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Some advice about MMU on the OMAP-L138 and SYSBIOS...

Mike Geppert
Expert 1980 points

It seems like the MMU module makes several units on the OMAP unaccessable by default. EMIF as an example.

We have a need to access this section to set it up.  Looking for directions how to get the MMU unit and our code to play nice together.

1) We could pull our init code for the EMIF and try to move it into the startup routines in the cfg file.  Doesnt seem to be easy to do with the GUI on CCS.

2) Can we disable the MMU and then call our init routines and then restart the MMU?

3) Build our own MMU routines (not my favorit choise) so that the EMIF is accessable?  Documentation seems to be weak on the attributes like bufferable verses cacheable.

Also it looks like the ARM and the DSP have very different views of the MMU.  We plan to do all the MMU managment on the ARM.  Any issues with that?

Thanks,

 

  • 0
    TI__Mastermind 30830 points

    Mike,

    I think you just need to override the default MMU table entry for the EMIF address space.

    Here is an example of how to configure an MMU table entry to allow access to the peripheral memory space beginning at address 0xa0400000:

     var Mmu = xdc.useModule('ti.sysbios.family.arm.arm9.Mmu'); 

     // Force peripheral section to be NON cacheable 
     var peripheralAttrs = { type : Mmu.FirstLevelDesc_SECTION, // SECTION descriptor 
     bufferable : false, // bufferable 
     cacheable : false, // cacheable 
     };

     // Define the base address of the 1 Meg page 
     // the peripheral resides in.  
     var peripheralBaseAddr = 0xa0400000; /* replace with the 1 meg page address of your peripheral */      

     // Configure the corresponding MMU page descriptor accordingly 
     Mmu.setFirstLevelDescMeta(peripheralBaseAddr, peripheralBaseAddr, peripheralAttrs); 

    SYS/BIOS only supports configuring the MMU from the ARM side.

    I hope this helps.

    Alan
  • 0 in reply to Alan DeMars
    Expert 1980 points

    Thanks!

    Worked like a champ...