bricks/ev3rt: Make bootable firmware.

ev3rt still expects a microSD card to work properly for the moment, but it no longer needs to contain the uImage.

Author: laurensvalk

bricks/ev3rt/Makefile

@@ -165,25 +165,30 @@ export EV3RT_BRICK_DIR
 export EV3RT_LIB_DIR
 export APPLDIRS
 
-all: ev3rt
+all: uImage firmware.bin
+
+#TODO: Build our own u-boot image. Use any official firmware for now. u-boot will be extracted from it.
+UBOOT_FILE = $(EV3RT_BRICK_DIR)/officialfw.bin
+
+firmware.bin: uImage
+	python $(EV3RT_BRICK_DIR)/make_bootable_image.py $(UBOOT_FILE) $(BUILD)/uImage $(BUILD)/firmware.bin
 
 ev3rt-config: $(EV3RT_BRICK_DIR) $(BUILD)/libkernel.a prepare-obj-folder
 	make -C $(BUILD) offset.h kernel_cfg.h
 
-ev3rt-main: $(OBJ)
+mkimage: $(OBJ)
 	make -C $(BUILD) > /dev/null && \
 	arm-none-eabi-objcopy -O binary $(BUILD)/$(KERNEL) $(BUILD)/$(KERNEL).bin
 	@mkimage -A arm -O linux -T kernel -C none -a 0xc0008000 -e 0xc0008000 \
         -n "TOPPERS/$(KERNEL) Kernel (EV3)" \
 		-d $(BUILD)/$(KERNEL).bin $(BUILD)/uImage
 	@chmod +x $(BUILD)/uImage
 
-ev3rt:
+uImage:
 	mkdir -p $(EV3RT_BRICK_DIR)/build
 	make $(BUILD)/pybricks.cfg
 	make ev3rt-config
-	make ev3rt-main
-
+	make mkimage
 $(BUILD)/libkernel.a: prepare-obj-folder
 	make -C $(BUILD) libkernel.a
 

bricks/ev3rt/make_bootable_image.py

@@ -0,0 +1,59 @@
+import argparse
+
+# Expected layout of the firmware image:
+#
+# u-boot.bin can be the first 256KiB from official firmware or a custom U-Boot.
+#
+# | Image (file)       | Start Addr. | Max. Size         | Notes
+# +--------------------+-------------+-------------------+----------
+# | u-boot.bin         |         0x0 |  0x40000 (256KiB) |
+# | da850-lego-ev3.dtb |     0x40000 |  0x10000 (64KiB)  | Not used.
+# | uImage             |     0x50000 | 0x400000 (4MiB)   | Smaller size is allowed.
+# | rootfs (squashfs)  |    0x450000 | 0xa00000 (10MiB)  | Not used.
+
+
+UBOOT_MAX_SIZE = 256 * 1024
+UIMAGE_MAX_SIZE = 4 * 1024 * 1024
+UIMAGE_OFFSET = 0x50000
+FIRMWARE_ROUND_SIZE = 256 * 1024
+
+
+def make_firmware(uboot_blob, uimage_blob):
+
+    if len(uboot_blob) > UBOOT_MAX_SIZE:
+        print("u-boot file is bigger than expected. Using only the first 256KiB.")
+        uboot_blob = uboot_blob[:UBOOT_MAX_SIZE]
+
+    if len(uimage_blob) > UIMAGE_MAX_SIZE:
+        raise ValueError("uImage file is too big.")
+
+    # Gets combined size, rounded to nearest expected size.
+    combined_size = UIMAGE_OFFSET + len(uimage_blob)
+    combined_size = (
+        (combined_size + FIRMWARE_ROUND_SIZE) // FIRMWARE_ROUND_SIZE * FIRMWARE_ROUND_SIZE
+    )
+
+    # Put it all together.
+    padding_uboot = b"\0" * (UIMAGE_OFFSET - len(uboot_blob))
+    padding_uimage = b"\0" * (combined_size - UIMAGE_OFFSET - len(uimage_blob))
+    return uboot_blob + padding_uboot + uimage_blob + padding_uimage
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description="Create a bootable EV3 firmware image from a u-boot and uImage file."
+    )
+    parser.add_argument(
+        "uboot",
+        help="The u-boot file, or an official firmware file from which to extract the u-boot.",
+    )
+    parser.add_argument("uimage", help="The uImage file")
+    parser.add_argument("output", help="The output file")
+    args = parser.parse_args()
+
+    with open(args.uboot, "rb") as uboot_file, open(args.uimage, "rb") as uimage_file, open(
+        args.output, "wb"
+    ) as output_file:
+        combined = make_firmware(uboot_file.read(), uimage_file.read())
+        output_file.write(combined)
+        print(f"Created {args.output} with size {len(combined) // 1024} KB.")