today consists of a multiple sub-modules working in conjunction. | 20 | Complex SoCs of today consists of a multiple sub-modules working in conjunction. |
| 20 | In an operational system executing varied use cases, not all modules in the SoC | 21 | In an operational system executing varied use cases, not all modules in the SoC |
| 21 | need to function at their highest performing frequency all the time. To | 22 | need to function at their highest performing frequency all the time. To |
| 22 | facilitate this, sub-modules in a SoC are grouped into domains, allowing some | 23 | facilitate this, sub-modules in a SoC are grouped into domains, allowing some |
| 23 | domains to run at lower voltage and frequency while other domains are loaded | 24 | domains to run at lower voltage and frequency while other domains run at |
| 24 | more. The set of discrete tuples consisting of frequency and voltage pairs that | 25 | voltage/frequency pairs that are higher. |
| 26 | |||
| 27 | The set of discrete tuples consisting of frequency and voltage pairs that | ||
| 25 | the device will support per domain are called Operating Performance Points or | 28 | the device will support per domain are called Operating Performance Points or |
| 26 | OPPs. | 29 | OPPs. |
| 27 | 30 | ||
| 31 | As an example: | ||
| 32 | Let 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 | |||
| 36 | We can represent these as three OPPs as the following {Hz, uV} tuples: | ||
| 37 | {300000000, 1000000} | ||
| 38 | {800000000, 1200000} | ||
| 39 | {1000000000, 1300000} | ||
| 40 | |||
| 41 | 1.2 Operating Performance Points Library | ||
| 42 | |||
| 28 | OPP library provides a set of helper functions to organize and query the OPP | 43 | OPP library provides a set of helper functions to organize and query the OPP |
| 29 | information. The library is located in drivers/base/power/opp.c and the header | 44 | information. The library is located in drivers/base/power/opp.c and the header |
| 30 | is located in include/linux/opp.h. OPP library can be enabled by enabling | 45 | is located in include/linux/opp.h. OPP library can be enabled by enabling |
