Comment # 8 on bug 95017 from Mathieu Malaterre

(In reply to Ilia Mirkin from comment #7)
> FWIW on nouveau we just default agpmode=0 in a #ifdef __powerpc__. Perhaps
> the same thing can work for radeon.

Well radeon_agpmode is already set to 0 already[*]. My patch force to PCI(-1)
when user did not specify any value.

[*]https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/radeon/radeon_drv.c#L173