(In reply to Bernhard Rosenkraenzer from comment #0)

> 
> I presume the problem is caused by the (lack of) BIOS on aarch64 boards not
> initializing the GPU the same way an x86 box does.
> 

No, the driver is able to init the card regardless of whether the vbios has
been posted or not.

> This is on kernel 4.4.52 (latest kernel supported by the board; could try
> pulling DRI patches from newer kernels if there's any hope of changes being
> there already), libdrm 2.4.82

Here's the problem:

> [Wed Jul 12 14:01:10 2017] [drm] Detected VRAM RAM=512M, BAR=0M

There is no PCI BAR for frame buffer access. I'm guessing your pcie bridge does
not have a large enough aperture for the frame buffer BAR.  It's generally
256MB.

The driver can't work without access to vram.

Please attach your full dmesg output.