DRM support for platform devices dropped last year and was drastically improved earlier this year. Qualcomm uses it for a really weak DRM driver that handles memory for X but does GPU and display through a different interface. Feel free to flame me for that.. :).
https://www.codeaurora.org/gitweb/quic/la/?p=kernel/msm.git%3Ba=blob%3Bf=dri...
And I believe OMAP also has a solution somewhere (sorry, I couldn't find a URL).
Jordan