Kernel parameters

Commonly used kernel parameters

dtb=

• microsoft-surface-rt.dtb for APX booting

• microsoft-surface-rt-efi.dtb for EFI booting

root=

Specifies the root filesystem which should be used.

• /dev/mmcblk0pN eMMC partition N

• /dev/mmcblk1pN µSD Card partition N

• /dev/sdaN USB partition N

console=

• tty0 for normal console (internal screen+tCover/USB keyboard)

• ttyS0,115200n8 for serial console at 115200 Baud, no parity bit, 8bits (need uart access)

You can specify multiple console= options on the kernel command line. Output will appear on all of them. The last device will be used when you open /dev/console. So, for example:

console=ttyS1,9600 console=tty0

defines that opening /dev/console will get you the current foreground virtual console, and kernel messages will appear on both the VGA console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.

Note that you can only define one console per device type (serial, video). - https://www.kernel.org/doc/html/latest/admin-guide/serial-console.html

rootwait

Waits for root filesystem. Some root filesystems will be mounted after the kernel finished initalizing hardware. Thats the case for USB. eMMC/SD seems to work without this parameter.

cpuidle.off=1

EFI doesn't support CPU idle therefore it must be disabled for efi booting. You shouldn't use this param for APX booting.