How to map MSM as uncached memory?

Hi Clemens,

for CPU access, you have to configure the MPAX unit within each CorePac. 32-bit logical addresses are translated into 36-bit physical addresses in this unit (see Memory Map Summary in the device Data Manual for address ranges). There are 16 segment register pairs available. At power-up, segments 0 and 1 are configured with default values for access to all system memory (Seg. 0: 0x00000000...0x7FFFFFFF and Seg. 1: 0x80000000...0xFFFFFFFF > DDR3). Segments with higher numbers have higher priority. Therefore, smaller segments with higher priorities can be placed within a larger segment with lower priority.

Example:

#include <ti/csl/csl_xmc.h>
#include <ti/csl/csl_xmcAux.h>

// Helper function for configuration of a XMC MPAX segment
int SetXMC_MPAX(int mapIndex, unsigned int localAddress, unsigned long long physAddress, unsigned int segSize)
{
    CSL_XMC_XMPAXH mpaxh;
    CSL_XMC_XMPAXL mpaxl;

    if (mapIndex < 0)
    {
        // Search for a free segment
        for (mapIndex=2; mapIndex<16; mapIndex++)
        {
            CSL_XMC_getXMPAXH(mapIndex, &mpaxh);
            if (mpaxh.segSize == 0)
                break;
        }
        if (mapIndex == 16)
            return -1;
    }

    mpaxl.ux    = 1;
    mpaxl.uw    = 1;
    mpaxl.ur    = 1;
    mpaxl.sx    = 1;
    mpaxl.sw    = 1;
    mpaxl.sr    = 1;
    mpaxl.rAddr = physAddress >> 12;
    mpaxh.bAddr = localAddress >> 12;
    mpaxh.segSize = (segSize == 0) ? 0 : (30 - _lmbd(1, segSize));
    CSL_XMC_setXMPAXL(mapIndex, &mpaxl);
    CSL_XMC_setXMPAXH(mapIndex, &mpaxh);

    return mapIndex;
}

void InitSegments()
{
    // Place 4MB of MSM at address 0x50000000 using a free segment index
    SetXMC_MPAX(-1, 0x50000000, 0x0C000000, 4<<20 /*4 MB*/);
}

The segment size needs to be a power of 2 and at least 4kB.
Cache should normally be disabled unless you change the setting in the corresponding MAR register.

Please note that the XMC MPAX unit will only enable the CorePac the use the mapped segments. For other masters like EDMA you also need to configure the MPAX unit of the MSMC (SMS and SES MPAX).

Ralf