bricks/ev3: use .elf instead of uImage

Replace creating a uImage with using the .elf file directly for the EV3
firmware. This simplifies the build process and avoids the need for
u-boot-tools. U-Boot already knows how to load the .elf file, so we
can use it directly by using `bootelf` instead of `bootm` (this change
was made in the pybricks/v2.0.0 release of u-boot).

In order to keep the size of the .elf file small, we do not enable
`-ffunction-sections` and `-fdata-sections` for the EV3 firmware.
This avoids the large tables of section names that are generated by
these flags, which would otherwise increase the size of the .elf file
by nearly 200 kB. The .elf file is still a bit larger than the uImage
because of a bit more overhead, but only by less than 4kB.

Author: dlech

.github/workflows/build.yml

@@ -93,7 +93,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
     - name: Install cross-compiler
-      run: sudo apt-get update && sudo apt-get install --yes gcc-arm-none-eabi u-boot-tools
+      run: sudo apt-get update && sudo apt-get install --yes gcc-arm-none-eabi
     - name: Checkout repo
       uses: actions/checkout@v4
       with:

.github/workflows/release.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Install cross-compiler
-        run: sudo apt-get update && sudo apt-get install --yes gcc-arm-none-eabi u-boot-tools
+        run: sudo apt-get update && sudo apt-get install --yes gcc-arm-none-eabi
       - name: Checkout code
         uses: actions/checkout@v4
         with:

.github/workflows/stats.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Install cross-compiler
-        run: sudo apt-get update && sudo apt-get install --yes gcc-arm-none-eabi u-boot-tools
+        run: sudo apt-get update && sudo apt-get install --yes gcc-arm-none-eabi
       - name: Checkout code
         uses: actions/checkout@v4
         with:

bricks/_common/arm_none_eabi.mk

@@ -160,7 +160,7 @@ ifeq ($(PB_MCU_FAMILY),AT91SAM7)
 CFLAGS_MCU = -mthumb -mthumb-interwork -mtune=arm7tdmi -mcpu=arm7tdmi -msoft-float
 else
 ifeq ($(PB_MCU_FAMILY),TIAM1808)
-CFLAGS_MCU = -mcpu=arm926ej-s -Dgcc -Dam1808 # -c -g -fdata-sections -ffunction-sections -Wall -Dgcc -Dam1808 -O0
+CFLAGS_MCU = -mcpu=arm926ej-s -Dgcc -Dam1808
 else
 $(error unsupported PB_MCU_FAMILY)
 endif
@@ -196,8 +196,13 @@ else ifeq ($(DEBUG), 2)
 CFLAGS += -Os -DNDEBUG -flto=auto
 else
 CFLAGS += -Os -DNDEBUG -flto=auto
+ifneq ($(PB_MCU_FAMILY),TIAM1808)
+# This is used for trimming unused code on smaller platforms, but on EV3 we
+# don't want to enable these flags in order to keep the size of the .elf file
+# small by avoiding huge tables of section names.
 CFLAGS += -fdata-sections -ffunction-sections
 endif
+endif
 
 ifeq ($(PB_MCU_FAMILY),STM32)
 # Required for STM32 library
@@ -623,6 +628,10 @@ $(BUILD)/firmware.elf: $(LD_FILES) $(OBJ)
 	$(Q)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(OBJ) $(LIBS)
 	$(Q)$(SIZE) -A $@
 
+$(BUILD)/firmware.stripped.elf: $(BUILD)/firmware.elf
+	$(ECHO) "STRIP $@"
+	$(Q)$(STRIP) $< -o $@
+
 # firmware blob without checksum
 $(BUILD)/firmware-obj.bin: $(BUILD)/firmware.elf
 	$(ECHO) "BIN creating firmware base file"
@@ -635,13 +644,13 @@ ifeq ($(PB_MCU_FAMILY),TIAM1808)
 $(BUILD)/u-boot.bin:
 	$(ECHO) "Downloading u-boot.bin"
 	$(Q)mkdir -p $(dir $@)
-	$(Q)curl -sL -o $@ https://github.com/pybricks/u-boot/releases/download/pybricks/v1.0.2/u-boot.bin
-	$(Q)echo "62fe9df8138a4676d61b72c6844f9e7c3cbfd85470b9cea1418abec4f79228ac  $@" | sha256sum -c --strict
+	$(Q)curl -sL -o $@ https://github.com/pybricks/u-boot/releases/download/pybricks/v2.0.0/u-boot.bin
+	$(Q)echo "570e079870ddc1deb2ce40d7a4d6785c151883a65e273ce6e33643152df90efb  $@" | sha256sum -c --strict
 
 MAKE_BOOTABLE_IMAGE = $(PBTOP)/bricks/ev3/make_bootable_image.py
 
 # For EV3, merge firmware blob with u-boot to create a bootable image.
-$(BUILD)/firmware-base.bin: $(MAKE_BOOTABLE_IMAGE) $(BUILD)/u-boot.bin $(BUILD)/uImage
+$(BUILD)/firmware-base.bin: $(MAKE_BOOTABLE_IMAGE) $(BUILD)/u-boot.bin $(BUILD)/firmware.stripped.elf
 	$(Q)$^ $@
 
 else
@@ -664,12 +673,6 @@ $(BUILD)/firmware.zip: $(ZIP_FILES)
 	$(ECHO) "ZIP creating firmware package"
 	$(Q)$(ZIP) -j $@ $^
 
-# firmware in uImage format (for EV3)
-$(BUILD)/uImage: $(BUILD)/firmware-obj.bin $(BUILD)/firmware.elf
-	$(eval LOAD_ADDR := $(shell $(CROSS_COMPILE)readelf -l $(BUILD)/firmware.elf | grep "LOAD" | awk '{print $$4}'))
-	$(eval ENTRY_POINT := $(shell $(CROSS_COMPILE)readelf -h $(BUILD)/firmware.elf | grep "Entry point" | cut -d: -f2))
-	mkimage -C none -A arm -T standalone -O u-boot -a $(LOAD_ADDR) -e $(ENTRY_POINT) -d $< $@
-
 # PRU firmware
 $(BUILD)/pru_suart.bin.o: $(PBTOP)/lib/pbio/drv/uart/uart_ev3_pru_lib/pru_suart.bin
 	$(Q)$(OBJCOPY) -I binary -O elf32-littlearm -B arm \

bricks/ev3/README.md

@@ -24,12 +24,6 @@ firmware for one of the other targets, such as the SPIKE Prime Hub, as
 explained [here](../../CONTRIBUTING.md). Make sure that `pybricksdev` is
 installed.
 
-Install the following additional tools:
-
-```
-sudo apt install u-boot-tools
-```
-
 Unlike most other alternative EV3 firmware solutions, Pybricks does not require
 using a microSD card. Instead, Pybricks is installed as a firmware update.