I am seeing somewhat identical error message in dmesg from my Mac Mini G4 (ppc) system with ATI:
[ 268.132457] [drm] radeon kernel modesetting enabled. [ 268.132645] bus: 'pci': add driver radeon [ 268.132735] bus: 'pci': driver_probe_device: matched device 0000:00:10.0 with driver radeon [ 268.132743] bus: 'pci': really_probe: probing driver radeon with device 0000:00:10.0 [ 268.132761] devices_kset: Moving 0000:00:10.0 to end of list [ 268.132773] checking generic (9c008000 5a000) vs hw (98000000 8000000) [ 268.132775] fb: switching to radeondrmfb from OFfb ATY,RockHo [ 268.133198] Console: switching to colour dummy device 80x25 [ 268.133225] device: 'fb0': device_unregister [ 268.133391] PM: Removing info for No Bus:fb0 [ 268.133485] device: 'fb0': device_create_release [ 268.133512] MM calling offb_destroy [ 268.133535] device: 'vtcon1': device_unregister [ 268.133576] PM: Removing info for No Bus:vtcon1 [ 268.133608] device: 'vtcon1': device_create_release [ 268.134018] radeon 0000:00:10.0: enabling device (0006 -> 0007) [ 268.134110] device: 'renderD128': device_add [ 268.134187] PM: Adding info for No Bus:renderD128 [ 268.141775] device: 'card0': device_add [ 268.141857] PM: Adding info for No Bus:card0 [ 268.142033] [drm] initializing kernel modesetting (RV280 0x1002:0x5962 0x1002:0x5962 0x01). [ 268.142061] MM dma_set_coherent_maskfailure [ 268.142213] radeon 0000:00:10.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0x0000 [ 268.142253] radeon 0000:00:10.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0x0000 [ 268.142670] [drm:radeon_get_bios [radeon]] *ERROR* Unable to locate a BIOS ROM [ 268.142764] [drm] Using device-tree clock info [ 268.142805] agpgart-uninorth 0000:00:0b.0: putting AGP V2 device into 4x mode [ 268.142818] radeon 0000:00:10.0: putting AGP V2 device into 4x mode [ 268.142863] radeon 0000:00:10.0: GTT: 256M 0x00000000 - 0x0FFFFFFF [ 268.142872] [drm] Generation 2 PCI interface, using max accessible memory [ 268.142885] radeon 0000:00:10.0: VRAM: 128M 0x0000000098000000 - 0x000000009FFFFFFF (32M used) [ 268.146575] [drm] Detected VRAM RAM=128M, BAR=128M [ 268.146604] [drm] RAM width 64bits DDR [ 268.146853] [TTM] Zone kernel: Available graphics memory: 255078 kiB [ 268.146868] [TTM] Initializing pool allocator [ 268.146998] [drm] radeon: 32M of VRAM memory ready [ 268.147014] [drm] radeon: 256M of GTT memory ready. [ 268.147685] radeon 0000:00:10.0: WB disabled [ 268.147710] radeon 0000:00:10.0: fence driver on ring 0 use gpu addr 0x0000000000000000 and cpu addr 0x29fa7e44 [ 268.147736] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [ 268.147745] [drm] Driver supports precise vblank timestamp query. [ 268.147793] [drm] radeon: irq initialized. [ 268.147830] [drm] Loading R200 Microcode [ 268.181869] [drm] radeon: ring at 0x0000000000001000 [ 268.181927] [drm] ring test succeeded in 0 usecs [ 268.183520] [drm] ib test succeeded in 0 usecs [ 268.183839] device: 'i2c-0': device_add [ 268.183882] bus: 'i2c': add device i2c-0 [ 268.183925] PM: Adding info for i2c:i2c-0 [ 268.183951] device: 'i2c-0': device_add [ 268.184014] PM: Adding info for No Bus:i2c-0 [ 268.184252] device: 'i2c-1': device_add [ 268.184287] bus: 'i2c': add device i2c-1 [ 268.184321] PM: Adding info for i2c:i2c-1 [ 268.184337] device: 'i2c-1': device_add [ 268.184393] PM: Adding info for No Bus:i2c-1 [ 268.184542] device: 'i2c-2': device_add [ 268.184568] bus: 'i2c': add device i2c-2 [ 268.184609] PM: Adding info for i2c:i2c-2 [ 268.184626] device: 'i2c-2': device_add [ 268.184680] PM: Adding info for No Bus:i2c-2 [ 268.184809] device: 'i2c-3': device_add [ 268.184831] bus: 'i2c': add device i2c-3 [ 268.184868] PM: Adding info for i2c:i2c-3 [ 268.184884] device: 'i2c-3': device_add [ 268.184954] PM: Adding info for No Bus:i2c-3 [ 268.185217] [drm] Connector Table: 7 (mini internal tmds) [ 268.185256] [drm] No TMDS info found in BIOS [ 268.185275] [drm] No TV DAC info found in BIOS [ 268.185316] device: 'card0-DVI-I-1': device_add [ 268.185388] PM: Adding info for No Bus:card0-DVI-I-1 [ 268.185496] device: 'card0-SVIDEO-1': device_add [ 268.185577] PM: Adding info for No Bus:card0-SVIDEO-1 [ 268.185644] [drm] Radeon Display Connectors [ 268.185657] [drm] Connector 0: [ 268.185664] [drm] DVI-I-1 [ 268.185671] [drm] HPD1 [ 268.185680] [drm] DDC: 0x6c 0x6c 0x6c 0x6c 0x6c 0x6c 0x6c 0x6c [ 268.185689] [drm] Encoders: [ 268.185697] [drm] DFP1: INTERNAL_TMDS1 [ 268.185706] [drm] CRT2: INTERNAL_DAC2 [ 268.185714] [drm] Connector 1: [ 268.185720] [drm] SVIDEO-1 [ 268.185727] [drm] Encoders: [ 268.185734] [drm] TV1: INTERNAL_DAC2 [ 268.233654] [drm] fb mappable at 0x98040000 [ 268.233688] [drm] vram apper at 0x98000000 [ 268.233696] [drm] size 1572864 [ 268.233704] [drm] fb depth is 16 [ 268.233711] [drm] pitch is 2048 [ 268.242378] device: 'fb0': device_add [ 268.242461] PM: Adding info for No Bus:fb0 [ 268.247502] device: 'vtcon1': device_add [ 268.247562] PM: Adding info for No Bus:vtcon1 [ 268.348381] Console: switching to colour frame buffer device 128x48 [ 268.371238] radeon 0000:00:10.0: fb0: radeondrmfb frame buffer device [ 268.371463] [drm] Initialized radeon 2.50.0 20080528 for 0000:00:10.0 on minor 0 [ 268.371608] driver: 'radeon': driver_bound: bound to device '0000:00:10.0' [ 268.371727] bus: 'pci': really_probe: bound device 0000:00:10.0 to driver radeon [ 334.235019] radeon 0000:00:10.0: ring 0 stalled for more than 10240msec [ 334.235038] radeon 0000:00:10.0: GPU lockup (current fence id 0x00000000000002bf last fence id 0x00000000000002c0 on ring 0) [ 334.746762] radeon 0000:00:10.0: ring 0 stalled for more than 10752msec [ 334.746781] radeon 0000:00:10.0: GPU lockup (current fence id 0x00000000000002bf last fence id 0x00000000000002c0 on ring 0) [ 335.258581] radeon 0000:00:10.0: ring 0 stalled for more than 11264msec [ 335.258599] radeon 0000:00:10.0: GPU lockup (current fence id 0x00000000000002bf last fence id 0x00000000000002c0 on ring 0) [ 335.770253] radeon 0000:00:10.0: ring 0 stalled for more than 11776msec [ 335.770270] radeon 0000:00:10.0: GPU lockup (current fence id 0x00000000000002bf last fence id 0x00000000000002c0 on ring 0) [ 336.281134] radeon 0000:00:10.0: ring 0 stalled for more than 12288msec [ 336.281152] radeon 0000:00:10.0: GPU lockup (current fence id 0x00000000000002bf last fence id 0x00000000000002c0 on ring 0) this is 100% reproducable. Just start kodi from it.