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Power-saving routines for L138?

Paul Singh
Expert 2750 points
Other Parts Discussed in Thread: OMAPL138, SYSBIOS

Hi,

The technical reference manual of omap L138 SPRUH77’s chapter 10 is entirely devoted into power management. For example, it mentions “ARM Wait-For-Interrupt” in section 10.6.1, which requires an assembly code of:

MCR p15, #0, <Rd>, c7, c0, #4

I am interested in knowing that is there a TI package something like “L138 power saving pack”, which implements and exemplifies the usage of various power saving modules? I have searched through the L138 starterware as well as the quickStartOMAPL1x_rCSL without success.

Appreciate any help.

 

Paul

  • 0
    TI__Guru** 116170 points

    Paul,

    It is a little unclear on exactly what may be the best document or software that I can point you to regarding power management as you do not mention what feature of power management you wish to implement in your application. Let me point you to two places where you may be able to find what you are looking for :

    The frequency scaling ( the PLL and PSC modification) that is described in that document can be found in the GEL files for C6748 or OMAPL138 EVM. The GEL file allows you to change the Frequency settings of the core, peripherals and the mDDR.

    If you wish to find out how power management is implemented in in a Linux environment, please refer to the following wiki:

    http://processors.wiki.ti.com/index.php/OMAP-L1_Linux_Drivers_Usage#Power_Management 

    For power management under BIOS please refer to the following docs:

    DSP/BIOS PWRM

    • PWRM Overview:  TMS320 DSP/BIOS v5.41 User’s Guide (SPRU423h, Section 4.6)
    • PWRM API Description: TMS320C6000 DSP/BIOS 5.x Application Programming Interface(API) Reference Guide (SPRU403q, Section 2.23)

     

    SYSBIOS PWRM is on the wiki

     SYSBIOS POWER Module and example(s)

    –        http://processors.wiki.ti.com/index.php/Power_Module_for_C6748_and_OMAP-L138

    In addition to this, if there is any other mode that you wish to implement, you can use the rCSL package header files to directly talk to the register described in that document.

    Regards,

    Rahul

     

  • 0 in reply to Rahul Prabhu
    Expert 2750 points

    Rahul,

    I am kindly of confused because of variety of support packages available for L138.

    The wiki page you mentioned titles “OMAP-L1 Linux Drivers Usage”

    Further directs to http://lxr.linux.no/linux+v2.6.32/Documentation/cpu-freq/ , a link I found lots of old (presumably) links dates back to 2009 and before. And the linux.no site seems to be an individually managed community initiative outside the purview of TI.

    In addition, there is also

    SDK: http://www.ti.com/tool/linuxsdk-omapl138

    PSP: http://processors.wiki.ti.com/index.php/Community_Linux_PSP_for_DA8x/OMAP-L1/AM1x

     

    In which one of them, preferably with a link, is the source for “cpu-freq” located?

     

    Paul

  • 0 in reply to Paul Singh
    TI__Guru** 116170 points

    Hi Paul,

    The unified linux software development kit for OMAPL138 is called DVSDK 4.x which can be found on the link that you mention for the SDK. This SDK contains the linux kernel, the psp package, DSP software components like DSP BIOS, DSPLINK, etc. So that would be one stop place for development on OMAPL138 under linux.

    The linux kernel that is used in the SDK is a version of the 2.6.37 linux mainline kernel that has been ported to OMAPL138 and so you see the documentation of kernel links to open source mainline linux kernel documentation but the OMAPL138 documentation can either be found on ti wikis and collateral found on ti.com. 

    Source for the cpufreq driver will be in the PSP package under linux-source/drivers/cpufreq. For linux specific questions, I would recommend posting on the Linux forums.

    Regards,

    Rahul

    PS: I have added links to Power management docs under BIOS to my earlier post

  • 0 in reply to Rahul Prabhu
    Expert 2750 points

    Rahul,

    The link of the dsp/bios power module is nice, I gonna look into it. Also thanks for the clarification on previous question.

    Paul

  • 0 in reply to Rahul Prabhu
    Expert 2750 points

    The answers above are correct.