Index or noindex mobile version?

[FCRMediaLietuva]

We have a website called imones.lt
and we have a mobile version for it m.imones.lt

We originally put noindex for m.imones.lt. Is it a good decision or no? We believe that if google indexes both it creates double content. We definitely don't want that? But when someone through google goes to any of imones.lt webpage using smartphone they are redirected to m.imones.lt/whatever

Thank you for your opinion.

[webmethod]

Google has a policy for this - what you're doing is not advisable - you should be annotating the URLs. You can read the correct approach to take here: https://developers.google.com/webmasters/mobile-sites/mobile-seo/configurations/separate-urls