Hi Adam, Looking at your imx8mn beacon patches, it seems you managed to boot the imx8mn beacon board via serial download mode.
I am trying to achieve the same on an imx8mn-evk running top of tree U-Boot and added the following changes: --- a/configs/imx8mn_evk_defconfig +++ b/configs/imx8mn_evk_defconfig @@ -50,11 +50,22 @@ CONFIG_CMD_GPIO=y CONFIG_CMD_I2C=y CONFIG_CMD_MMC=y CONFIG_CMD_CACHE=y +CONFIG_USB=y +# CONFIG_SPL_DM_USB is not set +CONFIG_USB_EHCI_HCD=y +CONFIG_USB_GADGET=y +CONFIG_USB_GADGET_MANUFACTURER="FSL" +CONFIG_USB_GADGET_VENDOR_NUM=0x0525 +CONFIG_USB_GADGET_PRODUCT_NUM=0xa4a5 +CONFIG_CI_UDC=y +CONFIG_SDP_LOADADDR=0x0 +CONFIG_OF_LIBFDT_OVERLAY=y CONFIG_CMD_REGULATOR=y CONFIG_CMD_EXT4_WRITE=y CONFIG_OF_CONTROL=y CONFIG_SPL_OF_CONTROL=y CONFIG_ENV_OVERWRITE=y +CONFIG_ENV_IS_NOWHERE=y CONFIG_ENV_IS_IN_MMC=y CONFIG_SYS_RELOC_GD_ENV_ADDR=y CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y Then I put the board into serial download mode and I run: $ sudo uuu flash.bin The following output appears on the console: U-Boot SPL 2022.04-00856-g246e03476ba3-dirty (Apr 20 2022 - 16:24:48 -0300) SEC0: RNG instantiated Normal Boot WDT: Started watchdog@30280000 with servicing (60s timeout) Trying to boot from BOOTROM Find img info 0x&48020a00, size 872 Need continue download 1024 Download 694696, Total size 696232 NOTICE: BL31: v2.2(release):rel_imx_5.4.47_2.2.0-0-gc949a888e909 NOTICE: BL31: Built : 16:07:45, Apr 20 2022 What would be the other uuu command that needs to be run so that U-Boot proper can be loaded? Thanks, Fabio Estevam