mimxrt: Add support for VfsRom filesystem.

robert-hh · dpgeorge · commit b857a9131e5c · 2026-01-02T14:48:16.000+11:00
The default size for the ROM partition is 256k, and it is placed in flash
between the text and writable vfs sections.  Its size can be changed in
`mpconfigboard.mk` by defining `MICROPY_HW_ROMFS_BYTES` to a different
value, but it must not be smaller than a single sector.

The MIMXRT1170_EVK and SEEED ARCH MIX ROMFS boards use a larger size of
512kB.  ROMFS support is disabled for MIMXRT1050_EVKB due to issues with
Hyperflash.

The extents of the ROM partition are defined by the linker-level symbols
`_micropy_hw_romfs_part0_start` and `_micropy_hw_romfs_part0_size`,
following existing ports.

Signed-off-by: Damien George &lt;damien@micropython.org&gt;
Signed-off-by: robert-hh &lt;robert@hammelrath.com&gt;
diff --git a/ports/mimxrt/Makefile b/ports/mimxrt/Makefile
@@ -311,6 +311,11 @@ ifeq ($(USE_UF2_BOOTLOADER),1)
 	CFLAGS += -DMICROPY_MACHINE_UF2_BOOTLOADER=1
 endif
 
+# Set the default size of the VfsRom file system. Can be changed at board level
+ifeq ($(MICROPY_HW_ROMFS_BYTES),)
+	MICROPY_HW_ROMFS_BYTES ?= 0x40000
+endif
+
 # Add sources for respective board flash type
 # Add hal/flexspi_nor_flash.c or hal/flashspi_hyper_flash.c respectively
 SRC_HAL_C += hal/flexspi_$(subst qspi_,,$(FLEXSPI_FLASH_TYPE)).c
@@ -494,9 +499,10 @@ LDFLAGS += \
 # LDDEFINES are used for link time adaptation of linker scripts, utilizing
 #	the C preprocessor. Therefore keep LDDEFINES separated from LDFLAGS!
 
-LDDEFINES = \
+LDDEFINES += \
 	-DMICROPY_HW_FLASH_BASE=$(MICROPY_HW_FLASH_BASE) \
-	-DMICROPY_HW_FLASH_SIZE=$(MICROPY_HW_FLASH_SIZE)
+	-DMICROPY_HW_FLASH_SIZE=$(MICROPY_HW_FLASH_SIZE) \
+	-DMICROPY_HW_ROMFS_BYTES=$(MICROPY_HW_ROMFS_BYTES)
 
 ifdef MICROPY_HW_FLASH_RESERVED
 LDDEFINES += -DMICROPY_HW_FLASH_RESERVED=$(MICROPY_HW_FLASH_RESERVED)
diff --git a/ports/mimxrt/boards/MIMXRT1011.ld b/ports/mimxrt/boards/MIMXRT1011.ld
@@ -18,8 +18,10 @@ interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
 text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00008000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/MIMXRT1015.ld b/ports/mimxrt/boards/MIMXRT1015.ld
@@ -18,8 +18,10 @@ interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
 text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00008000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/MIMXRT1021.ld b/ports/mimxrt/boards/MIMXRT1021.ld
@@ -18,8 +18,10 @@ interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
 text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00010000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/MIMXRT1050_EVK/mpconfigboard.mk b/ports/mimxrt/boards/MIMXRT1050_EVK/mpconfigboard.mk
@@ -10,6 +10,7 @@ MICROPY_HW_SDRAM_SIZE  = 0x2000000  # 32MB
 MICROPY_HW_FLASH_CLK = kFlexSpiSerialClk_133MHz
 MICROPY_HW_FLASH_QE_CMD = 0x01
 MICROPY_HW_FLASH_QE_ARG = 0x40
+MICROPY_HW_ROMFS_BYTES = 0  # Disabled for a board with Hyperflash
 
 MICROPY_PY_LWIP = 1
 MICROPY_PY_SSL = 1
diff --git a/ports/mimxrt/boards/MIMXRT1052.ld b/ports/mimxrt/boards/MIMXRT1052.ld
@@ -20,8 +20,10 @@ interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
 text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00200000;
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00020000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/MIMXRT1062.ld b/ports/mimxrt/boards/MIMXRT1062.ld
@@ -20,8 +20,10 @@ interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
 text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00020000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/MIMXRT1064.ld b/ports/mimxrt/boards/MIMXRT1064.ld
@@ -14,8 +14,10 @@ interrupts_start    = flash_start + 0x0000C000;
 interrupts_size     = 0x00000400;
 text_start          = flash_start + 0x0000C400;
 vfs_start           = flash_start + 0x00100000;
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00020000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/MIMXRT1170_EVK/mpconfigboard.mk b/ports/mimxrt/boards/MIMXRT1170_EVK/mpconfigboard.mk
@@ -9,6 +9,7 @@ MICROPY_HW_FLASH_RESERVED ?= 0x100000  # 1MB CM4 Code address space
 MICROPY_HW_FLASH_CLK = kFlexSpiSerialClk_133MHz
 MICROPY_HW_FLASH_QE_CMD = 0x31
 MICROPY_HW_FLASH_QE_ARG = 0x02
+MICROPY_HW_ROMFS_BYTES = 0x80000  # 512kB
 
 MICROPY_HW_SDRAM_AVAIL = 1
 MICROPY_HW_SDRAM_SIZE  = 0x4000000  # 64MB
diff --git a/ports/mimxrt/boards/MIMXRT1176.ld b/ports/mimxrt/boards/MIMXRT1176.ld
@@ -30,8 +30,10 @@ m_core1_image_start = vfs_start - 0x00040000;
 m_core1_image_size  = 0x00040000;
 #endif
 
-text_size           = ((vfs_start) - (text_start));
 vfs_size            = ((flash_end) - (vfs_start));
+_micropy_hw_romfs_part0_start = ((vfs_start) - MICROPY_HW_ROMFS_BYTES);
+_micropy_hw_romfs_part0_size = MICROPY_HW_ROMFS_BYTES;
+text_size           = ((_micropy_hw_romfs_part0_start) - (text_start));
 itcm_start          = 0x00000000;
 itcm_size           = 0x00020000;
 dtcm_start          = 0x20000000;
diff --git a/ports/mimxrt/boards/SEEED_ARCH_MIX/mpconfigboard.mk b/ports/mimxrt/boards/SEEED_ARCH_MIX/mpconfigboard.mk
@@ -7,6 +7,7 @@ MICROPY_HW_FLASH_SIZE = 0x800000  # 8MB
 MICROPY_HW_FLASH_CLK = kFlexSpiSerialClk_133MHz
 MICROPY_HW_FLASH_QE_CMD = 0x01
 MICROPY_HW_FLASH_QE_ARG = 0x40
+MICROPY_HW_ROMFS_BYTES = 0x80000  # 512kB
 
 MICROPY_HW_SDRAM_AVAIL = 1
 MICROPY_HW_SDRAM_SIZE  = 0x2000000  # 32MB
diff --git a/ports/mimxrt/mimxrt_flash.c b/ports/mimxrt/mimxrt_flash.c
@@ -5,6 +5,7 @@
  *
  * Copyright (c) 2020-2021 Damien P. George
  * Copyright (c) 2021-2023 Philipp Ebensberger
+ * Copyright (c) 2021-2024 Robert Hammelrath
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -29,6 +30,7 @@
 
 #include "py/runtime.h"
 #include "extmod/vfs.h"
+#include "py/mperrno.h"
 #include "modmimxrt.h"
 #include "flash.h"
 #include BOARD_FLASH_OPS_HEADER_H
@@ -60,6 +62,19 @@ static mp_obj_t mimxrt_flash_make_new(const mp_obj_type_t *type, size_t n_args,
     return MP_OBJ_FROM_PTR(&mimxrt_flash_obj);
 }
 
+static mp_int_t mimxrt_flash_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
+    mimxrt_flash_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    if (flags == MP_BUFFER_READ) {
+        bufinfo->buf = (void *)((uintptr_t)&__flash_start + self->flash_base);
+        bufinfo->len = self->flash_size;
+        bufinfo->typecode = 'B';
+        return 0;
+    } else {
+        // Write unsupported.
+        return 1;
+    }
+}
+
 // readblocks(block_num, buf, [offset])
 // read size of buffer number of bytes from block (with offset) into buffer
 static mp_obj_t mimxrt_flash_readblocks(size_t n_args, const mp_obj_t *args) {
@@ -151,5 +166,39 @@ MP_DEFINE_CONST_OBJ_TYPE(
     MP_QSTR_Flash,
     MP_TYPE_FLAG_NONE,
     make_new, mimxrt_flash_make_new,
+    buffer, mimxrt_flash_get_buffer,
     locals_dict, &mimxrt_flash_locals_dict
     );
+
+#if MICROPY_VFS_ROM
+
+extern uint8_t _micropy_hw_romfs_part0_start;
+extern uint8_t _micropy_hw_romfs_part0_size;
+
+// Put VfsRom file system between the code space and the VFS file system.
+// The size is defined in Makefile(s) as linker symbol MICROPY_HW_ROMFS_BYTES.
+// For machine.mem32 the absolute address is required, for the flash functions
+// erase and write the offset to the flash start address.
+#define MICROPY_HW_ROMFS_BASE ((uintptr_t)&_micropy_hw_romfs_part0_start - (uintptr_t)&__flash_start)
+#define MICROPY_HW_ROMFS_BYTES ((uintptr_t)&_micropy_hw_romfs_part0_size)
+
+static mimxrt_flash_obj_t mimxrt_flash_romfs_obj = {
+    .base = { &mimxrt_flash_type },
+};
+
+mp_obj_t mp_vfs_rom_ioctl(size_t n_args, const mp_obj_t *args) {
+    if (MICROPY_HW_ROMFS_BYTES <= 0) {
+        return MP_OBJ_NEW_SMALL_INT(-MP_EINVAL);
+    }
+    switch (mp_obj_get_int(args[0])) {
+        case MP_VFS_ROM_IOCTL_GET_NUMBER_OF_SEGMENTS:
+            return MP_OBJ_NEW_SMALL_INT(1);
+        case MP_VFS_ROM_IOCTL_GET_SEGMENT:
+            mimxrt_flash_romfs_obj.flash_base = MICROPY_HW_ROMFS_BASE;
+            mimxrt_flash_romfs_obj.flash_size = MICROPY_HW_ROMFS_BYTES;
+            return MP_OBJ_FROM_PTR(&mimxrt_flash_romfs_obj);
+        default:
+            return MP_OBJ_NEW_SMALL_INT(-MP_EINVAL);
+    }
+}
+#endif  // MICROPY_VFS_ROM
diff --git a/ports/mimxrt/mpconfigport.h b/ports/mimxrt/mpconfigport.h
@@ -60,6 +60,9 @@ uint32_t trng_random_u32(void);
 #define MICROPY_SCHEDULER_DEPTH             (8)
 #define MICROPY_SCHEDULER_STATIC_NODES      (1)
 #define MICROPY_VFS                         (1)
+#ifndef MICROPY_VFS_ROM
+#define MICROPY_VFS_ROM                     (1)
+#endif
 
 // Control over Python builtins
 #define MICROPY_PY_BUILTINS_HELP_TEXT       mimxrt_help_text
