if (rdev->flags & RADEON_IS_IGP)
                base = (RREG32(RADEON_NB_TOM) & 0xffff) << 16;
        radeon_vram_location(rdev, &rdev->mc, base);
+       rdev->mc.gtt_base_align = 0;
        if (!(rdev->flags & RADEON_IS_AGP))
                radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);
 
        if (rdev->flags & RADEON_IS_IGP)
                base = (RREG32(RADEON_NB_TOM) & 0xffff) << 16;
        radeon_vram_location(rdev, &rdev->mc, base);
+       rdev->mc.gtt_base_align = 0;
        if (!(rdev->flags & RADEON_IS_AGP))
                radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);
 
        r520_vram_get_type(rdev);
        r100_vram_init_sizes(rdev);
        radeon_vram_location(rdev, &rdev->mc, 0);
+       rdev->mc.gtt_base_align = 0;
        if (!(rdev->flags & RADEON_IS_AGP))
                radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);
 
                if (rdev->flags & RADEON_IS_IGP)
                        base = (RREG32(MC_VM_FB_LOCATION) & 0xFFFF) << 24;
                radeon_vram_location(rdev, &rdev->mc, base);
+               rdev->mc.gtt_base_align = 0;
                radeon_gtt_location(rdev, mc);
        }
 }
 
        int                     vram_mtrr;
        bool                    vram_is_ddr;
        bool                    igp_sideport_enabled;
+       u64                     gtt_base_align;
 };
 
 bool radeon_combios_sideport_present(struct radeon_device *rdev);
 
 {
        u64 size_af, size_bf;
 
-       size_af = 0xFFFFFFFF - mc->vram_end;
-       size_bf = mc->vram_start;
+       size_af = ((0xFFFFFFFF - mc->vram_end) + mc->gtt_base_align) & ~mc->gtt_base_align;
+       size_bf = mc->vram_start & ~mc->gtt_base_align;
        if (size_bf > size_af) {
                if (mc->gtt_size > size_bf) {
                        dev_warn(rdev->dev, "limiting GTT\n");
                        mc->gtt_size = size_bf;
                }
-               mc->gtt_start = mc->vram_start - mc->gtt_size;
+               mc->gtt_start = (mc->vram_start & ~mc->gtt_base_align) - mc->gtt_size;
        } else {
                if (mc->gtt_size > size_af) {
                        dev_warn(rdev->dev, "limiting GTT\n");
                        mc->gtt_size = size_af;
                }
-               mc->gtt_start = mc->vram_end + 1;
+               mc->gtt_start = (mc->vram_end + 1 + mc->gtt_base_align) & ~mc->gtt_base_align;
        }
        mc->gtt_end = mc->gtt_start + mc->gtt_size - 1;
        dev_info(rdev->dev, "GTT: %lluM 0x%08llX - 0x%08llX\n",
 
        }
        if (rdev->family == CHIP_RS400 || rdev->family == CHIP_RS480) {
                /* FIXME: RS400 & RS480 seems to have issue with GART size
-                * if 4G of system memory (needs more testing) */
+                * if 4G of system memory (needs more testing)
+                */
+               /* XXX is this still an issue with proper alignment? */
                rdev->mc.gtt_size = 32 * 1024 * 1024;
                DRM_ERROR("Forcing to 32M GART size (because of ASIC bug ?)\n");
        }
        r100_vram_init_sizes(rdev);
        base = (RREG32(RADEON_NB_TOM) & 0xffff) << 16;
        radeon_vram_location(rdev, &rdev->mc, base);
+       rdev->mc.gtt_base_align = rdev->mc.gtt_size - 1;
        radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);
 }
 
        base = G_000004_MC_FB_START(base) << 16;
        rdev->mc.igp_sideport_enabled = radeon_atombios_sideport_present(rdev);
        radeon_vram_location(rdev, &rdev->mc, base);
+       rdev->mc.gtt_base_align = 0;
        radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);
 }
 
        rs690_pm_info(rdev);
        rdev->mc.igp_sideport_enabled = radeon_atombios_sideport_present(rdev);
        radeon_vram_location(rdev, &rdev->mc, base);
+       rdev->mc.gtt_base_align = rdev->mc.gtt_size - 1;
        radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);
 }
 
        rv515_vram_get_type(rdev);
        r100_vram_init_sizes(rdev);
        radeon_vram_location(rdev, &rdev->mc, 0);
+       rdev->mc.gtt_base_align = 0;
        if (!(rdev->flags & RADEON_IS_AGP))
                radeon_gtt_location(rdev, &rdev->mc);
        radeon_update_bandwidth_info(rdev);