$ git clone https://source.codeaurora.org/external/imx/imx-atf -b imx_5.4.24_2.1.0

$ cd imx-atf

$ wget -c ftp://ftp.embedian.com/public/smarcimx8m/0001-imx8m-atf-ddr-timing.patch

$ patch -p1 <0001-imx8m-atf-ddr-timing.patch

$ make CROSS_COMPILE=${CC} PLAT=imx8mq bl31

$ cp build/imx8mq/release/bl31.bin ../imx-mkimage/iMX8M/

$ cd ../

Note1:

If the board is 2GB LPDDR4 in commercial or industrial temperature, use
$ make ARCH=arm CROSS_COMPILE=${CC} smarcimx8mq_2g_ser3_defconfig

If the board is SMARC-iMX8M-Q-4G or SMARC-iMX8M-Q-4G-I (4GB LPDDR4), use
$ make ARCH=arm CROSS_COMPILE=${CC} smarcimx8mq_4g_ser3_defconfig

Note 2:

"ser3" stands for console debug port in SMARC definition. In this example, we uses SER3 as debug port. If user uses SER0 as your debug port, make change to "ser0" instead. Same as SER1 and SER2.

Note 3:

To change the debug port, in addition to u-boot defconfig and uEnv.txt files, you also need to modify plat/imx/imx8m/imx8mq/include/platform_def.h in the imx-atf. Find "#define IMX_BOOT_UART_BASE U(0x30860000)" and change to the correct address that defined in uEnv.txt file.

Note 4:

The SMARC-iMX8M module always boot up from the on-module eMMC flash. The factory default will be flash.bin pre-installed with SER3 as console output. In some cases when the eMMC flash is empty or needs to be upgraded. Users can shunt crossed the TEST# to ground. In this way, the SMARC-iMX8M module will boot up to carrier SD card, if TEST# pin is shunt crossed. The flash.bin image are the same, the difference is how you flash flash.bin. This will be explained in the "Setup SD card" section.