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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
  • +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

Reply
  • +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

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