mimxrt/bootloader: Add support for a UF2 bootlaoder.

Allowing to use e.g. the Adafruit bootloaders with MicroPython.
The .uf2 file is created in addition to the .bin and .hex files
allowing to use the latter ones without the bootloader for
debugging and testing.
The bootloader has to be installed as a preparation step using the
board specific methods, but then the firmware's .uf2 file version
can be installed using the bootloader. The bootloader can be invoked
with:

- double reset
- calling machine.bootloader()
- Using the touch1200 method

Loader scripts adapted for MIMXRT1011 and MIMXRT1021.

Signed-off-by: robert-hh <robert@hammelrath.com>

ports/mimxrt/Makefile

@@ -161,6 +161,14 @@ SRC_HAL_IMX_C += \
 	$(MCU_DIR)/drivers/fsl_romapi.c
 endif
 
+# If not empty, then it is 10xx.
+ifneq ($(findstring MIMXRT10, $(MCU_SERIES)),)
+BOOTLOADER_SIZE := 0x6000C000
+else
+CFLAGS += -DIMXRT11XX=1 -DIMXRT10XX=0
+BOOTLOADER_SIZE := 0x3000C000
+endif
+
 ifeq ($(MCU_SERIES), MIMXRT1176)
 INC += -I$(TOP)/$(MCU_DIR)/drivers/cm7
 
@@ -467,7 +475,7 @@ $(BUILD)/lib/tinyusb/src/device/usbd.o: CFLAGS += -Wno-missing-braces
 # Build targets
 # =============================================================================
 
-all: $(BUILD)/firmware.hex $(BUILD)/firmware.bin
+all: $(BUILD)/firmware.hex $(BUILD)/firmware.bin $(BUILD)/firmware.uf2
 
 # Process linker scripts with C preprocessor to exchange LDDEFINES and
 #	aggregate output of preprocessor in a single linker script `link.ld`
@@ -484,6 +492,11 @@ $(BUILD)/firmware.bin: $(BUILD)/firmware.elf
 $(BUILD)/firmware.hex: $(BUILD)/firmware.elf
 	$(Q)$(OBJCOPY) -O ihex -R .eeprom $< $@
 
+$(BUILD)/firmware.uf2: $(BUILD)/firmware.elf
+	$(Q)$(OBJCOPY) -O binary -R .stack -R .dtcm_bss -R .ivt -R .flash_config $^ $@-binpart
+	$(Q)$(PYTHON) $(TOP)/tools/uf2conv.py -b $(BOOTLOADER_SIZE) -f MIMXRT10XX -c -o $@ $@-binpart
+	$(Q)rm $@-binpart
+
 # Making OBJ use an order-only dependency on the generated pins.h file
 # has the side effect of making the pins.h file before we actually compile
 # any of the objects. The normal dependency generation will deal with the

ports/mimxrt/boards/MIMXRT1011.ld

@@ -14,9 +14,9 @@ flash_config_start  = flash_start + 0x00000400;
 flash_config_size   = 0x00000C00;
 ivt_start           = flash_start + 0x00001000;
 ivt_size            = 0x00001000;
-interrupts_start    = flash_start + 0x00002000;
+interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
-text_start          = flash_start + 0x00002400;
+text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
 text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));

ports/mimxrt/boards/MIMXRT1021.ld

@@ -14,9 +14,9 @@ flash_config_start  = flash_start;
 flash_config_size   = 0x00001000;
 ivt_start           = flash_start + 0x00001000;
 ivt_size            = 0x00001000;
-interrupts_start    = flash_start + 0x00002000;
+interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
-text_start          = flash_start + 0x00002400;
+text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
 text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));

ports/mimxrt/boards/common.ld

@@ -42,7 +42,8 @@ MEMORY
   m_vfs          (RX) : ORIGIN = vfs_start,             LENGTH = vfs_size
   /* Teensy uses the last bit of flash for recovery. */
   m_reserved     (RX) : ORIGIN = (vfs_start + vfs_size), LENGTH = reserved_size
-  m_itcm         (RX) : ORIGIN = itcm_start,            LENGTH = itcm_size
+  m_isr          (RX) : ORIGIN = itcm_start,            LENGTH = 0x400
+  m_itcm         (RX) : ORIGIN = itcm_start + 0x400,    LENGTH = itcm_size - 0x400
   m_dtcm         (RW) : ORIGIN = dtcm_start,            LENGTH = dtcm_size
   m_ocrm         (RW) : ORIGIN = ocrm_start,            LENGTH = ocrm_size
 
@@ -80,7 +81,8 @@ SECTIONS
     . = ALIGN(4);
   } > m_ivt
 
-  /* The startup code goes first into internal RAM */
+  /* ISR Vector table in flash. Copied to ITCM by ResetHandler(). */
+
   .interrupts :
   {
     __Vectors = .;
@@ -90,10 +92,9 @@ SECTIONS
     . = ALIGN(4);
   } > m_interrupts
 
-  __VECTOR_RAM = __Vectors;
-  __RAM_VECTOR_TABLE_SIZE_BYTES = 0x0;
+  __Vectors_RAM = itcm_start;
 
-  /* The program code and other data goes into internal RAM */
+  /* Some program code and other data goes into internal RAM */
   .text :
   {
     . = ALIGN(4);

ports/mimxrt/hal/resethandler_MIMXRT10xx.S

@@ -64,6 +64,19 @@ Reset_Handler:
  *      __ram_function_start__/__ram_function_end__ : ramfunction region
  *      copied to. Both must be aligned to 4 bytes boundary.  */
 
+/* Copy the ISR Vector table to the start of ITCM to be available when the
+   .uf2 bootlaoder is used */
+
+    ldr    r1, = __Vectors
+    ldr    r2, = __Vectors_RAM
+    movs   r3, 1024
+
+.LC_ISR:
+    subs    r3, #4
+    ldr    r0, [r1, r3]
+    str    r0, [r2, r3]
+    bgt    .LC_ISR
+
     ldr    r1, =__etext
     ldr    r2, =__data_start__
     ldr    r3, =__data_end__

ports/mimxrt/modmachine.c

@@ -76,6 +76,11 @@ typedef enum {
     MP_SOFT_RESET
 } reset_reason_t;
 
+// Copied from inc/uf2.h in https://github.com/Microsoft/uf2-samd21
+#define DBL_TAP_REG   SNVS->LPGPR[3]
+#define DBL_TAP_MAGIC 0xf01669ef // Randomly selected, adjusted to have first and last bit set
+#define DBL_TAP_MAGIC_QUICK_BOOT 0xf02669ef
+
 static mp_obj_t mp_machine_unique_id(void) {
     unsigned char id[8];
     mp_hal_get_unique_id(id);
@@ -154,6 +159,10 @@ NORETURN static void mp_machine_deepsleep(size_t n_args, const mp_obj_t *args) {
     }
 }
 
+// static bool uf2_bootloader_available(void) {
+//     return SNVS->LPGPR[0] != 0;
+// }
+
 NORETURN void mp_machine_bootloader(size_t n_args, const mp_obj_t *args) {
     #if defined(MICROPY_BOARD_ENTER_BOOTLOADER)
     // If a board has a custom bootloader, call it first.
@@ -163,7 +172,11 @@ NORETURN void mp_machine_bootloader(size_t n_args, const mp_obj_t *args) {
     uint32_t arg = 0xEB110000;
     ROM_RunBootloader(&arg);
     #else
-    // No custom bootloader, or run bootloader API, then just reset.
+    // No custom bootloader, or run bootloader API, the set
+    // the flag for the UF2 bootloader
+    // Pretend to be the first of the two reset presses needed to enter the
+    // bootloader. That way one reset will end in the bootloader.
+    DBL_TAP_REG = DBL_TAP_MAGIC;
     WDOG_TriggerSystemSoftwareReset(WDOG1);
     #endif
     while (1) {

ports/mimxrt/mpconfigport.h

@@ -116,6 +116,7 @@ uint32_t trng_random_u32(void);
 #define MICROPY_PY_MACHINE_UART_SENDBREAK   (1)
 #define MICROPY_PY_MACHINE_UART_IRQ         (1)
 #define MICROPY_PY_ONEWIRE                  (1)
+#define MICROPY_PY_MACHINE_BOOTLOADER       (1)
 
 // fatfs configuration used in ffconf.h
 #define MICROPY_FATFS_ENABLE_LFN            (1)
@@ -150,6 +151,7 @@ uint32_t trng_random_u32(void);
 
 #define MICROPY_HW_ENABLE_USBDEV            (1)
 #define MICROPY_HW_USB_CDC                  (1)
+#define MICROPY_HW_USB_CDC_1200BPS_TOUCH    (1)
 
 // Hooks to add builtins