Add defs for flexspi2

teensy4/avr/pgmspace.h

 #define FASTRUN __attribute__ ((section(".fastrun") ))
 #define PROGMEM __attribute__((section(".progmem")))
 #define FLASHMEM __attribute__((section(".flashmem")))
+#define EXTMEM __attribute__((section(".externalram")))
 
 #define PGM_P  const char *
 #define PSTR(str) ({static const char data[] PROGMEM = (str); &data[0];})

teensy4/imxrt.h

 #define CCM_CBCDR_IPG_PODF_MASK			((uint32_t)(0x03 << 8))
 #define CCM_CBCDR_SEMC_ALT_CLK_SEL		((uint32_t)(1<<7))
 #define CCM_CBCDR_SEMC_CLK_SEL			((uint32_t)(1<<6))
+#define CCM_CBCMR_FLEXSPI2_PODF(n)		((uint32_t)(((n) & 0x07) << 29))
 #define CCM_CBCMR_LPSPI_PODF(n)			((uint32_t)(((n) & 0x07) << 26))
 #define CCM_CBCMR_LCDIF_PODF(n)			((uint32_t)(((n) & 0x07) << 23))
 #define CCM_CBCMR_PRE_PERIPH_CLK_SEL(n)		((uint32_t)(((n) & 0x03) << 18))
 #define CCM_CBCMR_TRACE_CLK_SEL(n)		((uint32_t)(((n) & 0x03) << 14))
 #define CCM_CBCMR_PERIPH_CLK2_SEL(n)		((uint32_t)(((n) & 0x03) << 12))
-#define CCM_CBCMR_PERIPH_CLK2_SEL_MASK		((uint32_t)(0x03 << 12))
+#define CCM_CBCMR_FLEXSPI2_CLK_SEL(n)		((uint32_t)(((n) & 0x03) << 8))
 #define CCM_CBCMR_LPSPI_CLK_SEL(n)		((uint32_t)(((n) & 0x03) << 4))
+#define CCM_CBCMR_FLEXSPI2_PODF_MASK		((uint32_t)(0x07 << 29))
 #define CCM_CBCMR_LPSPI_PODF_MASK		((uint32_t)(0x07 << 26))
 #define CCM_CBCMR_LCDIF_PODF_MASK		((uint32_t)(0x07 << 23))
 #define CCM_CBCMR_PRE_PERIPH_CLK_SEL_MASK	((uint32_t)(0x03 << 18))
 #define CCM_CBCMR_TRACE_CLK_SEL_MASK		((uint32_t)(0x03 << 14))
+#define CCM_CBCMR_PERIPH_CLK2_SEL_MASK		((uint32_t)(0x03 << 12))
+#define CCM_CBCMR_FLEXSPI2_CLK_SEL_MASK		((uint32_t)(0x03 << 8))
 #define CCM_CBCMR_LPSPI_CLK_SEL_MASK		((uint32_t)(0x03 << 4))
 #define CCM_CSCMR1_FLEXSPI_CLK_SEL(n)		((uint32_t)(((n) & 0x03) << 29))
 #define CCM_CSCMR1_FLEXSPI_PODF(n)		((uint32_t)(((n) & 0x07) << 23))

teensy4/imxrt1062_t41.ld

 	ITCM (rwx):  ORIGIN = 0x00000000, LENGTH = 512K
 	DTCM (rwx):  ORIGIN = 0x20000000, LENGTH = 512K
 	RAM (rwx):   ORIGIN = 0x20200000, LENGTH = 512K
-	FLASH (rwx): ORIGIN = 0x60000000, LENGTH = 1984K
+	FLASH (rwx): ORIGIN = 0x60000000, LENGTH = 7936K
+	ERAM (rwx):  ORIGIN = 0x70000000, LENGTH = 8192K
 }
 
 ENTRY(ImageVectorTable)
 		. = ALIGN(16);
 	} > RAM
 
+	.bss.extram (NOLOAD) : {
+		*(.externalram)
+	} > ERAM
+
 	_stext = ADDR(.text.itcm);
 	_etext = ADDR(.text.itcm) + SIZEOF(.text.itcm);
 	_stextload = LOADADDR(.text.itcm);

teensy4/startup.c

 #define SIZE_16M	(SCB_MPU_RASR_SIZE(23) | SCB_MPU_RASR_ENABLE)
 #define SIZE_32M	(SCB_MPU_RASR_SIZE(24) | SCB_MPU_RASR_ENABLE)
 #define SIZE_64M	(SCB_MPU_RASR_SIZE(25) | SCB_MPU_RASR_ENABLE)
+#define SIZE_256M	(SCB_MPU_RASR_SIZE(26) | SCB_MPU_RASR_ENABLE)
 #define REGION(n)	(SCB_MPU_RBAR_REGION(n) | SCB_MPU_RBAR_VALID)
 
 FLASHMEM void configure_cache(void)
 	SCB_MPU_RBAR = 0x60000000 | REGION(5); // QSPI Flash
 	SCB_MPU_RASR = MEM_CACHE_WBWA | READONLY | SIZE_16M;
 
+	SCB_MPU_RBAR = 0x70000000 | REGION(6); // FlexSPI2
+	SCB_MPU_RASR = MEM_CACHE_WBWA | READONLY | SIZE_256M;
+
+	SCB_MPU_RBAR = 0x70000000 | REGION(7); // FlexSPI2
+	SCB_MPU_RASR = MEM_CACHE_WBWA | READWRITE | SIZE_16M;
+
 	// TODO: 32 byte sub-region at 0x00000000 with NOACCESS, to trap NULL pointer deref
 	// TODO: protect access to power supply config
 	// TODO: 32 byte sub-region at end of .bss section with NOACCESS, to trap stack overflow