@z3ntu played around with the upstream kernel a bit. Freedreno is only one piece of the graphics puzzle. There’s the display controller and driver, for which @z3ntu threw together an initial driver which seemed to work but had some problems with running the display at full capacity (full HD at 60Hz). See his repository on Github for progress. There’s also the IOMMU that needs to be controlled for good GPU performance. From the top of my head the freedreno developer (Rob Clark) still struggles with integrating this IOMMU work into the kernel…
The reason why there isn’t a testing image out is because graphics isn’t the biggest problem. Trouble arises mainly with the baseband, which is in control of audio in unconventional ways. Having a public image out there that can’t connect to your mobile network seems a bit useless for a smartphone. You’d just risk people installing stuff and requiring support on things that should be deemed unsupported. Furthermore, each component needs to be hand-enabled in a file describing the hardware parameters (the device tree), and that requires extensive testing. Some bits have been done and are made upstream, but many peripherals don’t work yet.
Also! See this topic for more information!