I had a lot of mildew stains that even bleach/water would not take off. Found this Marine 31 stuff and it is amazing. It smells like concentrated bleach, but is far better than using bleach. It did an amazing job on my bass boat seats too.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I just sprayed it on the awning and rolled it up. Waited about 30 minutes unrolled it and sprayed it with the water hose. No scrubbing and it looks white as when it was new.