External SRAM problem

pefo77 wrote on Sunday, March 02, 2014:

Hello,

i have problem with running RTOS and external SRAM.

If i use only internal SRAM all works fine. When i configure external
SRAM (i can send my ld file) then program don’t work.
I use Atmel Studio 6.1, ASF 3.14.0 and freertos 7.3.0, gcc 4.7.3

[sram.ld]
/* Memory Spaces Definitions */
MEMORY
{
rom (rx) : ORIGIN = 0x00400000, LENGTH = 0x00100000
ram (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00020000
ram_ext (rwxa) : ORIGIN = 0x60000000, LENGTH = 0x00100000
}

/* The stack size used by the application. NOTE: you need to adjust according to your application. */
stack_size = DEFINED(stack_size) ? stack_size : 0x019000;
ram_end = ORIGIN(ram_ext) + LENGTH(ram_ext) - 4;

SECTIONS
{
.text :
{
// deleted lines
// same in SRAM config
} > rom

PROVIDE_HIDDEN (__exidx_start = .);
.ARM.exidx :
{
  *(.ARM.exidx* .gnu.linkonce.armexidx.*)
} > rom
PROVIDE_HIDDEN (__exidx_end = .);

. = ALIGN(4);
_etext = .;

/* stack section */
.stack (NOLOAD):
{
    . = ALIGN(8);
    _sstack = .;
    . = . + __stack_size__;
    . = ALIGN(8);
    _estack = .;
} > ram

/* free ram section (for dma buffers, etc) */
.free_ram ():
{
    . = ALIGN(4);
    _sfree_ram = .;
} > ram

.relocate : AT (_etext)
{
    . = ALIGN(4);
    _srelocate = .;
    *(.ramfunc .ramfunc.*);
    *(.data .data.*);
    . = ALIGN(4);
    _erelocate = .;
} > ram_ext

/* .bss section which is used for uninitialized data */
.bss (NOLOAD) :
{
    . = ALIGN(4);
    _sbss = . ;
    _szero = .;
    *(.bss .bss.*)
    *(COMMON)
    . = ALIGN(4);
    _ebss = . ;
    _ezero = .;
} > ram_ext

. = ALIGN(4);
_end = . ;

}

davedoors wrote on Sunday, March 02, 2014:

What does “not work” mean? You can’t program the chip, or main() is not called, or main() is called but the scheduler does not start, or the scheduler does start but context switches don’t happen, or one of many other possibilities?

pefo77 wrote on Sunday, March 02, 2014:

Hello,

scheduler start, but don’t run any task. When i move xHeap (heap4.c) to internal SRAM, tasks is working.

same behavior is described here: http://www.freertos.org/FreeRTOS_Support_Forum_Archive/May_2012/freertos_Put_heap_in_external_memory_for_STM32_5243508.html

Peter.

rtel wrote on Sunday, March 02, 2014:

Does the chip allow the stack to be allocated in external RAM?

If so, what happens if you allocate and use external SRAM before the
scheduler is started? For example:


void main( void )
{
char *c;
long l, lError = pdFALSE;

    /* Allocate a buffer. */
    c = pvPortMalloc( 1000 );

    /* Fill the buffer with known values. */
    for( l = 0; l < 1000; l++ )
    {
        c[ l ] = ( char ) l;
    }

    /* Check the value was actually written. */
    for( l = 0; l < 1000; l++ )
    {
        if( c[ l ] != ( char ) l )
        {
            lError = pdTRUE;
        }
    }
}

pefo77 wrote on Sunday, March 02, 2014:

Hi,

no error i make selft-test after initialization SRAM (2 passes),

sysclk_get_main_hz: 240000000
sysclk_get_cpu_hz: 120000000
sysclk_get_peripheral_hz: 120000000
SystemCoreClock: 120000000
SRAM sram_init_status_flag: 0
size of unsigned long: 4
size of double: 8
size of float: 4
size of int: 4
size of long: 4
size of ptrdiff_t: 4

lError: 0

If the xHeap is in ext SRAM , program hang up in HardFault_Handler - randomly (one or two task calls) - i think there is problem with timing SMC & EBI, and context switching. I have fully funcitonal program using ext. SRAM (without FreeRTOS).

Task: 1

Task: 2

Error: RTOS is down! <---- HardFault_Handler called here

Peter.

rtel wrote on Sunday, March 02, 2014:

If the xHeap is in ext SRAM , program hang up in HardFault_Handler -

I’m afraid I don’t know why that would be. It could be a timing issue.
If the crash happens in the context switch code then it might be that
some additional barrier instructions would fix it.

I have fully funcitonal program using ext. SRAM (without FreeRTOS).

Is that with the stack in SRAM too?

Regards.

pefo77 wrote on Sunday, March 02, 2014:

Memory map is same, stack + some dma buffers is in internal sram. Relocation sector + heap is in ext. Sram.

Peter.

davedoors wrote on Sunday, March 02, 2014:

stack + some dma buffers is in internal sram

The two cases are not the same then.

If you put the FreeRTOS heap in external RAM then the stacks used by the tasks will also be in external RAM.

pefo77 wrote on Sunday, March 02, 2014:

It’s true, because freertos have own stack in heap, but main stack is internal sram (see ld file). I must try to force freertos to use main stack in internal sram and heap in ext sram (for malloc and pvPortMalloc).

Peter

pefo77 wrote on Sunday, March 02, 2014:

Some dmb, dsb and isb helps, but not solve it (task’s is executed more times before hangs in HardFault), i going to try v8.0.0

pefo77 wrote on Sunday, March 02, 2014:

After many tests i solved some hanging issue, i use 50ns ext. SRAM, timing waves is set precisly to fit it (measured), SRAM woking well without erros, but if i start use FreeRTOS with heap mapped to ext. SRAM, programs hangs in HardFault_Handler. When i set the SMC_CYCLE_NWE_CYCLE, SMC_CYCLE_NRD_CYCLE two ticks longer, then stuff start working in FreeRTOS, maybe MATRIX arbitration settings helps too.

Peter.