+1 to Paul's comment.
Upgrading service processors (SP) or baseboard management controllers (BMC) on FAS/AFF is nondisruptive to system data-serving operations, barring unforeseen issues.
It's always a great idea to reboot the SP or BMC before you perform any firmware upgrades (which is also nondisruptive). It potentially resolves any lingering/hidden issues that may exist and puts the SP/BMC in a "fresh" operating state for the maintenance. It's also a useful way to find out if there are any issues between ONTAP and the SP/BMC before you perform the upgrade.