This is the Hart Software Services (HSS) code. On PolarFire SoC, this is comprised of two portions: A superloop monitor running on the E51 minion processor, which receives requests from the individual U54 application processors to perform certain services on their behalf; ...
The documentationexplains that the first two ports are used for “Hart Software Services (HSS) boot messages” (ttyUSB0) and U-Boot and Linux boot messages with a terminal prompt (ttyUSB1). The output from COM0 is pretty with a Microchip logo followed by messages from HSS which han...
The HSS is still present just that boot mode 0 is idle boot - you could re-program with the reference design job which should re-set the boot mode or re-build the HSS and either use the boot mode programmer in softconsole or use make program from the command line to program the eNVM ...