i.MX RT Crossover MCUs中的主题 Re: Getting initialized variables into HyperRAM

Getting initialized variables into HyperRAM

derekkrouze — Mon, 22 Aug 2022 21:37:13 GMT

Hello,

I've recently gotten HyperRAM working with the i.mx rt 1064. However, now I'm trying to place data in it for use with the application. I'm using a variation of the MIMXRT1064xxxxx_flexspi_nor.ld provided with the NXP sdk. I am currently not using MCUXpresso, but gcc and vscode implementation.

I added the memory region to the .ld file

MEMORY { m_flash_config (RX) : ORIGIN = 0x70000000, LENGTH = 0x00001000 m_ivt (RX) : ORIGIN = 0x70001000, LENGTH = 0x00001000 m_interrupts (RX) : ORIGIN = 0x70002000, LENGTH = 0x00000400 m_text (RX) : ORIGIN = 0x70002400, LENGTH = 0x003FDC00 m_data (RW) : ORIGIN = 0x20000000, LENGTH = 0x00020000 m_data2 (RW) : ORIGIN = 0x20200000, LENGTH = 0x00080000 m_hyperram (RWX) : ORIGIN = 0x60000000, LENGTH = 0x00020000 }

and a basic way to move data into the custom section:

.data_hyperram : { FILL(0xff) . = ALIGN(4) ; __start_data_hyperram = .; KEEP(*(m_hyperram_data)) . = ALIGN(4) ; __end_data_hyperram = .; } > m_hyperram

In my application I then have a macro to place variables there:

#define HYPERRAM_SECTION_DATA(func) __attribute__((section("m_hyperram_data"))) func HYPERRAM_SECTION_DATA(volatile uint32_t testdata = 0x12345678);

My variables seem to be correctly placed into the HyperRAM section, but they are not initialized. I am unsure if there is more I need to add to my .ld file, or if there are custom copy routines that I need to add to the startup.s file. Any help on where to go from here would be greatly appreciated.

Re: Getting initialized variables into HyperRAM

Hui_Ma — Wed, 24 Aug 2022 08:57:30 GMT

Hi,

It needs related routine/code to do the vaiable initialization at HyperRAM.

The MCUXpresso provides related code to do the variable initialization, while I am not sure gcc and vscode implementation provide the same function or not.

You need to add related code at <startup.s> file to do related variable initialization.

Thanks for the attention.

Mike

Re: Getting initialized variables into HyperRAM

derekkrouze — Thu, 25 Aug 2022 13:40:33 GMT

Thanks Mike,

I played around with this for a little bit and came up with a solution. Figured I'd post that for the next person who runs into this. The main missing piece was telling the linker where to place the data section. A section needed to be carved out below the .data section and the AT() keyword needed to be used:

__HYPERRAM_DATA_ROM = __HYPERFLASH_DATA_ROM + (__end_data_hyperflash - __start_data_hyperflash); /* HyperRam section*/ .data_hyperram : AT(__HYPERRAM_DATA_ROM) { FILL(0xff) . = ALIGN(4) ; __start_data_hyperram = .; KEEP(*(m_hyperram_data)) . = ALIGN(4) ; . = ALIGN(32); __ram_function_start__ = .; KEEP(*(m_hyperram_code)) . = ALIGN(128); __ram_function_end__ = .; __end_data_hyperram = .; } > m_hyperram

Then I found two different ways to copy the initialized values into RAM, one through modifying the startup assembly code, or you can do this with C in the startup routine.

ASM:

#ifdef __STARTUP_INITIALIZE_RAMFUNCTION ldr r2, =__ram_function_start__ ldr r3, =__ram_function_end__ #ifdef __PERFORMANCE_IMPLEMENTATION /* Here are two copies of loop implementations. First one favors performance * and the second one favors code size. Default uses the second one. * Define macro "__PERFORMANCE_IMPLEMENTATION" in project to use the first one */ subs r3, r2 ble .LC_ramfunc_copy_end .LC_ramfunc_copy_start: subs r3, #4 ldr r0, [r1, r3] str r0, [r2, r3] bgt .LC_ramfunc_copy_start .LC_ramfunc_copy_end: #else /* code size implemenation */ .LC_ramfunc_copy_start: cmp r2, r3 ittt lt ldrlt r0, [r1], #4 strlt r0, [r2], #4 blt .LC_ramfunc_copy_start #endif #endif /* __STARTUP_INITIALIZE_RAMFUNCTION */

extern unsigned int __start_data_hyperflash; extern unsigned int __end_data_hyperflash; extern unsigned int __HYPERFLASH_DATA_ROM; void copy_hyperram_data() { #ifndef __HYPERFLASH_ASM_ROM_COPY unsigned int* hyperflash_rom_table = &__HYPERFLASH_DATA_ROM; unsigned int* hyperflash_ram_table = &__start_data_hyperflash; unsigned int hyperflash_copy_size = (&__end_data_hyperflash - &__start_data_hyperflash); for (unsigned int Index = 0; Index < hyperflash_copy_size; Index++) { hyperflash_ram_table[Index] = hyperflash_rom_table[Index]; } #endif //__HYPERRAM_ASM_ROM_COPY }

Granted this is for my specific use case, but I'd imagine other linker files would follow the same procedure.

-Derek