Getting u-boot logs on a CM5

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sahib: Posts: 13; Joined: Thu Apr 30, 2020 4:39 pm

Getting u-boot logs on a CM5

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Wed Nov 05, 2025 5:13 pm

Hi,

I'm stuck obtaining debug output from u-boot with a CM5.

Here's some context:

Im using a CM5 (the D0 variant precisely) with an CM5 IO Board.
Im in the process of porting an Yocto based OS from CM3/CM4s to CM5 & currently stuck getting ti to boot.
I do get debug logs from the rpi-firmware when holding a USB-TTL converter on the TX pin on the CM5 module itself. But I see no logs from u-boot. I do see the u-boot logo before it reboots though.
I'm running the last version of rpi-firmware (flashed with the recovery5 tool)
I know by now that there is UART10 (not directly accessible pins on the CM5 itself) und UART0 (the "old" GPIO 14/15 on the 40 pin header).
I've seen some reports that u-boot is capable of outputting logs to UART0 due to PCIe) connection between the main CPU and RP1.
I've checked the device-tree (bcm2712-rpi-cm5-cm5io.dtb) and see that both `stdout-path` and `console` are set to UART10, which should make u-boot use that one, but still nothing.
The u-boot I've used is just latest git master of u-boot with the vanilla rpi_arm64_defconfig.
Some other reports imply that u-boot gets stuck with spurios input, but in my case it just reboots.

Code: Select all

# config.txt
enable_uart=1
enable_rp1_uart=1
uart_2ndstage=1
pciex4_reset=0
# dtparam=uart0_console
# dtparam=uart0=on
# dtoverlay=uart0-pi5
dtoverlay=bcm2712d0
kernel=u-boot.bin

Code: Select all

# boot.conf
[all]
BOOT_UART=1
POWER_OFF_ON_HALT=1
# Boot Order Codes, from https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#BOOT_ORDER
# Try SD first (1), followed by, USB PCIe, NVMe PCIe, then network
BOOT_ORDER=0xf2461
# BOOT_ORDER=0xf1
UART_BAUD=115200
HDMI_DELAY=0
[email protected]/,6666@/

Boot log (the missing overlays were already fixed, don't mind them):

Code: Select all

RP1_UART 0000001c00030000
 6.31 Read /config.txt bytes 3209 hnd 0x2e79
 6.93 MESS:00:00:06.938524:0: Initial voltage 800000 temp 59812
 7.13 MESS:00:00:07.138971:0: avs_2712: AVS pred 8520 852000 temp 60911
 7.14 MESS:00:00:07.142604:0: vpred 852 mV +0
 7.15 MESS:00:00:07.151263:0: FB framebuffer_swap 1
 7.15 MESS:00:00:07.153233:0: Select resolution HDMI0/2 hotplug 0 max_mode 2
 7.16 MESS:00:00:07.160070:0: Select resolution HDMI1/2 hotplug 1 max_mode 2
 7.16 MESS:00:00:07.166934:0: FB0 disp 1 max-fb 1 1920x1080 stride 3840 base 0x3f800000
 7.19 MESS:00:00:07.196452:0: dtb_file 'bcm2712-rpi-cm5-cm5io.dtb'
 7.19 Loading 'bcm2712-rpi-cm5-cm5io.dtb' to 0x00000000 offset 0x100
 7.10 Read bcm2712-rpi-cm5-cm5io.dtb bytes 79739 hnd 0x61
 7.23 [sdcard] /overlays/overlay_map.dtb not found
 7.36 /overlays/overlay_map.dtb
 7.23 [sdcard] /overlays/bcm2712d0.dtbo not found
 7.43 /overlays/bcm2712d0.dtbo
 7.95 Read /config.txt bytes 3209 hnd 0x2e79
 7.29 MESS:00:00:07.297400:0: dtparam: uart0_console=true
 7.32 [sdcard] /overlays/uart0.dtbo not found
 7.26 /overlays/uart0.dtbo
 7.32 MESS:00:00:07.329255:0: dtparam: uart0=on
 7.27 Read /cmdline.txt bytes 104 hnd 0x60
 7.42 MESS:00:00:07.428906:0: Read command line from file 'cmdline.txt':
 7.43 MESS:00:00:07.435363:0: 'dwc_otg.lpm_enable=0 console=serial0,115200 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait net.ifnames=0'
 7.64 MESS:00:00:07.642582:0: RPM 0, max RPM 0
 7.69 BMD "armstub8-2712.bin" not found
 7.93 fs_open: 'armstub8-2712.bin'
 7.69 Loading uboot.bin' to 0x00000000 offset 0x200000
 7.30 Read uboot.bin bytes 653464 hnd 0x85
 7.73 MESS:00:00:07.732921:0: Kernel relocated to 0x80000
 7.73 MESS:00:00:07.737747:0: Device tree loaded to 0x2efec200 (size 0x13d17)
 7.74 Stopping network