Hi, I booting the m4 with followed: m4boot=fatload mmc 0:1 0x80800000 cortex_m4_bsp.bin;cp.l 0x80800000 0x007f8000 2048;mw.l 0x020d8000 0xa0480539;mw.l 0x020d8000 0xa0480529; The example, see below, only print a String. But while A9 is booting I only get undefined symbols I defined the uart_from_osz environment variable, in reason of https://community.nxp.com/thread/349097 m4mmcargs=uart_from_osc clk_ignore_unused cpuidle.off=1 and now I got after completed boot the correct string. But why not after booting the m4? And why I get the login directive from the A9 on this UART too? I activate the UART2 over the DeviceTreeConfigurator and the uart ist also defined in the example.
Did you solve the problem? As far as I understand, your problem is related to you actually activate "status=okay" the uart2 in device tree for m4 which is totally wrong. If you want to use a device in M4 domain, you need to obligatorily deactivate the module in device tree "status=disable". The worst part about this issue with uart2 is when you use "device tree editor" and select uart2 in the correct pins (because you want to use in m4 and that is the intention of "device tree editor"), this actually generate a new device tree binary which of course activate uart2 with status=okay and you experiment the behaivor of seeing logging string. I am almost tired to try tune udoobuntu for m4, I think I will change to yocto from official source in NXP.
