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Memory allocation Issue

Mehran Gomeshlou

Hi all!
When we used malloc of size 2**15 in C code, it does not allocate.

uint16_t *out = (uint16_t *)malloc(samples_size * sizeof(uint16_t));
if (!out) {
fprintf(stderr, "Memory allocation for out failed.\n");
exit(1);
}
unsigned int samples_size       = 1 << 15;

DTCM 256kb and also ITCM in our chip (ARM Cortex M7) is 256kb.

CM7_DTCMCR
x 0xE000EF94
0xE000EF94: 0x00000049

CM7_ITCMCR
x 0xE000EF90
0xE000EF90: 0x00000049

It seems that I cannot use all 256kb that I have in DTCM.
Can you give me insights through this?

Based on ARM support, I have to located this (via scatterloading region ARM_LIB_(STACK)HEAP), but I do not know how to do it?
Appreciate your kind support and assistance.

Parents Reply Children
  • 0 in reply to Mehran Gomeshlou

    Hi again!

    I Went through the description and wrote this scatter file

    /* Define the entire 256 kB DTCM region */
    LR_DTCM 0x20000000 0x00040000 {

    /* Execution region for code and read-only data.
    Here we reserve 128 kB from 0x20000000 to 0x2001FFFF. */
    ER_DTCM 0x20000000 0x00020000 {
    *(InRoot$$Sections)
    *(.text*)
    *(.rodata*)
    *(.constdata*)
    *(.ARM.Collect*)
    *(+RO)
    }

    /* Execution region for read-write data.
    Here we reserve 32 kB from 0x20020000 to 0x20027FFF. */
    RW_DTCM 0x20020000 0x00008000 {
    *(.data*)
    *(.bss*)
    *(+RW)
    }

    /* Define the heap region for dynamic allocations.
    This reserve is 64 kB from 0x20028000 to 0x20037FFF. */
    ARM_LIB_HEAP 0x20028000 EMPTY 0x00010000 {
    /* Heap region: 64 kB available for malloc() */
    }

    /* Define the stack region.
    Here we reserve 32 kB from 0x20038000 to 0x2003FFFF. */
    ARM_LIB_STACK 0x20038000 EMPTY 0x00008000 {
    /* Stack region: 32 kB */
    }
    }

    Any suggestions if it is the right one to dedicate 64kB of 256kB from DTCM?

    Warm regards


  • +1 Arm Employee Badge in reply to Mehran Gomeshlou

    Hi again

    As a quick test, I added your scatter file above into the "startup_Cortex-M7_AC6" example.  With some tweaks, I was able to get the example basically working.

    Note that the default C library itself uses some heap space for things like printf, so your full "samples_size = 1 << 15" didn't quite fit in the heap space, but "samples_size = 1 << 14" did.

    I could see a malloc call executing & returning correctly, with "out" being 0x20028060, which looks correct.  
    That's 0x20028000 (your heap base) plus 0x60 bytes of C library private workspace.

    Stephen

  • 0 in reply to Stephen Theobald

    Thank you Stephen
    It was a great help!
    The issue is resolved.

  • 0 in reply to Mehran Gomeshlou

    Hi again!

    I have sort of a small question.
    I have created this scatter file in my C project in ARM DS.

    The question is when I go to my CMSIS project, can I use the same scatter file, or any changes and modifications should be made on that?

    And in my file, both stack and heap are created in DTCM. Shall I define ITCM statically in the same scatter file as well?

    regards

  • +1 Arm Employee Badge in reply to Mehran Gomeshlou

    CMSIS Packs typically provide referenc scatter files for the device used, but you can of course edit as appropriate, for example to locate the stack/heap in the DTCM rather than general memory.

  • 0 in reply to Ronan Synnott

    Hi

    Thank you Ronan and Stephen for providing me the insights, now I changed the scatter file in a way that my code can use the resources in an optimized way!

    Warm regards
    Mehran