Raspberry Pi 4B + U-Boot bootloader - device tree addresses (.dtb) - raspberry-pi

Question

I compiled U-Boot (#v2022.01-rc1) with untouched rpi_4_defconfig. The U-Boot loads into shell successfuly, however
entering this sequence of commands will get stuck on "Starting kernel ...":
setenv serverip 192.168.0.1
setenv ipaddr 192.168.0.10
setenv kernel_comp_addr_r 0x0A000000
setenv kernel_comp_size 7921972
tftp ${kernel_addr_r} kernel8.img
tftp ${fdt_addr_r} bcm2711-rpi-4-b.dtb
booti ${kernel_addr_r} - ${fdt_addr_r} // Gets stuck at Starting kernel...
However, if I replace ${fdt_addr_r} with ${fdt_addr} in booti command it will load the kernel successfully. Like this:
booti ${kernel_addr_r} - ${fdt_addr} // Works fine
What is the difference between ${fdt_addr_r} and ${fdt_addr}? Why doesn't my first approach work? Why does ${fdt_addr} work?
DEBUG INFO:
RPi firmware boot logs:
Read start4.elf bytes 2228768 hnd 0x00000072
Read fixup4.dat bytes 5446 hnd 0x00000067
Firmware: d7f29d96450abfc77cd6cf011af1faf1e03e5e56 Apr 30 2021 13:45:52
0x00c03112 0x00000000 0x000000ff
MEM GPU: 76 ARM: 948 TOTAL: 1024
Starting start4.elf # 0xfec00200 partition 0
PCI reset
+
MESS:00:00:05.184648:0: arasan: arasan_emmc_open
MESS:00:00:05.332928:0: brfs: File read: /mfs/sd/config.txt
MESS:00:00:05.335639:0: brfs: File read: 81 bytes
MESS:00:00:05.402894:0: brfs: File read: /mfs/sd/config.txt
MESS:00:00:05.421071:0: brfs: File read: 81 bytes
MESS:00:00:05.902232:0: gpioman: gpioman_get_pin_num: pin DISPLAY_DSI_PORT not defined
MESS:00:00:05.909524:0: *** Restart logging
MESS:00:00:05.914477:0: hdmi: HDMI:hdmi_get_state is deprecated, use hdmi_get_display_state instead
MESS:00:00:05.923831:0: hdmi: HDMI:hdmi_get_state is deprecated, use hdmi_get_display_state instead
MESS:00:00:05.929762:0: HDMI0: hdmi_pixel_encoding: 300000000
MESS:00:00:05.935229:0: HDMI1: hdmi_pixel_encoding: 300000000
MESS:00:00:05.945421:0: dtb_file 'bcm2711-rpi-4-b.dtb'
MESS:00:00:05.952218:0: brfs: File read: /mfs/sd/bcm2711-rpi-4-b.dtb
MESS:00:00:05.955466:0: Loading 'bcm2711-rpi-4-b.dtb' to 0x100 size 0xc2a9
MESS:00:00:05.974659:0: brfs: File read: 49833 bytes
MESS:00:00:06.039897:0: brfs: File read: /mfs/sd/config.txt
MESS:00:00:06.042389:0: brfs: File read: 81 bytes
MESS:00:00:06.047663:0: brfs: File read: /mfs/sd/overlays/disable-bt.dtbo
MESS:00:00:06.067534:0: Loaded overlay 'disable-bt'
MESS:00:00:06.107041:0: brfs: File read: 1073 bytes
MESS:00:00:06.108885:0: Failed to open command line file 'cmdline.txt'
MESS:00:00:07.249713:0: brfs: File read: /mfs/sd/u-boot.bin
MESS:00:00:07.252181:0: Loading 'u-boot.bin' to 0x80000 size 0x8f720
MESS:00:00:07.258265:0: Device tree loaded to 0x2eff3800 (size 0xc743)
MESS:00:00:07.266568:0: uart: Set PL011 baud rate to 103448.300000 Hz
MESS:00:00:07.273628:0: uart: Baud rate change done...
MESS:00:00:07.275688:0: uart: Baud rate change done...
MESS:00:00:07.281220:0: gpioman: gpioman_get_pin_num: pin SDCARD_CONTROL_POWER not defined
U-Boot log:
U-Boot 2022.01-rc1 (Nov 11 2021 - 15:59:50 +0100)
DRAM: 3.9 GiB
RPI 4 Model B (0xc03112)
MMC: mmcnr#7e300000: 1, mmc#7e340000: 0
Loading Environment from FAT... Unable to read "uboot.env" from mmc0:1... In: serial
Out: serial
Err: serial
Net: eth0: ethernet#7d580000
PCIe BRCM: link up, 5.0 Gbps x1 (SSC)
starting USB...
Bus xhci_pci: Register 5000420 NbrPorts 5
Starting the controller
USB XHCI 1.00
scanning bus xhci_pci for devices... 2 USB Device(s) found
scanning usb for storage devices... 0 Storage Device(s) found
Hit any key to stop autoboot: 2
U-boot environment (without entering any commands, or modifying env in any way):
arch=arm
baudrate=115200
board=rpi
board_name=4 Model B
board_rev=0x11
board_rev_scheme=1
board_revision=0xC03112
boot_a_script=load ${devtype} ${devnum}:${distro_bootpart} ${scriptaddr} ${prefix}${script}; source ${scriptaddr}
boot_efi_binary=load ${devtype} ${devnum}:${distro_bootpart} ${kernel_addr_r} efi/boot/bootaa64.efi; if fdt addr ${fdt_addr_r}; then bootefi ${kernel_addr_r} ${fdt_addr_r};else bootefi ${kernel_addr_r} ${fdtcontroladdr};fi
boot_efi_bootmgr=if fdt addr ${fdt_addr_r}; then bootefi bootmgr ${fdt_addr_r};else bootefi bootmgr;fi
boot_extlinux=sysboot ${devtype} ${devnum}:${distro_bootpart} any ${scriptaddr} ${prefix}${boot_syslinux_conf}
boot_net_usb_start=usb start
boot_pci_enum=pci enum
boot_prefixes=/ /boot/
boot_script_dhcp=boot.scr.uimg
boot_scripts=boot.scr.uimg boot.scr
boot_syslinux_conf=extlinux/extlinux.conf
boot_targets=mmc0 mmc1 usb0 pxe dhcp
bootcmd=run distro_bootcmd
bootcmd_dhcp=devtype=dhcp; run boot_net_usb_start; run boot_pci_enum; if dhcp ${scriptaddr} ${boot_script_dhcp}; then source ${scriptaddr}; fi;setenv efi_fdtfile ${fdtfile}; setenv efi_old_vci ${bootp_vci};setenv efi_old_arch ${bootp_arch};setenv bootp_vci PXEClient:Arch:00011:UNDI:003000;setenv bootp_arch 0xb;if dhcp ${kernel_addr_r}; then tftpboot ${fdt_addr_r} dtb/${efi_fdtfile};if fdt addr ${fdt_addr_r}; then bootefi ${kernel_addr_r} ${fdt_addr_r}; else bootefi ${kernel_addr_r} ${fdtcontroladdr};fi;fi;setenv bootp_vci ${efi_old_vci};setenv bootp_arch ${efi_old_arch};setenv efi_fdtfile;setenv efi_old_arch;setenv efi_old_vci;
bootcmd_mmc0=devnum=0; run mmc_boot
bootcmd_mmc1=devnum=1; run mmc_boot
bootcmd_pxe=run boot_net_usb_start; run boot_pci_enum; dhcp; if pxe get; then pxe boot; fi
bootcmd_usb0=devnum=0; run usb_boot
bootdelay=2
cpu=armv8
dfu_alt_info=u-boot.bin fat 0 1;uboot.env fat 0 1;config.txt fat 0 1;Image fat 0 1
dhcpuboot=usb start; dhcp u-boot.uimg; bootm
distro_bootcmd=for target in ${boot_targets}; do run bootcmd_${target}; done
efi_dtb_prefixes=/ /dtb/ /dtb/current/
ethaddr=dc:a6:32:5f:91:f4
fdt_addr=2eff3800
fdt_addr_r=0x02600000
fdt_high=ffffffffffffffff
fdtcontroladdr=3af44630
fdtfile=broadcom/bcm2711-rpi-4-b.dtb
initrd_high=ffffffffffffffff
kernel_addr_r=0x00080000
load_efi_dtb=load ${devtype} ${devnum}:${distro_bootpart} ${fdt_addr_r} ${prefix}${efi_fdtfile}
loadaddr=0x1000000
mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi
preboot=pci enum; usb start;
pxefile_addr_r=0x02500000
ramdisk_addr_r=0x02700000
scan_dev_for_boot=echo Scanning ${devtype} ${devnum}:${distro_bootpart}...; for prefix in ${boot_prefixes}; do run scan_dev_for_extlinux; run scan_dev_for_scripts; done;run scan_dev_for_efi;
scan_dev_for_boot_part=part list ${devtype} ${devnum} -bootable devplist; env exists devplist || setenv devplist 1; for distro_bootpart in ${devplist}; do if fstype ${devtype} ${devnum}:${distro_bootpart} bootfstype; then run scan_dev_for_boot; fi; done; setenv devplist
scan_dev_for_efi=setenv efi_fdtfile ${fdtfile}; for prefix in ${efi_dtb_prefixes}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${efi_fdtfile}; then run load_efi_dtb; fi;done;run boot_efi_bootmgr;if test -e ${devtype} ${devnum}:${distro_bootpart} efi/boot/bootaa64.efi; then echo Found EFI removable media binary efi/boot/bootaa64.efi; run boot_efi_binary; echo EFI LOAD FAILED: continuing...; fi; setenv efi_fdtfile
scan_dev_for_extlinux=if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${boot_syslinux_conf}; then echo Found ${prefix}${boot_syslinux_conf}; run boot_extlinux; echo SCRIPT FAILED: continuing...; fi
scan_dev_for_scripts=for script in ${boot_scripts}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${script}; then echo Found U-Boot script ${prefix}${script}; run boot_a_script; echo SCRIPT FAILED: continuing...; fi; done
scriptaddr=0x02400000
serial#=100000009b911a03
soc=bcm283x
stderr=serial,vidconsole
stdin=serial,usbkbd
stdout=serial,vidconsole
usb_boot=usb start; if usb dev ${devnum}; then devtype=usb; run scan_dev_for_boot_part; fi
usbethaddr=dc:a6:32:5f:91:f4
vendor=raspberrypi
Environment size: 4113/16380 bytes
U-boot process of entering commands and booting the kernel:
U-Boot> setenv serverip 192.168.0.1
U-Boot> setenv ipaddr 192.168.0.10
U-Boot> setenv kernel_comp_addr_r 0x0A000000
U-Boot> setenv kernel_comp_size 7921972
U-Boot> tftp ${kernel_addr_r} kernel8.img
Using ethernet#7d580000 device
TFTP from server 192.168.0.1; our IP address is 192.168.0.10
Filename 'kernel8.img'.
Load address: 0x80000
Loading: *################################################## 7.6 MiB
13.9 MiB/s
done
Bytes transferred = 7921972 (78e134 hex)
U-Boot> tftp ${fdt_addr_r} bcm2711-rpi-4-b.dtb
Using ethernet#7d580000 device
TFTP from server 192.168.0.1; our IP address is 192.168.0.10
Filename 'bcm2711-rpi-4-b.dtb'.
Load address: 0x2600000
Loading: *################################################## 48.7 KiB
5.3 MiB/s
done
Bytes transferred = 49833 (c2a9 hex)
U-Boot> booti ${kernel_addr_r} - ${fdt_addr_r}
Uncompressing Kernel Image
Moving Image from 0x80000 to 0x200000, end=17f0000
## Flattened Device Tree blob at 02600000
Booting using the fdt blob at 0x2600000
Using Device Tree in place at 0000000002600000, end 000000000260f2a8
Starting kernel ... // <------ !!!! stuck here forever

Answer 1

Regarding ${fdt_addr} and ${fdt_addr_r}:
The u-boot rpi_4_defconfig configures CONFIG_OF_BOARD. By this option u-boot does not use its own device tree, but it receives the device tree which is provided by the eeprom bootloader of the Raspberry Pi 4. The RPi bootloader already prepares the device tree depending on the options in the file config.txt of the boot partition, including dt-overlays and including bootargs specified in cmdline.txt.
So the device tree located at address ${fdt_addr} is the device tree prepared by the Raspberry Pi bootloader. This might be the reason why booting using ${fdt_addr} works. As a consequence, you don't have to necessarily prepare and load a device tree on your own on the Raspberry Pi. You could just reuse ${fdt_addr} in the u-boot booti command as it is already loaded.
If you choose to load your own device tree, compare its contents with the configuration in config.txt (especially the dtoverlay=..). Also check cmdline.txt for bootargs. In your u-boot command list you did not set any bootargs with setenv bootargs ....
As mentioned by sawdust you could use setenv bootargs 'earlycon=uart8250,mmio32,0xfe215040 console=serial0,115200 ...' for getting debug infos on the miniuart serial line.