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Re: place thread stack into CCM memory on STM32
- From: Oleg Uzenkov <o dot uzenkov at unicore dot co dot ua>
- To: eCos Discussion <ecos-discuss at sourceware dot org>
- Date: Fri, 17 Oct 2014 15:02:28 +0300
- Subject: Re: place thread stack into CCM memory on STM32
- Authentication-results: sourceware.org; auth=none
- References: <543FCF93 dot 4090209 at unicore dot co dot ua>
Hi Everyone,
STM32 controllers have CCM (Closely Coupled Memory) memory which acts
as RAM.
At present I do not use it. But I would like to.
I am developing eCos application in C++. I have something like this in
the header file:
class A :
{
public:
A ();
virtual ~A ();
..
protected:
cyg_thread _thread;
char _thread_stack [CYGNUM_HAL_STACK_SIZE_TYPICAL]
__attribute__((section(".ccm")));
...
As you can see, I want to place thread stack into CCM section (using
__attribute__((section("<name>"))).
But I do not know how to do it in a correct way. Please help! :-)
The Memory layout file I use has got:
..
SECTIONS
{
SECTIONS_BEGIN
USER_SECTION (ccm, ccm, 0x10000000, LMA_EQ_VMA)
..
And cortexm.ld file has got a macro for USER_SECTION:
#define USER_SECTION(_name_, _region_, _vma_, _lma_) \
._name_ _vma_ : _lma_ \
{ __ ## _name_ ## _start = ABSOLUTE (.); \
*(._name_*) \
__ ## _name_ ## _end = ABSOLUTE (.); } \
> _region_
When I compile the project I get an error:
error: section attribute not allowed for '_thread_stack'
Do I specify attribute in the correct place?
Ok, it appears that it is possible to specify
__attribute__((section("<name>"))) for class's member methods.
It can also be specified for file level or global level variables and
functions.
But unfortunately there is no directive to place the whole class into a
specific memory region.
As to working with STM32 I managed to place thread stacks into CCM
section (why waist it!) by declaring stack as a file level variable:
static char _thread_stack [CYGNUM_HAL_STACK_SIZE_TYPICAL]
CYGBLD_ATTRIB_SECTION(".ccm");
Make sure to specify (NOLOAD) for .ccm section in mlt_ file:
USER_SECTION (ccm, ccm, 0x10000000 (NOLOAD), LMA_EQ_VMA)
Otherwise the binary will be enormous.
Oleg
My be I cannot do it for class members but only for global variables?
I would appreciate any help on this.
Oleg
...
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