nouveau broken on Riva TNT2 in 5.9.0-rc8: GPU not supported on big-endian

[Ondrej Zary]

Hello,
I'm testing 5.9.0-rc8 and found that Riva TNT2 stopped working:
[    0.000000] Linux version 5.9.0-rc8+ (zary@gsql) (gcc (Debian 8.3.0-6) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #326 SMP Fri Oct 9 22:31:40 CEST 2020
...
[   14.771464] nouveau 0000:01:00.0: GPU not supported on big-endian
[   14.771782] nouveau: probe of 0000:01:00.0 failed with error -38

big-endian? WTF? The machine is x86.

It works fine with Debian 5.7 kernel (5.7.10-1~bpo10+1):
[    0.000000] Linux version 5.7.0-0.bpo.2-686 (debian-kernel@xxxxxxxxxxxxxxxx) (gcc version 8.3.0 (Debian 8.3.0-6), GNU ld (GNU Binutils for Debian) 2.31.1) #1 SMP Debian 5.7.10-1~bpo10+1 (2020-07-30)
...
[   23.266196] nouveau 0000:01:00.0: NVIDIA NV05 (20154000)
[   23.288582] nouveau 0000:01:00.0: bios: version 02.05.20.02.00
[   23.288869] nouveau 0000:01:00.0: bios: DCB table not found
[   23.289595] nouveau 0000:01:00.0: bios: DCB table not found
[   23.289956] nouveau 0000:01:00.0: bios: DCB table not found
[   23.290015] nouveau 0000:01:00.0: bios: DCB table not found
[   23.290215] agpgart-intel 0000:00:00.0: AGP 3.0 bridge
[   23.290287] agpgart-intel 0000:00:00.0: bridge is in legacy mode, falling back to 2.x
[   23.290351] agpgart-intel 0000:00:00.0: putting AGP V2 device into 4x mode
[   23.290430] nouveau 0000:01:00.0: putting AGP V2 device into 4x mode
[   23.290565] agpgart-intel 0000:00:00.0: AGP 3.0 bridge
[   23.290627] agpgart-intel 0000:00:00.0: bridge is in legacy mode, falling back to 2.x
[   23.290690] agpgart-intel 0000:00:00.0: putting AGP V2 device into 4x mode
[   23.290768] nouveau 0000:01:00.0: putting AGP V2 device into 4x mode
[   23.290830] nouveau 0000:01:00.0: tmr: unknown input clock freq
[   23.293026] nouveau 0000:01:00.0: fb: 32 MiB SDRAM
[   23.301269] [TTM] Zone  kernel: Available graphics memory: 382728 KiB
[   23.301327] [TTM] Initializing pool allocator
[   23.301414] nouveau 0000:01:00.0: DRM: VRAM: 31 MiB
[   23.301465] nouveau 0000:01:00.0: DRM: GART: 128 MiB
[   23.301518] nouveau 0000:01:00.0: DRM: BMP version 5.6
[   23.301570] nouveau 0000:01:00.0: DRM: No DCB data found in VBIOS
[   23.303594] nouveau 0000:01:00.0: DRM: MM: using M2MF for buffer copies
[   23.303719] nouveau 0000:01:00.0: bios: DCB table not found
[   23.304904] nouveau 0000:01:00.0: DRM: Saving VGA fonts
[   23.349089] nouveau 0000:01:00.0: DRM: No DCB data found in VBIOS
[   23.349681] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[   23.383066] nouveau 0000:01:00.0: DRM: allocated 1280x1024 fb: 0x4000, bo b10d2f17
[   23.413903] fbcon: nouveaudrmfb (fb0) is primary device
[   23.569851] Console: switching to colour frame buffer device 160x64
[   23.571050] nouveau 0000:01:00.0: fb0: nouveaudrmfb frame buffer device


-- 
Ondrej Zary