Beacuse of PTI, I decided to test 4.15-rc6 on most of my test machines. And I happened to notice a radeon problem on RV250 era card with no monitor attached. 4.15-rc1 and earlier kernels did not show these errors, not kernels between rc1 and rc6 have been tested yet.

The messages in dmes are strange, like 2 threads trying to poke the card instead of one? Or is it just rrying AGP mode and then PCI mode and this double output is OK?

[ 4.777185] [drm] radeon kernel modesetting enabled. [ 4.779418] [drm] initializing kernel modesetting (RV250 0x1002:0x4966 0x1458:0x4010 0x01). [ 4.779888] agpgart-amdk7 0000:00:00.0: AGP 2.0 bridge [ 4.779963] agpgart-amdk7 0000:00:00.0: putting AGP V2 device into 4x mode [ 4.780106] radeon 0000:01:05.0: putting AGP V2 device into 4x mode [ 4.780179] radeon 0000:01:05.0: GTT: 512M 0xC0000000 - 0xDFFFFFFF [ 4.780249] radeon 0000:01:05.0: VRAM: 128M 0x00000000E0000000 - 0x00000000E7FFFFFF (64M used) [ 4.780344] [drm] Detected VRAM RAM=128M, BAR=128M [ 4.780405] [drm] RAM width 128bits DDR [ 4.780622] [TTM] Zone kernel: Available graphics memory: 439294 kiB [ 4.780686] [TTM] Zone highmem: Available graphics memory: 1032930 kiB [ 4.780749] [TTM] Initializing pool allocator [ 4.780898] [drm] radeon: 64M of VRAM memory ready [ 4.780961] [drm] radeon: 512M of GTT memory ready. [ 4.783068] radeon 0000:01:05.0: WB disabled [ 4.783166] radeon 0000:01:05.0: fence driver on ring 0 use gpu addr 0x00000000c0000000 and cpu addr 0xf6a59461 [ 4.783261] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [ 4.783323] [drm] Driver supports precise vblank timestamp query. [ 4.783447] [drm] radeon: irq initialized. [ 4.783509] [drm] Loading R200 Microcode [ 4.819844] [drm] radeon: ring at 0x00000000C0001000 [ 4.923034] [drm:r100_ring_test [radeon]] *ERROR* radeon: ring test failed (scratch(0x15E4)=0xCAFEDEAD) [ 4.923181] [drm:r100_cp_init [radeon]] *ERROR* radeon: cp isn't working (-22). [ 4.923271] radeon 0000:01:05.0: failed initializing CP (-22). [ 4.923332] radeon 0000:01:05.0: Disabling GPU acceleration [ 5.025789] [drm:r100_cp_fini [radeon]] *ERROR* Wait for CP idle timeout, shutting down CP. [ 5.026022] [drm] radeon: cp finalized [ 5.026128] [drm] radeon: cp finalized [ 5.026223] [TTM] Finalizing pool allocator [ 5.027245] [TTM] Zone kernel: Used memory at exit: 0 kiB [ 5.027331] [TTM] Zone highmem: Used memory at exit: 0 kiB [ 5.027397] [drm] radeon: ttm finalized [ 5.027468] [drm] Forcing AGP to PCI mode [ 5.027886] radeon 0000:01:05.0: VRAM: 128M 0x00000000E0000000 - 0x00000000E7FFFFFF (64M used) [ 5.028577] radeon 0000:01:05.0: GTT: 512M 0x00000000C0000000 - 0x00000000DFFFFFFF [ 5.028671] [drm] Detected VRAM RAM=128M, BAR=128M [ 5.028730] [drm] RAM width 128bits DDR [ 5.028942] [TTM] Zone kernel: Available graphics memory: 439294 kiB [ 5.029005] [TTM] Zone highmem: Available graphics memory: 1032930 kiB [ 5.029066] [TTM] Initializing pool allocator [ 5.029216] [drm] radeon: 64M of VRAM memory ready [ 5.029277] [drm] radeon: 512M of GTT memory ready. [ 5.029342] [drm] GART: num cpu pages 131072, num gpu pages 131072 [ 5.034222] [drm] PCI GART of 512M enabled (table at 0x0000000035600000). [ 5.034393] radeon 0000:01:05.0: WB disabled [ 5.034465] radeon 0000:01:05.0: fence driver on ring 0 use gpu addr 0x00000000c0000000 and cpu addr 0x516b4fc4 [ 5.034557] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [ 5.034618] [drm] Driver supports precise vblank timestamp query. [ 5.034729] [drm] radeon: irq initialized. [ 5.034984] [drm] radeon: ring at 0x00000000C0001000 [ 5.138470] [drm:r100_ring_test [radeon]] *ERROR* radeon: ring test failed (scratch(0x15E4)=0xCAFEDEAD) [ 5.138618] [drm:r100_cp_init [radeon]] *ERROR* radeon: cp isn't working (-22). [ 5.138704] radeon 0000:01:05.0: failed initializing CP (-22). [ 5.138764] radeon 0000:01:05.0: Disabling GPU acceleration [ 5.241223] [drm:r100_cp_fini [radeon]] *ERROR* Wait for CP idle timeout, shutting down CP. [ 5.241408] [drm] radeon: cp finalized [ 5.243484] [drm] No TV DAC info found in BIOS [ 5.243659] [drm] Radeon Display Connectors [ 5.243719] [drm] Connector 0: [ 5.243776] [drm] VGA-1 [ 5.243833] [drm] DDC: 0x60 0x60 0x60 0x60 0x60 0x60 0x60 0x60 [ 5.243894] [drm] Encoders: [ 5.243951] [drm] CRT1: INTERNAL_DAC1 [ 5.244064] [drm] Connector 1: [ 5.244120] [drm] DVI-I-1 [ 5.244176] [drm] HPD1 [ 5.244231] [drm] DDC: 0x64 0x64 0x64 0x64 0x64 0x64 0x64 0x64 [ 5.244291] [drm] Encoders: [ 5.244346] [drm] CRT2: INTERNAL_DAC2 [ 5.244404] [drm] DFP1: INTERNAL_TMDS1 [ 5.244460] [drm] Connector 2: [ 5.244516] [drm] SVIDEO-1 [ 5.244571] [drm] Encoders: [ 5.244626] [drm] TV1: INTERNAL_DAC2 [ 5.262348] [drm] Cannot find any crtc or sizes [ 5.262491] [drm] Initialized radeon 2.50.0 20080528 for 0000:01:05.0 on minor 0 [ 6.290422] [drm] Cannot find any crtc or sizes