Memory Overview¶

The following describes the default memory layout for the MitySOM-AM57x platform.

Useful links:
https://software-dl.ti.com/processor-sdk-rtos/esd/docs/latest/rtos/index_how_to_guides.html#customizing-memory-map-for-creating-multicore-applications-on-am57xx-using-ipc
https://www.ti.com/lit/an/sprac60/sprac60.pdf

DDR Memory¶

The AM57x has two EMIF banks, each connected to 1GB of DDR.

Memory Interface	Physical Address
EMIF 1	0x80000000
EMIF 2	0xC0000000

The DDR is mapped in the am57xx-mitysom.dtsi device tree which maps the 2GB of memory contiguously.

memory@0 {
     device_type = "memory";
     reg = <0x0 0x80000000 0x0 0x80000000>;
     };

Multi-Core Memory Map¶

The two DSP cores and two IPU cores are mapped in the am57xx-mitysom-baseboard.dtsi device tree.
This can be modified for example to remove the IPUs and increase the DSPs memory ranges. The resource table
maps the virtual addressing for the processor to the physical address of the CMA regions at load time via the
remoteproc Linux driver. See Customizing Multicore Applications for more details on adjusting the memory sizes.

ipu2_memory_region: ipu2-memory@95800000 {
     compatible = "shared-dma-pool";
     reg = <0x0 0x95800000 0x0 0x3800000>;
     reusable;
     status = "okay";
     };

dsp1_memory_region: dsp1-memory@99000000 {
     compatible = "shared-dma-pool";
     reg = <0x0 0x99000000 0x0 0x4000000>;
     reusable;
     status = "okay";
     };

 ipu1_memory_region: ipu1-memory@9d000000 {
     compatible = "shared-dma-pool";
     reg = <0x0 0x9d000000 0x0 0x2000000>;
     reusable;
     status = "okay";
     };

dsp2_memory_region: dsp2-memory@9f000000 {
     compatible = "shared-dma-pool";
     reg = <0x0 0x9f000000 0x0 0x800000>;
     reusable;
     status = "okay";
     };

DSP Virtual Memory Map¶

The DSP virtual memory maps are defined in rsc_table_vayu_dsp.h header that is part of the RTOS SDK. The default mapping is as follows:

Section	Virtual Address	Size
DSP_MEM_TEXT	0x95000000	0x00100000
DSP_MEM_DATA	0x95100000	0x00100000
DSP_MEM_HEAP	0x95200000	0x00300000

To setup a custom resource table, please refer to Customizing Multicore Applications as well as IPC Resource customTable
The resource table maps the virtual addressing for the processor to the physical address of the CMA regions at load time via the
remoteproc Linux driver.

This can be seen in the default config.bld DSP file.

/*  --- External Memory ---
 *  Virtual     Physical        Size            Comment
 *  ------------------------------------------------------------------------
 *  9500_0000   ????_????    10_0000  (  ~1 MB) EXT_CODE
 *  9510_0000   ????_????    10_0000  (   1 MB) EXT_DATA
 *  9520_0000   ????_????    30_0000  (   3 MB) EXT_HEAP
 *  9F00_0000   9F00_0000     6_0000  ( 384 kB) TRACE_BUF
 *  9F06_0000   9F06_0000     1_0000  (  64 kB) EXC_DATA
 *  9F07_0000   9F07_0000     7_0000  ( 448 kB) PM_DATA (Power mgmt)
 */
var evmDRA7XX_ExtMemMapDsp = {
    EXT_CODE: {
        name: "EXT_CODE",
        base: 0x95000000,
        len:  0x00100000,
        space: "code",
        access: "RWX" 
    },
    EXT_DATA: {
        name: "EXT_DATA",
        base: 0x95100000,
        len:  0x00100000,
        space: "data",
        access: "RW" 
    },
    EXT_HEAP: {
        name: "EXT_HEAP",
        base: 0x95200000,
        len:  0x00300000,
        space: "data",
        access: "RW" 
    },
    TRACE_BUF: {
        name: "TRACE_BUF",
        base: 0x9F000000,
        len:  0x00060000,
        space: "data",
        access: "RW" 
    },
    EXC_DATA: {
        name: "EXC_DATA",
        base: 0x9F060000,
        len:  0x00010000,
        space: "data",
        access: "RW" 
    },
    PM_DATA: {
        name: "PM_DATA",
        base: 0x9F070000,
        len:  0x00070000,
        space: "data",
        access: "RWX"  /* should this have execute perm? */
    },
};

DSP Stack/Heap Allocation¶

The default DSP configuration allocates 1MB for the Stack and 3MB for the Heap. You can change how much of this is used in the Dsp.cfg file as follows:

// Allocates the stack to be 4KB
Program.stack = 0x1000;

var Memory = xdc.useModule('xdc.runtime.Memory');
var HeapMem = xdc.useModule('ti.sysbios.heaps.HeapMem');
var heapMemParams = new HeapMem.Params();
// Allocates the heap to be 32KB
heapMemParams.size = 0x8000;
Memory.defaultHeapInstance = HeapMem.create(heapMemParams);