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i.MX28 regulator operating modes for Linux

Question asked by lategoodbye on May 31, 2015
Latest reply on Jun 2, 2015 by igorpadykov



i'm still working on regulator support for Linux Mainline and have some questions about the LINREGs and DC-DC on the i.MX28 PMU.


1. Which of the Linux modes (see below) could be mapped for LINREGs and DC-DC?


2. Looking at the FSL BSP (2.6.35) shows that FAST mode for LINREGs is implemented as DISABLE_STEPPING=1. Is the implementation correct?


3. Are there any useful LINREG settings for idle state?


4. What are the relevant DC-DC settings for the Linux regulator modes?


Here is a quote of the possible operating modes of a regulator (this includes also the DC-DC):



* Regulator operating modes.


* Regulators can run in a variety of different operating modes depending on

* output load. This allows further system power savings by selecting the

* best (and most efficient) regulator mode for a desired load.


* Most drivers will only care about NORMAL. The modes below are generic and

* will probably not match the naming convention of your regulator data sheet

* but should match the use cases in the datasheet.


* In order of power efficiency (least efficient at top).


* Mode Description

* FAST Regulator can handle fast changes in it's load.

* e.g. useful in CPU voltage & frequency scaling where

* load can quickly increase with CPU frequency increases.


* NORMAL Normal regulator power supply mode. Most drivers will

* use this mode.


* IDLE Regulator runs in a more efficient mode for light

* loads. Can be used for devices that have a low power

* requirement during periods of inactivity. This mode

* may be more noisy than NORMAL and may not be able

* to handle fast load switching.


* STANDBY Regulator runs in the most efficient mode for very

* light loads. Can be used by devices when they are

* in a sleep/standby state. This mode is likely to be

* the most noisy and may not be able to handle fast load

* switching.



Thanks in advance