drm_get_resource_start() gets an rman resource start, which is not always physical address. On PowerPC, and any architecture that uses OFW/FDT, the resources are specified in PCI space, not physical address space. This causes the wrong mappings to be generated, potentially stomping on real memory.
Hi! Is this still an issue?
No longer an issue. The issue was fixed in github 1e4fa87.