On Mit, 2013-11-13 at 19:07 +0100, Jochen Rollwagen wrote:
I started investigating the problem because AGP mode used to work with the UMS drivers (although I now understand they didn’t really use AGP memory)
They used AGP memory but didn't dynamically bind memory to the AGP aperture or unbind it from there.
and in the second patch I mentioned below Benjamin Herrenschmidt stated that “there's a chip errata (for the pre-R600 chips). On those chips, the aperture must be aligned to the aperture size (that is FB_START in MC_FB_LOCATION must be aligned to the aperture size).” Since that workaround/patch definitely isn’t in the current DRM code any more (probably got lost in the transition to KMS) my idea was to re-apply the three-line workaround/patch (which should be quite trivial given the comment in radeon_vram_location in the drm kernel code).
So, have you verified that the aperture is not aligned to its size for you? If it's not, does aligning it help stability with AGP?