Dynamically partition ITCM & DTCM on IMXRT1062

teensy4/bootdata.c

 
 __attribute__ ((section(".vectors"), used))
 const uint32_t vector_table[2] = {
+#if defined(__IMXRT1052__)
 	(uint32_t)&_estack,
+#elif defined(__IMXRT1062__)
+	0x20010000, // 64K DTCM for boot, ResetHandler configures stack after ITCM/DTCM setup
+#endif
 	(uint32_t)&ResetHandler
 };
 

teensy4/imxrt1062.ld

 MEMORY
 {
-	ITCM (rwx):  ORIGIN = 0x00000000, LENGTH = 128K
-	DTCM (rwx):  ORIGIN = 0x20000000, LENGTH = 128K
-	RAM (rwx):   ORIGIN = 0x20200000, LENGTH = 256K
+	ITCM (rwx):  ORIGIN = 0x00000000, LENGTH = 512K
+	DTCM (rwx):  ORIGIN = 0x20000000, LENGTH = 512K
+	RAM (rwx):   ORIGIN = 0x20200000, LENGTH = 512K
 	FLASH (rwx): ORIGIN = 0x60000000, LENGTH = 1536K
 }
 
 	_edata = ADDR(.data) + SIZEOF(.data);
 	_sdataload = LOADADDR(.data);
 
-	_estack = ORIGIN(DTCM) + LENGTH(DTCM);
-
 	_sbss = ADDR(.bss);
 	_ebss = ADDR(.bss) + SIZEOF(.bss);
 
 	_heap_start = ADDR(.bss.dma) + SIZEOF(.bss.dma);
 	_heap_end = ORIGIN(RAM) + LENGTH(RAM);
 
+	_itcm_block_count = (SIZEOF(.text) + 0x7FFE) >> 15;
+	_flexram_bank_config = 0xAAAAAAAA | ((1 << (_itcm_block_count * 2)) - 1);
+	_estack = ORIGIN(DTCM) + ((16 - _itcm_block_count) << 15);
+
 	_flashimagelen = SIZEOF(.text.progmem) + SIZEOF(.text) + SIZEOF(.data);
 	_teensy_model_identifier = 0x24;
 

teensy4/startup.c

 extern unsigned long _edata;
 extern unsigned long _sbss;
 extern unsigned long _ebss;
-
+extern unsigned long _flexram_bank_config;
+extern unsigned long _estack;
 
 __attribute__ ((used, aligned(1024)))
 void (* _VectorsRam[NVIC_NUM_INTERRUPTS+16])(void);
 extern void __libc_init_array(void); // C++ standard library
 
 
-__attribute__((section(".startup"), optimize("no-tree-loop-distribute-patterns")))
+__attribute__((section(".startup"), optimize("no-tree-loop-distribute-patterns"), naked))
 void ResetHandler(void)
 {
 	unsigned int i;
 
-	//force the stack to begin at some arbitrary location
-	//__asm__ volatile("mov sp, %0" : : "r" (0x20010000) : );
-
+#if defined(__IMXRT1062__)
+	IOMUXC_GPR_GPR17 = (uint32_t)&_flexram_bank_config;
+	IOMUXC_GPR_GPR16 = 0x00000007;
+	IOMUXC_GPR_GPR14 = 0x00AA0000;
+	__asm__ volatile("mov sp, %0" : : "r" ((uint32_t)&_estack) : );
+#endif
 	// pin 13 - if startup crashes, use this to turn on the LED early for troubleshooting
 	//IOMUXC_SW_MUX_CTL_PAD_GPIO_B0_03 = 5;
 	//IOMUXC_SW_PAD_CTL_PAD_GPIO_B0_03 = IOMUXC_PAD_DSE(7);
-	//GPIO2_GDIR |= (1<<3);
-	//GPIO2_DR_SET = (1<<3); // digitalWrite(13, HIGH);
+	//IOMUXC_GPR_GPR27 = 0xFFFFFFFF;
+	//GPIO7_GDIR |= (1<<3);
+	//GPIO7_DR_SET = (1<<3); // digitalWrite(13, HIGH);
 
 	// Initialize memory
 	memory_copy(&_stext, &_stextload, &_etext);