Unable to start the M4F core

I refered to the SDK document

https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/09_00_00_03/exports/docs/linux/Foundational_Components_IPC62x.html?highlight=ipc

and wanted to start or stop m4f core,but got the following message,how to turn it on correctly?

root@BeaglePlay:/lib/firmware# echo stop > /sys/class/remoteproc/remoteproc0/state
bash: echo: write error: Invalid argument