How to find if my Photoshop CS6 has Retina support
Photoshop CS6 supports retina since version 13.0.3.
There is a blog article from Adobe about this  

How to update Photoshop:
1. In Photoshop, choose Help > Updates.
2. The Adobe Application Manager will launch. Select Adobe Photoshop CS6 and choose Update.

How to confirm that the Update worked
1. In Photoshop, choose Photoshop > About Photoshop (Mac)
2. For Mac perpetual customers, the version at the top should be Version: 13.0.3
3. For Win/Mac Creative Cloud members, the version at the top should be Version: 13.1.1