Radeon RV100 init fails with specific card+mobo - IRQ problem

[Meelis Roos <mroos@linux.ee>]

I have a test PC with AMD 760MPX chipset (Tyan S2466 Tiger MPX board) 
and Radeon RV100-based AGP card where radeon KMS modesetting does not 
work (does not work with any kernel tried so far (2.6.32, 3.2, 3.7, 
3.8-rc6).

>From dmesg with drm.debug=0xc 

[    3.209617] agpgart-amdk7 0000:00:00.0: AMD 760MP chipset
[    3.325408] agpgart-amdk7 0000:00:00.0: AGP aperture is 512M @ 0xc0000000
[...]
[    3.529106] [drm] Initialized drm 1.1.0 20060810
[    3.797715] [drm] radeon defaulting to kernel modesetting.
[    3.797817] [drm] radeon kernel modesetting enabled.
[    3.799108] [drm] initializing kernel modesetting (RV100 0x1002:0x5159 0x1787:0x0F02).
[    3.799277] [drm] register mmio base: 0xB2000000
[    3.799354] [drm] register mmio size: 65536
[    3.799629] agpgart-amdk7 0000:00:00.0: AGP 2.0 bridge
[    3.799718] agpgart-amdk7 0000:00:00.0: putting AGP V2 device into 4x mode
[    3.799811] radeon 0000:01:05.0: putting AGP V2 device into 4x mode
[    3.799900] radeon 0000:01:05.0: GTT: 512M 0xC0000000 - 0xDFFFFFFF
[    3.799985] radeon 0000:01:05.0: VRAM: 128M 0x00000000E0000000 - 0x00000000E7FFFFFF (64M used)
[    3.800187] [drm] Supports vblank timestamp caching Rev 1 (10.10.2010).
[    3.800268] [drm] Driver supports precise vblank timestamp query.
[    3.800350] radeon 0000:01:05.0: Fatal error during GPU init
[    3.800432] [drm] radeon: finishing device.
[    3.800509] [TTM] Memory type 2 has not been initialized
[    3.800590] [drm] radeon: cp finalized
[    3.800756] radeon: probe of 0000:01:05.0 failed with error -22


01:05.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI RV100 QY [Radeon 7000/VE] [1002:5159] (prog-if 00 [VGA controller])
        Subsystem: Hightech Information System Ltd. Device [1787:0f02]
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping+ SERR- FastB2B+ DisINTx-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Region 0: Memory at e0000000 (32-bit, prefetchable) [size=128M]
        Region 1: I/O ports at 2000 [size=256]
        Region 2: Memory at b2000000 (32-bit, non-prefetchable) [size=64K]
        [virtual] Expansion ROM at b2020000 [disabled] [size=128K]
        Capabilities: [58] AGP version 2.0
                Status: RQ=48 Iso- ArqSz=0 Cal=0 SBA+ ITACoh- GART64- HTrans- 64bit- FW- AGP3- Rate=x1,x2,x4
                Command: RQ=16 ArqSz=0 Cal=0 SBA+ AGP+ GART64- 64bit- FW- Rate=x4
        Capabilities: [50] Power Management version 2
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-

Adding some printks reveals it calls
r100_init() -> radeon_irq_kms_init() -> drm_irq_install() -> 
drm_dev_to_irq() and that fails. So no IRQ, no KMS.

lspci does not show Interrupt like on some other PCI devices. 
/proc/interrupts obviously does not contain the irq since we do not 
register any yet.

There is no BIOS option of "Enable IRQ for VGA" or similar (BIOS is 
latest). Could this be the problem?

What can I do to get KMS working on this computer?

-- 
Meelis Roos (mroos@linux.ee)