Surgery is required for a tear.
If it's tendinitis you may be able to work it out with rest and pain relievers. It's your body telling you to stretch and strengthen your shoulders. Don't neglect it or you will end up under the knife. I did and it's not fun. Turned into a 6 month healing process, and a full year before full recovery.

I agree with Barry. I had rotator cuff surgery on my left shoulder in January 2024. No club swings until almost June. Still working on regaining swing speed. Mine issue was from a car accident and had a complete tear.

I wouldn't mess with the tendonitis. Are you doing PT? or just anti inflamatories?? I'd ask the PT for some stretches and exercises to work on strengthening the shoulder. Also, you might want to check with your pro as to the cause of the tendonitis. If it's swing related, it will just return once you start swinging again.