This page is still mostly a stub, please add to it!
PowerVR is a line of GPU by Imagination Technologies. It has zero Free Software/Open Source support right now, and the associated development effort seems to be regarded as very high. Imagination has hinted they were considering addressssing the problem but today the position seem to be still open
It is regarded as more powerful than the Mali400 GPU found in other SoCs (needs ref).
Imagination Technologies published a linux driver for their binary microkernel under a dual license: MIT & GPL v2. 
on 2022 Imagination Tech is publishing a new open-source driver, both on DRM side  and Mesa Vulkan driver . Imagination's driver focus on their newer PowerVR "Rogue" GPUs starting from series6XT (for example the GX6250, dated Jan 2014), but maybe with minor modification this driver can be used on older series6 (like G6230, dated Jun 2012).
Allwinner SoC with a PowerVR GPU:
|A31||SGX544 or SGX544MP2||1.1.5|
- http://www.cnx-software.com/2015/06/18/open-source-linux-drivers-for-powervr-gpus-might-be-in-the-works/ CNX blog entry
- https://careers.imgtec.com/#/vacancy/details/2619 Open position at Imagination Technologies
- http://www.fsf.org/campaigns/priority.html High Priority Free Software Projects
- http://powervr.gnu.org.ve/doku.php Collecting information about the PowerVR architecture
- https://github.com/LeMaker/linux-actions/tree/linux-3.10.y/drivers/gpu/pvr LeMaker Integrated it into their 3.10.y kernel
- https://lore.kernel.org/all/[email protected]/